linux/fs/exec.c
Linus Torvalds d579c468d7 tracing updates for 6.4:
- User events are finally ready!
   After lots of collaboration between various parties, we finally locked
   down on a stable interface for user events that can also work with user
   space only tracing. This is implemented by telling the kernel (or user
   space library, but that part is user space only and not part of this
   patch set), where the variable is that the application uses to know if
   something is listening to the trace. There's also an interface to tell
   the kernel about these events, which will show up in the
   /sys/kernel/tracing/events/user_events/ directory, where it can be
    enabled. When it's enabled, the kernel will update the variable, to tell
   the application to start writing to the kernel.
   See https://lwn.net/Articles/927595/
 
 - Cleaned up the direct trampolines code to simplify arm64 addition of
   direct trampolines. Direct trampolines use the ftrace interface but
   instead of jumping to the ftrace trampoline, applications (mostly BPF)
   can register their own trampoline for performance reasons.
 
 - Some updates to the fprobe infrastructure. fprobes are more efficient than
   kprobes, as it does not need to save all the registers that kprobes on
   ftrace do. More work needs to be done before the fprobes will be exposed
   as dynamic events.
 
 - More updates to references to the obsolete path of
   /sys/kernel/debug/tracing for the new /sys/kernel/tracing path.
 
 - Add a seq_buf_do_printk() helper to seq_bufs, to print a large buffer line
   by line instead of all at once. There's users in production kernels that
   have a large data dump that originally used printk() directly, but the
   data dump was larger than what printk() allowed as a single print.
   Using seq_buf() to do the printing fixes that.
 
 - Add /sys/kernel/tracing/touched_functions that shows all functions that
   was every traced by ftrace or a direct trampoline. This is used for
   debugging issues where a traced function could have caused a crash by
   a bpf program or live patching.
 
 - Add a "fields" option that is similar to "raw" but outputs the fields of
   the events. It's easier to read by humans.
 
 - Some minor fixes and clean ups.
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Merge tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing updates from Steven Rostedt:

 - User events are finally ready!

   After lots of collaboration between various parties, we finally
   locked down on a stable interface for user events that can also work
   with user space only tracing.

   This is implemented by telling the kernel (or user space library, but
   that part is user space only and not part of this patch set), where
   the variable is that the application uses to know if something is
   listening to the trace.

   There's also an interface to tell the kernel about these events,
   which will show up in the /sys/kernel/tracing/events/user_events/
   directory, where it can be enabled.

   When it's enabled, the kernel will update the variable, to tell the
   application to start writing to the kernel.

   See https://lwn.net/Articles/927595/

 - Cleaned up the direct trampolines code to simplify arm64 addition of
   direct trampolines.

   Direct trampolines use the ftrace interface but instead of jumping to
   the ftrace trampoline, applications (mostly BPF) can register their
   own trampoline for performance reasons.

 - Some updates to the fprobe infrastructure. fprobes are more efficient
   than kprobes, as it does not need to save all the registers that
   kprobes on ftrace do. More work needs to be done before the fprobes
   will be exposed as dynamic events.

 - More updates to references to the obsolete path of
   /sys/kernel/debug/tracing for the new /sys/kernel/tracing path.

 - Add a seq_buf_do_printk() helper to seq_bufs, to print a large buffer
   line by line instead of all at once.

   There are users in production kernels that have a large data dump
   that originally used printk() directly, but the data dump was larger
   than what printk() allowed as a single print.

   Using seq_buf() to do the printing fixes that.

 - Add /sys/kernel/tracing/touched_functions that shows all functions
   that was every traced by ftrace or a direct trampoline. This is used
   for debugging issues where a traced function could have caused a
   crash by a bpf program or live patching.

 - Add a "fields" option that is similar to "raw" but outputs the fields
   of the events. It's easier to read by humans.

 - Some minor fixes and clean ups.

* tag 'trace-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (41 commits)
  ring-buffer: Sync IRQ works before buffer destruction
  tracing: Add missing spaces in trace_print_hex_seq()
  ring-buffer: Ensure proper resetting of atomic variables in ring_buffer_reset_online_cpus
  recordmcount: Fix memory leaks in the uwrite function
  tracing/user_events: Limit max fault-in attempts
  tracing/user_events: Prevent same address and bit per process
  tracing/user_events: Ensure bit is cleared on unregister
  tracing/user_events: Ensure write index cannot be negative
  seq_buf: Add seq_buf_do_printk() helper
  tracing: Fix print_fields() for __dyn_loc/__rel_loc
  tracing/user_events: Set event filter_type from type
  ring-buffer: Clearly check null ptr returned by rb_set_head_page()
  tracing: Unbreak user events
  tracing/user_events: Use print_format_fields() for trace output
  tracing/user_events: Align structs with tabs for readability
  tracing/user_events: Limit global user_event count
  tracing/user_events: Charge event allocs to cgroups
  tracing/user_events: Update documentation for ABI
  tracing/user_events: Use write ABI in example
  tracing/user_events: Add ABI self-test
  ...
2023-04-28 15:57:53 -07:00

2179 lines
52 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/exec.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* #!-checking implemented by tytso.
*/
/*
* Demand-loading implemented 01.12.91 - no need to read anything but
* the header into memory. The inode of the executable is put into
* "current->executable", and page faults do the actual loading. Clean.
*
* Once more I can proudly say that linux stood up to being changed: it
* was less than 2 hours work to get demand-loading completely implemented.
*
* Demand loading changed July 1993 by Eric Youngdale. Use mmap instead,
* current->executable is only used by the procfs. This allows a dispatch
* table to check for several different types of binary formats. We keep
* trying until we recognize the file or we run out of supported binary
* formats.
*/
#include <linux/kernel_read_file.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/swap.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/signal.h>
#include <linux/sched/numa_balancing.h>
#include <linux/sched/task.h>
#include <linux/pagemap.h>
#include <linux/perf_event.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/kmod.h>
#include <linux/fsnotify.h>
#include <linux/fs_struct.h>
#include <linux/oom.h>
#include <linux/compat.h>
#include <linux/vmalloc.h>
#include <linux/io_uring.h>
#include <linux/syscall_user_dispatch.h>
#include <linux/coredump.h>
#include <linux/time_namespace.h>
#include <linux/user_events.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
#include <trace/events/task.h>
#include "internal.h"
#include <trace/events/sched.h>
static int bprm_creds_from_file(struct linux_binprm *bprm);
int suid_dumpable = 0;
static LIST_HEAD(formats);
static DEFINE_RWLOCK(binfmt_lock);
void __register_binfmt(struct linux_binfmt * fmt, int insert)
{
write_lock(&binfmt_lock);
insert ? list_add(&fmt->lh, &formats) :
list_add_tail(&fmt->lh, &formats);
write_unlock(&binfmt_lock);
}
EXPORT_SYMBOL(__register_binfmt);
void unregister_binfmt(struct linux_binfmt * fmt)
{
write_lock(&binfmt_lock);
list_del(&fmt->lh);
write_unlock(&binfmt_lock);
}
EXPORT_SYMBOL(unregister_binfmt);
static inline void put_binfmt(struct linux_binfmt * fmt)
{
module_put(fmt->module);
}
bool path_noexec(const struct path *path)
{
return (path->mnt->mnt_flags & MNT_NOEXEC) ||
(path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
}
#ifdef CONFIG_USELIB
/*
* Note that a shared library must be both readable and executable due to
* security reasons.
*
* Also note that we take the address to load from the file itself.
*/
SYSCALL_DEFINE1(uselib, const char __user *, library)
{
struct linux_binfmt *fmt;
struct file *file;
struct filename *tmp = getname(library);
int error = PTR_ERR(tmp);
static const struct open_flags uselib_flags = {
.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
.acc_mode = MAY_READ | MAY_EXEC,
.intent = LOOKUP_OPEN,
.lookup_flags = LOOKUP_FOLLOW,
};
if (IS_ERR(tmp))
goto out;
file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
putname(tmp);
error = PTR_ERR(file);
if (IS_ERR(file))
goto out;
/*
* may_open() has already checked for this, so it should be
* impossible to trip now. But we need to be extra cautious
* and check again at the very end too.
*/
error = -EACCES;
if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
path_noexec(&file->f_path)))
goto exit;
fsnotify_open(file);
error = -ENOEXEC;
read_lock(&binfmt_lock);
list_for_each_entry(fmt, &formats, lh) {
if (!fmt->load_shlib)
continue;
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
error = fmt->load_shlib(file);
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (error != -ENOEXEC)
break;
}
read_unlock(&binfmt_lock);
exit:
fput(file);
out:
return error;
}
#endif /* #ifdef CONFIG_USELIB */
#ifdef CONFIG_MMU
/*
* The nascent bprm->mm is not visible until exec_mmap() but it can
* use a lot of memory, account these pages in current->mm temporary
* for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
* change the counter back via acct_arg_size(0).
*/
static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
{
struct mm_struct *mm = current->mm;
long diff = (long)(pages - bprm->vma_pages);
if (!mm || !diff)
return;
bprm->vma_pages = pages;
add_mm_counter(mm, MM_ANONPAGES, diff);
}
static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
int write)
{
struct page *page;
int ret;
unsigned int gup_flags = 0;
#ifdef CONFIG_STACK_GROWSUP
if (write) {
ret = expand_downwards(bprm->vma, pos);
if (ret < 0)
return NULL;
}
#endif
if (write)
gup_flags |= FOLL_WRITE;
/*
* We are doing an exec(). 'current' is the process
* doing the exec and bprm->mm is the new process's mm.
*/
mmap_read_lock(bprm->mm);
ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags,
&page, NULL, NULL);
mmap_read_unlock(bprm->mm);
if (ret <= 0)
return NULL;
if (write)
acct_arg_size(bprm, vma_pages(bprm->vma));
return page;
}
static void put_arg_page(struct page *page)
{
put_page(page);
}
static void free_arg_pages(struct linux_binprm *bprm)
{
}
static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
struct page *page)
{
flush_cache_page(bprm->vma, pos, page_to_pfn(page));
}
static int __bprm_mm_init(struct linux_binprm *bprm)
{
int err;
struct vm_area_struct *vma = NULL;
struct mm_struct *mm = bprm->mm;
bprm->vma = vma = vm_area_alloc(mm);
if (!vma)
return -ENOMEM;
vma_set_anonymous(vma);
if (mmap_write_lock_killable(mm)) {
err = -EINTR;
goto err_free;
}
/*
* Place the stack at the largest stack address the architecture
* supports. Later, we'll move this to an appropriate place. We don't
* use STACK_TOP because that can depend on attributes which aren't
* configured yet.
*/
BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
vma->vm_end = STACK_TOP_MAX;
vma->vm_start = vma->vm_end - PAGE_SIZE;
vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP);
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
err = insert_vm_struct(mm, vma);
if (err)
goto err;
mm->stack_vm = mm->total_vm = 1;
mmap_write_unlock(mm);
bprm->p = vma->vm_end - sizeof(void *);
return 0;
err:
mmap_write_unlock(mm);
err_free:
bprm->vma = NULL;
vm_area_free(vma);
return err;
}
static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
return len <= MAX_ARG_STRLEN;
}
#else
static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
{
}
static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
int write)
{
struct page *page;
page = bprm->page[pos / PAGE_SIZE];
if (!page && write) {
page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
if (!page)
return NULL;
bprm->page[pos / PAGE_SIZE] = page;
}
return page;
}
static void put_arg_page(struct page *page)
{
}
static void free_arg_page(struct linux_binprm *bprm, int i)
{
if (bprm->page[i]) {
__free_page(bprm->page[i]);
bprm->page[i] = NULL;
}
}
static void free_arg_pages(struct linux_binprm *bprm)
{
int i;
for (i = 0; i < MAX_ARG_PAGES; i++)
free_arg_page(bprm, i);
}
static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
struct page *page)
{
}
static int __bprm_mm_init(struct linux_binprm *bprm)
{
bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
return 0;
}
static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
return len <= bprm->p;
}
#endif /* CONFIG_MMU */
/*
* Create a new mm_struct and populate it with a temporary stack
* vm_area_struct. We don't have enough context at this point to set the stack
* flags, permissions, and offset, so we use temporary values. We'll update
* them later in setup_arg_pages().
*/
static int bprm_mm_init(struct linux_binprm *bprm)
{
int err;
struct mm_struct *mm = NULL;
bprm->mm = mm = mm_alloc();
err = -ENOMEM;
if (!mm)
goto err;
/* Save current stack limit for all calculations made during exec. */
task_lock(current->group_leader);
bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
task_unlock(current->group_leader);
err = __bprm_mm_init(bprm);
if (err)
goto err;
return 0;
err:
if (mm) {
bprm->mm = NULL;
mmdrop(mm);
}
return err;
}
struct user_arg_ptr {
#ifdef CONFIG_COMPAT
bool is_compat;
#endif
union {
const char __user *const __user *native;
#ifdef CONFIG_COMPAT
const compat_uptr_t __user *compat;
#endif
} ptr;
};
static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
{
const char __user *native;
#ifdef CONFIG_COMPAT
if (unlikely(argv.is_compat)) {
compat_uptr_t compat;
if (get_user(compat, argv.ptr.compat + nr))
return ERR_PTR(-EFAULT);
return compat_ptr(compat);
}
#endif
if (get_user(native, argv.ptr.native + nr))
return ERR_PTR(-EFAULT);
return native;
}
/*
* count() counts the number of strings in array ARGV.
*/
static int count(struct user_arg_ptr argv, int max)
{
int i = 0;
if (argv.ptr.native != NULL) {
for (;;) {
const char __user *p = get_user_arg_ptr(argv, i);
if (!p)
break;
if (IS_ERR(p))
return -EFAULT;
if (i >= max)
return -E2BIG;
++i;
if (fatal_signal_pending(current))
return -ERESTARTNOHAND;
cond_resched();
}
}
return i;
}
static int count_strings_kernel(const char *const *argv)
{
int i;
if (!argv)
return 0;
for (i = 0; argv[i]; ++i) {
if (i >= MAX_ARG_STRINGS)
return -E2BIG;
if (fatal_signal_pending(current))
return -ERESTARTNOHAND;
cond_resched();
}
return i;
}
static int bprm_stack_limits(struct linux_binprm *bprm)
{
unsigned long limit, ptr_size;
/*
* Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
* (whichever is smaller) for the argv+env strings.
* This ensures that:
* - the remaining binfmt code will not run out of stack space,
* - the program will have a reasonable amount of stack left
* to work from.
*/
limit = _STK_LIM / 4 * 3;
limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
/*
* We've historically supported up to 32 pages (ARG_MAX)
* of argument strings even with small stacks
*/
limit = max_t(unsigned long, limit, ARG_MAX);
/*
* We must account for the size of all the argv and envp pointers to
* the argv and envp strings, since they will also take up space in
* the stack. They aren't stored until much later when we can't
* signal to the parent that the child has run out of stack space.
* Instead, calculate it here so it's possible to fail gracefully.
*
* In the case of argc = 0, make sure there is space for adding a
* empty string (which will bump argc to 1), to ensure confused
* userspace programs don't start processing from argv[1], thinking
* argc can never be 0, to keep them from walking envp by accident.
* See do_execveat_common().
*/
ptr_size = (max(bprm->argc, 1) + bprm->envc) * sizeof(void *);
if (limit <= ptr_size)
return -E2BIG;
limit -= ptr_size;
bprm->argmin = bprm->p - limit;
return 0;
}
/*
* 'copy_strings()' copies argument/environment strings from the old
* processes's memory to the new process's stack. The call to get_user_pages()
* ensures the destination page is created and not swapped out.
*/
static int copy_strings(int argc, struct user_arg_ptr argv,
struct linux_binprm *bprm)
{
struct page *kmapped_page = NULL;
char *kaddr = NULL;
unsigned long kpos = 0;
int ret;
while (argc-- > 0) {
const char __user *str;
int len;
unsigned long pos;
ret = -EFAULT;
str = get_user_arg_ptr(argv, argc);
if (IS_ERR(str))
goto out;
len = strnlen_user(str, MAX_ARG_STRLEN);
if (!len)
goto out;
ret = -E2BIG;
if (!valid_arg_len(bprm, len))
goto out;
/* We're going to work our way backwards. */
pos = bprm->p;
str += len;
bprm->p -= len;
#ifdef CONFIG_MMU
if (bprm->p < bprm->argmin)
goto out;
#endif
while (len > 0) {
int offset, bytes_to_copy;
if (fatal_signal_pending(current)) {
ret = -ERESTARTNOHAND;
goto out;
}
cond_resched();
offset = pos % PAGE_SIZE;
if (offset == 0)
offset = PAGE_SIZE;
bytes_to_copy = offset;
if (bytes_to_copy > len)
bytes_to_copy = len;
offset -= bytes_to_copy;
pos -= bytes_to_copy;
str -= bytes_to_copy;
len -= bytes_to_copy;
if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
struct page *page;
page = get_arg_page(bprm, pos, 1);
if (!page) {
ret = -E2BIG;
goto out;
}
if (kmapped_page) {
flush_dcache_page(kmapped_page);
kunmap_local(kaddr);
put_arg_page(kmapped_page);
}
kmapped_page = page;
kaddr = kmap_local_page(kmapped_page);
kpos = pos & PAGE_MASK;
flush_arg_page(bprm, kpos, kmapped_page);
}
if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
ret = -EFAULT;
goto out;
}
}
}
ret = 0;
out:
if (kmapped_page) {
flush_dcache_page(kmapped_page);
kunmap_local(kaddr);
put_arg_page(kmapped_page);
}
return ret;
}
/*
* Copy and argument/environment string from the kernel to the processes stack.
*/
int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
{
int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
unsigned long pos = bprm->p;
if (len == 0)
return -EFAULT;
if (!valid_arg_len(bprm, len))
return -E2BIG;
/* We're going to work our way backwards. */
arg += len;
bprm->p -= len;
if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
return -E2BIG;
while (len > 0) {
unsigned int bytes_to_copy = min_t(unsigned int, len,
min_not_zero(offset_in_page(pos), PAGE_SIZE));
struct page *page;
pos -= bytes_to_copy;
arg -= bytes_to_copy;
len -= bytes_to_copy;
page = get_arg_page(bprm, pos, 1);
if (!page)
return -E2BIG;
flush_arg_page(bprm, pos & PAGE_MASK, page);
memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
put_arg_page(page);
}
return 0;
}
EXPORT_SYMBOL(copy_string_kernel);
static int copy_strings_kernel(int argc, const char *const *argv,
struct linux_binprm *bprm)
{
while (argc-- > 0) {
int ret = copy_string_kernel(argv[argc], bprm);
if (ret < 0)
return ret;
if (fatal_signal_pending(current))
return -ERESTARTNOHAND;
cond_resched();
}
return 0;
}
#ifdef CONFIG_MMU
/*
* During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
* the binfmt code determines where the new stack should reside, we shift it to
* its final location. The process proceeds as follows:
*
* 1) Use shift to calculate the new vma endpoints.
* 2) Extend vma to cover both the old and new ranges. This ensures the
* arguments passed to subsequent functions are consistent.
* 3) Move vma's page tables to the new range.
* 4) Free up any cleared pgd range.
* 5) Shrink the vma to cover only the new range.
*/
static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long old_start = vma->vm_start;
unsigned long old_end = vma->vm_end;
unsigned long length = old_end - old_start;
unsigned long new_start = old_start - shift;
unsigned long new_end = old_end - shift;
VMA_ITERATOR(vmi, mm, new_start);
struct vm_area_struct *next;
struct mmu_gather tlb;
BUG_ON(new_start > new_end);
/*
* ensure there are no vmas between where we want to go
* and where we are
*/
if (vma != vma_next(&vmi))
return -EFAULT;
/*
* cover the whole range: [new_start, old_end)
*/
if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL))
return -ENOMEM;
/*
* move the page tables downwards, on failure we rely on
* process cleanup to remove whatever mess we made.
*/
if (length != move_page_tables(vma, old_start,
vma, new_start, length, false))
return -ENOMEM;
lru_add_drain();
tlb_gather_mmu(&tlb, mm);
next = vma_next(&vmi);
if (new_end > old_start) {
/*
* when the old and new regions overlap clear from new_end.
*/
free_pgd_range(&tlb, new_end, old_end, new_end,
next ? next->vm_start : USER_PGTABLES_CEILING);
} else {
/*
* otherwise, clean from old_start; this is done to not touch
* the address space in [new_end, old_start) some architectures
* have constraints on va-space that make this illegal (IA64) -
* for the others its just a little faster.
*/
free_pgd_range(&tlb, old_start, old_end, new_end,
next ? next->vm_start : USER_PGTABLES_CEILING);
}
tlb_finish_mmu(&tlb);
vma_prev(&vmi);
/* Shrink the vma to just the new range */
return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);
}
/*
* Finalizes the stack vm_area_struct. The flags and permissions are updated,
* the stack is optionally relocated, and some extra space is added.
*/
int setup_arg_pages(struct linux_binprm *bprm,
unsigned long stack_top,
int executable_stack)
{
unsigned long ret;
unsigned long stack_shift;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = bprm->vma;
struct vm_area_struct *prev = NULL;
unsigned long vm_flags;
unsigned long stack_base;
unsigned long stack_size;
unsigned long stack_expand;
unsigned long rlim_stack;
struct mmu_gather tlb;
struct vma_iterator vmi;
#ifdef CONFIG_STACK_GROWSUP
/* Limit stack size */
stack_base = bprm->rlim_stack.rlim_max;
stack_base = calc_max_stack_size(stack_base);
/* Add space for stack randomization. */
stack_base += (STACK_RND_MASK << PAGE_SHIFT);
/* Make sure we didn't let the argument array grow too large. */
if (vma->vm_end - vma->vm_start > stack_base)
return -ENOMEM;
stack_base = PAGE_ALIGN(stack_top - stack_base);
stack_shift = vma->vm_start - stack_base;
mm->arg_start = bprm->p - stack_shift;
bprm->p = vma->vm_end - stack_shift;
#else
stack_top = arch_align_stack(stack_top);
stack_top = PAGE_ALIGN(stack_top);
if (unlikely(stack_top < mmap_min_addr) ||
unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
return -ENOMEM;
stack_shift = vma->vm_end - stack_top;
bprm->p -= stack_shift;
mm->arg_start = bprm->p;
#endif
if (bprm->loader)
bprm->loader -= stack_shift;
bprm->exec -= stack_shift;
if (mmap_write_lock_killable(mm))
return -EINTR;
vm_flags = VM_STACK_FLAGS;
/*
* Adjust stack execute permissions; explicitly enable for
* EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
* (arch default) otherwise.
*/
if (unlikely(executable_stack == EXSTACK_ENABLE_X))
vm_flags |= VM_EXEC;
else if (executable_stack == EXSTACK_DISABLE_X)
vm_flags &= ~VM_EXEC;
vm_flags |= mm->def_flags;
vm_flags |= VM_STACK_INCOMPLETE_SETUP;
vma_iter_init(&vmi, mm, vma->vm_start);
tlb_gather_mmu(&tlb, mm);
ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
vm_flags);
tlb_finish_mmu(&tlb);
if (ret)
goto out_unlock;
BUG_ON(prev != vma);
if (unlikely(vm_flags & VM_EXEC)) {
pr_warn_once("process '%pD4' started with executable stack\n",
bprm->file);
}
/* Move stack pages down in memory. */
if (stack_shift) {
ret = shift_arg_pages(vma, stack_shift);
if (ret)
goto out_unlock;
}
/* mprotect_fixup is overkill to remove the temporary stack flags */
vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
stack_size = vma->vm_end - vma->vm_start;
/*
* Align this down to a page boundary as expand_stack
* will align it up.
*/
rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
stack_expand = min(rlim_stack, stack_size + stack_expand);
#ifdef CONFIG_STACK_GROWSUP
stack_base = vma->vm_start + stack_expand;
#else
stack_base = vma->vm_end - stack_expand;
#endif
current->mm->start_stack = bprm->p;
ret = expand_stack(vma, stack_base);
if (ret)
ret = -EFAULT;
out_unlock:
mmap_write_unlock(mm);
return ret;
}
EXPORT_SYMBOL(setup_arg_pages);
#else
/*
* Transfer the program arguments and environment from the holding pages
* onto the stack. The provided stack pointer is adjusted accordingly.
*/
int transfer_args_to_stack(struct linux_binprm *bprm,
unsigned long *sp_location)
{
unsigned long index, stop, sp;
int ret = 0;
stop = bprm->p >> PAGE_SHIFT;
sp = *sp_location;
for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
char *src = kmap_local_page(bprm->page[index]) + offset;
sp -= PAGE_SIZE - offset;
if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
ret = -EFAULT;
kunmap_local(src);
if (ret)
goto out;
}
*sp_location = sp;
out:
return ret;
}
EXPORT_SYMBOL(transfer_args_to_stack);
#endif /* CONFIG_MMU */
static struct file *do_open_execat(int fd, struct filename *name, int flags)
{
struct file *file;
int err;
struct open_flags open_exec_flags = {
.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
.acc_mode = MAY_EXEC,
.intent = LOOKUP_OPEN,
.lookup_flags = LOOKUP_FOLLOW,
};
if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
return ERR_PTR(-EINVAL);
if (flags & AT_SYMLINK_NOFOLLOW)
open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
if (flags & AT_EMPTY_PATH)
open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
file = do_filp_open(fd, name, &open_exec_flags);
if (IS_ERR(file))
goto out;
/*
* may_open() has already checked for this, so it should be
* impossible to trip now. But we need to be extra cautious
* and check again at the very end too.
*/
err = -EACCES;
if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
path_noexec(&file->f_path)))
goto exit;
err = deny_write_access(file);
if (err)
goto exit;
if (name->name[0] != '\0')
fsnotify_open(file);
out:
return file;
exit:
fput(file);
return ERR_PTR(err);
}
struct file *open_exec(const char *name)
{
struct filename *filename = getname_kernel(name);
struct file *f = ERR_CAST(filename);
if (!IS_ERR(filename)) {
f = do_open_execat(AT_FDCWD, filename, 0);
putname(filename);
}
return f;
}
EXPORT_SYMBOL(open_exec);
#if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
{
ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
if (res > 0)
flush_icache_user_range(addr, addr + len);
return res;
}
EXPORT_SYMBOL(read_code);
#endif
/*
* Maps the mm_struct mm into the current task struct.
* On success, this function returns with exec_update_lock
* held for writing.
*/
static int exec_mmap(struct mm_struct *mm)
{
struct task_struct *tsk;
struct mm_struct *old_mm, *active_mm;
int ret;
/* Notify parent that we're no longer interested in the old VM */
tsk = current;
old_mm = current->mm;
exec_mm_release(tsk, old_mm);
if (old_mm)
sync_mm_rss(old_mm);
ret = down_write_killable(&tsk->signal->exec_update_lock);
if (ret)
return ret;
if (old_mm) {
/*
* If there is a pending fatal signal perhaps a signal
* whose default action is to create a coredump get
* out and die instead of going through with the exec.
*/
ret = mmap_read_lock_killable(old_mm);
if (ret) {
up_write(&tsk->signal->exec_update_lock);
return ret;
}
}
task_lock(tsk);
membarrier_exec_mmap(mm);
local_irq_disable();
active_mm = tsk->active_mm;
tsk->active_mm = mm;
tsk->mm = mm;
mm_init_cid(mm);
/*
* This prevents preemption while active_mm is being loaded and
* it and mm are being updated, which could cause problems for
* lazy tlb mm refcounting when these are updated by context
* switches. Not all architectures can handle irqs off over
* activate_mm yet.
*/
if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
local_irq_enable();
activate_mm(active_mm, mm);
if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
local_irq_enable();
lru_gen_add_mm(mm);
task_unlock(tsk);
lru_gen_use_mm(mm);
if (old_mm) {
mmap_read_unlock(old_mm);
BUG_ON(active_mm != old_mm);
setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
mm_update_next_owner(old_mm);
mmput(old_mm);
return 0;
}
mmdrop_lazy_tlb(active_mm);
return 0;
}
static int de_thread(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
struct sighand_struct *oldsighand = tsk->sighand;
spinlock_t *lock = &oldsighand->siglock;
if (thread_group_empty(tsk))
goto no_thread_group;
/*
* Kill all other threads in the thread group.
*/
spin_lock_irq(lock);
if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
/*
* Another group action in progress, just
* return so that the signal is processed.
*/
spin_unlock_irq(lock);
return -EAGAIN;
}
sig->group_exec_task = tsk;
sig->notify_count = zap_other_threads(tsk);
if (!thread_group_leader(tsk))
sig->notify_count--;
while (sig->notify_count) {
__set_current_state(TASK_KILLABLE);
spin_unlock_irq(lock);
schedule();
if (__fatal_signal_pending(tsk))
goto killed;
spin_lock_irq(lock);
}
spin_unlock_irq(lock);
/*
* At this point all other threads have exited, all we have to
* do is to wait for the thread group leader to become inactive,
* and to assume its PID:
*/
if (!thread_group_leader(tsk)) {
struct task_struct *leader = tsk->group_leader;
for (;;) {
cgroup_threadgroup_change_begin(tsk);
write_lock_irq(&tasklist_lock);
/*
* Do this under tasklist_lock to ensure that
* exit_notify() can't miss ->group_exec_task
*/
sig->notify_count = -1;
if (likely(leader->exit_state))
break;
__set_current_state(TASK_KILLABLE);
write_unlock_irq(&tasklist_lock);
cgroup_threadgroup_change_end(tsk);
schedule();
if (__fatal_signal_pending(tsk))
goto killed;
}
/*
* The only record we have of the real-time age of a
* process, regardless of execs it's done, is start_time.
* All the past CPU time is accumulated in signal_struct
* from sister threads now dead. But in this non-leader
* exec, nothing survives from the original leader thread,
* whose birth marks the true age of this process now.
* When we take on its identity by switching to its PID, we
* also take its birthdate (always earlier than our own).
*/
tsk->start_time = leader->start_time;
tsk->start_boottime = leader->start_boottime;
BUG_ON(!same_thread_group(leader, tsk));
/*
* An exec() starts a new thread group with the
* TGID of the previous thread group. Rehash the
* two threads with a switched PID, and release
* the former thread group leader:
*/
/* Become a process group leader with the old leader's pid.
* The old leader becomes a thread of the this thread group.
*/
exchange_tids(tsk, leader);
transfer_pid(leader, tsk, PIDTYPE_TGID);
transfer_pid(leader, tsk, PIDTYPE_PGID);
transfer_pid(leader, tsk, PIDTYPE_SID);
list_replace_rcu(&leader->tasks, &tsk->tasks);
list_replace_init(&leader->sibling, &tsk->sibling);
tsk->group_leader = tsk;
leader->group_leader = tsk;
tsk->exit_signal = SIGCHLD;
leader->exit_signal = -1;
BUG_ON(leader->exit_state != EXIT_ZOMBIE);
leader->exit_state = EXIT_DEAD;
/*
* We are going to release_task()->ptrace_unlink() silently,
* the tracer can sleep in do_wait(). EXIT_DEAD guarantees
* the tracer won't block again waiting for this thread.
*/
if (unlikely(leader->ptrace))
__wake_up_parent(leader, leader->parent);
write_unlock_irq(&tasklist_lock);
cgroup_threadgroup_change_end(tsk);
release_task(leader);
}
sig->group_exec_task = NULL;
sig->notify_count = 0;
no_thread_group:
/* we have changed execution domain */
tsk->exit_signal = SIGCHLD;
BUG_ON(!thread_group_leader(tsk));
return 0;
killed:
/* protects against exit_notify() and __exit_signal() */
read_lock(&tasklist_lock);
sig->group_exec_task = NULL;
sig->notify_count = 0;
read_unlock(&tasklist_lock);
return -EAGAIN;
}
/*
* This function makes sure the current process has its own signal table,
* so that flush_signal_handlers can later reset the handlers without
* disturbing other processes. (Other processes might share the signal
* table via the CLONE_SIGHAND option to clone().)
*/
static int unshare_sighand(struct task_struct *me)
{
struct sighand_struct *oldsighand = me->sighand;
if (refcount_read(&oldsighand->count) != 1) {
struct sighand_struct *newsighand;
/*
* This ->sighand is shared with the CLONE_SIGHAND
* but not CLONE_THREAD task, switch to the new one.
*/
newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
if (!newsighand)
return -ENOMEM;
refcount_set(&newsighand->count, 1);
write_lock_irq(&tasklist_lock);
spin_lock(&oldsighand->siglock);
memcpy(newsighand->action, oldsighand->action,
sizeof(newsighand->action));
rcu_assign_pointer(me->sighand, newsighand);
spin_unlock(&oldsighand->siglock);
write_unlock_irq(&tasklist_lock);
__cleanup_sighand(oldsighand);
}
return 0;
}
char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
{
task_lock(tsk);
/* Always NUL terminated and zero-padded */
strscpy_pad(buf, tsk->comm, buf_size);
task_unlock(tsk);
return buf;
}
EXPORT_SYMBOL_GPL(__get_task_comm);
/*
* These functions flushes out all traces of the currently running executable
* so that a new one can be started
*/
void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
{
task_lock(tsk);
trace_task_rename(tsk, buf);
strscpy_pad(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
perf_event_comm(tsk, exec);
}
/*
* Calling this is the point of no return. None of the failures will be
* seen by userspace since either the process is already taking a fatal
* signal (via de_thread() or coredump), or will have SEGV raised
* (after exec_mmap()) by search_binary_handler (see below).
*/
int begin_new_exec(struct linux_binprm * bprm)
{
struct task_struct *me = current;
int retval;
/* Once we are committed compute the creds */
retval = bprm_creds_from_file(bprm);
if (retval)
return retval;
/*
* Ensure all future errors are fatal.
*/
bprm->point_of_no_return = true;
/*
* Make this the only thread in the thread group.
*/
retval = de_thread(me);
if (retval)
goto out;
/*
* Cancel any io_uring activity across execve
*/
io_uring_task_cancel();
/* Ensure the files table is not shared. */
retval = unshare_files();
if (retval)
goto out;
/*
* Must be called _before_ exec_mmap() as bprm->mm is
* not visible until then. This also enables the update
* to be lockless.
*/
retval = set_mm_exe_file(bprm->mm, bprm->file);
if (retval)
goto out;
/* If the binary is not readable then enforce mm->dumpable=0 */
would_dump(bprm, bprm->file);
if (bprm->have_execfd)
would_dump(bprm, bprm->executable);
/*
* Release all of the old mmap stuff
*/
acct_arg_size(bprm, 0);
retval = exec_mmap(bprm->mm);
if (retval)
goto out;
bprm->mm = NULL;
retval = exec_task_namespaces();
if (retval)
goto out_unlock;
#ifdef CONFIG_POSIX_TIMERS
spin_lock_irq(&me->sighand->siglock);
posix_cpu_timers_exit(me);
spin_unlock_irq(&me->sighand->siglock);
exit_itimers(me);
flush_itimer_signals();
#endif
/*
* Make the signal table private.
*/
retval = unshare_sighand(me);
if (retval)
goto out_unlock;
me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
PF_NOFREEZE | PF_NO_SETAFFINITY);
flush_thread();
me->personality &= ~bprm->per_clear;
clear_syscall_work_syscall_user_dispatch(me);
/*
* We have to apply CLOEXEC before we change whether the process is
* dumpable (in setup_new_exec) to avoid a race with a process in userspace
* trying to access the should-be-closed file descriptors of a process
* undergoing exec(2).
*/
do_close_on_exec(me->files);
if (bprm->secureexec) {
/* Make sure parent cannot signal privileged process. */
me->pdeath_signal = 0;
/*
* For secureexec, reset the stack limit to sane default to
* avoid bad behavior from the prior rlimits. This has to
* happen before arch_pick_mmap_layout(), which examines
* RLIMIT_STACK, but after the point of no return to avoid
* needing to clean up the change on failure.
*/
if (bprm->rlim_stack.rlim_cur > _STK_LIM)
bprm->rlim_stack.rlim_cur = _STK_LIM;
}
me->sas_ss_sp = me->sas_ss_size = 0;
/*
* Figure out dumpability. Note that this checking only of current
* is wrong, but userspace depends on it. This should be testing
* bprm->secureexec instead.
*/
if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
!(uid_eq(current_euid(), current_uid()) &&
gid_eq(current_egid(), current_gid())))
set_dumpable(current->mm, suid_dumpable);
else
set_dumpable(current->mm, SUID_DUMP_USER);
perf_event_exec();
__set_task_comm(me, kbasename(bprm->filename), true);
/* An exec changes our domain. We are no longer part of the thread
group */
WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
flush_signal_handlers(me, 0);
retval = set_cred_ucounts(bprm->cred);
if (retval < 0)
goto out_unlock;
/*
* install the new credentials for this executable
*/
security_bprm_committing_creds(bprm);
commit_creds(bprm->cred);
bprm->cred = NULL;
/*
* Disable monitoring for regular users
* when executing setuid binaries. Must
* wait until new credentials are committed
* by commit_creds() above
*/
if (get_dumpable(me->mm) != SUID_DUMP_USER)
perf_event_exit_task(me);
/*
* cred_guard_mutex must be held at least to this point to prevent
* ptrace_attach() from altering our determination of the task's
* credentials; any time after this it may be unlocked.
*/
security_bprm_committed_creds(bprm);
/* Pass the opened binary to the interpreter. */
if (bprm->have_execfd) {
retval = get_unused_fd_flags(0);
if (retval < 0)
goto out_unlock;
fd_install(retval, bprm->executable);
bprm->executable = NULL;
bprm->execfd = retval;
}
return 0;
out_unlock:
up_write(&me->signal->exec_update_lock);
out:
return retval;
}
EXPORT_SYMBOL(begin_new_exec);
void would_dump(struct linux_binprm *bprm, struct file *file)
{
struct inode *inode = file_inode(file);
struct mnt_idmap *idmap = file_mnt_idmap(file);
if (inode_permission(idmap, inode, MAY_READ) < 0) {
struct user_namespace *old, *user_ns;
bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
/* Ensure mm->user_ns contains the executable */
user_ns = old = bprm->mm->user_ns;
while ((user_ns != &init_user_ns) &&
!privileged_wrt_inode_uidgid(user_ns, idmap, inode))
user_ns = user_ns->parent;
if (old != user_ns) {
bprm->mm->user_ns = get_user_ns(user_ns);
put_user_ns(old);
}
}
}
EXPORT_SYMBOL(would_dump);
void setup_new_exec(struct linux_binprm * bprm)
{
/* Setup things that can depend upon the personality */
struct task_struct *me = current;
arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
arch_setup_new_exec();
/* Set the new mm task size. We have to do that late because it may
* depend on TIF_32BIT which is only updated in flush_thread() on
* some architectures like powerpc
*/
me->mm->task_size = TASK_SIZE;
up_write(&me->signal->exec_update_lock);
mutex_unlock(&me->signal->cred_guard_mutex);
}
EXPORT_SYMBOL(setup_new_exec);
/* Runs immediately before start_thread() takes over. */
void finalize_exec(struct linux_binprm *bprm)
{
/* Store any stack rlimit changes before starting thread. */
task_lock(current->group_leader);
current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
task_unlock(current->group_leader);
}
EXPORT_SYMBOL(finalize_exec);
/*
* Prepare credentials and lock ->cred_guard_mutex.
* setup_new_exec() commits the new creds and drops the lock.
* Or, if exec fails before, free_bprm() should release ->cred
* and unlock.
*/
static int prepare_bprm_creds(struct linux_binprm *bprm)
{
if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
return -ERESTARTNOINTR;
bprm->cred = prepare_exec_creds();
if (likely(bprm->cred))
return 0;
mutex_unlock(&current->signal->cred_guard_mutex);
return -ENOMEM;
}
static void free_bprm(struct linux_binprm *bprm)
{
if (bprm->mm) {
acct_arg_size(bprm, 0);
mmput(bprm->mm);
}
free_arg_pages(bprm);
if (bprm->cred) {
mutex_unlock(&current->signal->cred_guard_mutex);
abort_creds(bprm->cred);
}
if (bprm->file) {
allow_write_access(bprm->file);
fput(bprm->file);
}
if (bprm->executable)
fput(bprm->executable);
/* If a binfmt changed the interp, free it. */
if (bprm->interp != bprm->filename)
kfree(bprm->interp);
kfree(bprm->fdpath);
kfree(bprm);
}
static struct linux_binprm *alloc_bprm(int fd, struct filename *filename)
{
struct linux_binprm *bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
int retval = -ENOMEM;
if (!bprm)
goto out;
if (fd == AT_FDCWD || filename->name[0] == '/') {
bprm->filename = filename->name;
} else {
if (filename->name[0] == '\0')
bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
else
bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
fd, filename->name);
if (!bprm->fdpath)
goto out_free;
bprm->filename = bprm->fdpath;
}
bprm->interp = bprm->filename;
retval = bprm_mm_init(bprm);
if (retval)
goto out_free;
return bprm;
out_free:
free_bprm(bprm);
out:
return ERR_PTR(retval);
}
int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
{
/* If a binfmt changed the interp, free it first. */
if (bprm->interp != bprm->filename)
kfree(bprm->interp);
bprm->interp = kstrdup(interp, GFP_KERNEL);
if (!bprm->interp)
return -ENOMEM;
return 0;
}
EXPORT_SYMBOL(bprm_change_interp);
/*
* determine how safe it is to execute the proposed program
* - the caller must hold ->cred_guard_mutex to protect against
* PTRACE_ATTACH or seccomp thread-sync
*/
static void check_unsafe_exec(struct linux_binprm *bprm)
{
struct task_struct *p = current, *t;
unsigned n_fs;
if (p->ptrace)
bprm->unsafe |= LSM_UNSAFE_PTRACE;
/*
* This isn't strictly necessary, but it makes it harder for LSMs to
* mess up.
*/
if (task_no_new_privs(current))
bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
/*
* If another task is sharing our fs, we cannot safely
* suid exec because the differently privileged task
* will be able to manipulate the current directory, etc.
* It would be nice to force an unshare instead...
*/
t = p;
n_fs = 1;
spin_lock(&p->fs->lock);
rcu_read_lock();
while_each_thread(p, t) {
if (t->fs == p->fs)
n_fs++;
}
rcu_read_unlock();
if (p->fs->users > n_fs)
bprm->unsafe |= LSM_UNSAFE_SHARE;
else
p->fs->in_exec = 1;
spin_unlock(&p->fs->lock);
}
static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
{
/* Handle suid and sgid on files */
struct mnt_idmap *idmap;
struct inode *inode = file_inode(file);
unsigned int mode;
vfsuid_t vfsuid;
vfsgid_t vfsgid;
if (!mnt_may_suid(file->f_path.mnt))
return;
if (task_no_new_privs(current))
return;
mode = READ_ONCE(inode->i_mode);
if (!(mode & (S_ISUID|S_ISGID)))
return;
idmap = file_mnt_idmap(file);
/* Be careful if suid/sgid is set */
inode_lock(inode);
/* reload atomically mode/uid/gid now that lock held */
mode = inode->i_mode;
vfsuid = i_uid_into_vfsuid(idmap, inode);
vfsgid = i_gid_into_vfsgid(idmap, inode);
inode_unlock(inode);
/* We ignore suid/sgid if there are no mappings for them in the ns */
if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
!vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
return;
if (mode & S_ISUID) {
bprm->per_clear |= PER_CLEAR_ON_SETID;
bprm->cred->euid = vfsuid_into_kuid(vfsuid);
}
if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
bprm->per_clear |= PER_CLEAR_ON_SETID;
bprm->cred->egid = vfsgid_into_kgid(vfsgid);
}
}
/*
* Compute brpm->cred based upon the final binary.
*/
static int bprm_creds_from_file(struct linux_binprm *bprm)
{
/* Compute creds based on which file? */
struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
bprm_fill_uid(bprm, file);
return security_bprm_creds_from_file(bprm, file);
}
/*
* Fill the binprm structure from the inode.
* Read the first BINPRM_BUF_SIZE bytes
*
* This may be called multiple times for binary chains (scripts for example).
*/
static int prepare_binprm(struct linux_binprm *bprm)
{
loff_t pos = 0;
memset(bprm->buf, 0, BINPRM_BUF_SIZE);
return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
}
/*
* Arguments are '\0' separated strings found at the location bprm->p
* points to; chop off the first by relocating brpm->p to right after
* the first '\0' encountered.
*/
int remove_arg_zero(struct linux_binprm *bprm)
{
int ret = 0;
unsigned long offset;
char *kaddr;
struct page *page;
if (!bprm->argc)
return 0;
do {
offset = bprm->p & ~PAGE_MASK;
page = get_arg_page(bprm, bprm->p, 0);
if (!page) {
ret = -EFAULT;
goto out;
}
kaddr = kmap_local_page(page);
for (; offset < PAGE_SIZE && kaddr[offset];
offset++, bprm->p++)
;
kunmap_local(kaddr);
put_arg_page(page);
} while (offset == PAGE_SIZE);
bprm->p++;
bprm->argc--;
ret = 0;
out:
return ret;
}
EXPORT_SYMBOL(remove_arg_zero);
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
/*
* cycle the list of binary formats handler, until one recognizes the image
*/
static int search_binary_handler(struct linux_binprm *bprm)
{
bool need_retry = IS_ENABLED(CONFIG_MODULES);
struct linux_binfmt *fmt;
int retval;
retval = prepare_binprm(bprm);
if (retval < 0)
return retval;
retval = security_bprm_check(bprm);
if (retval)
return retval;
retval = -ENOENT;
retry:
read_lock(&binfmt_lock);
list_for_each_entry(fmt, &formats, lh) {
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
retval = fmt->load_binary(bprm);
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
read_unlock(&binfmt_lock);
return retval;
}
}
read_unlock(&binfmt_lock);
if (need_retry) {
if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
printable(bprm->buf[2]) && printable(bprm->buf[3]))
return retval;
if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
return retval;
need_retry = false;
goto retry;
}
return retval;
}
/* binfmt handlers will call back into begin_new_exec() on success. */
static int exec_binprm(struct linux_binprm *bprm)
{
pid_t old_pid, old_vpid;
int ret, depth;
/* Need to fetch pid before load_binary changes it */
old_pid = current->pid;
rcu_read_lock();
old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
rcu_read_unlock();
/* This allows 4 levels of binfmt rewrites before failing hard. */
for (depth = 0;; depth++) {
struct file *exec;
if (depth > 5)
return -ELOOP;
ret = search_binary_handler(bprm);
if (ret < 0)
return ret;
if (!bprm->interpreter)
break;
exec = bprm->file;
bprm->file = bprm->interpreter;
bprm->interpreter = NULL;
allow_write_access(exec);
if (unlikely(bprm->have_execfd)) {
if (bprm->executable) {
fput(exec);
return -ENOEXEC;
}
bprm->executable = exec;
} else
fput(exec);
}
audit_bprm(bprm);
trace_sched_process_exec(current, old_pid, bprm);
ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
proc_exec_connector(current);
return 0;
}
/*
* sys_execve() executes a new program.
*/
static int bprm_execve(struct linux_binprm *bprm,
int fd, struct filename *filename, int flags)
{
struct file *file;
int retval;
retval = prepare_bprm_creds(bprm);
if (retval)
return retval;
/*
* Check for unsafe execution states before exec_binprm(), which
* will call back into begin_new_exec(), into bprm_creds_from_file(),
* where setuid-ness is evaluated.
*/
check_unsafe_exec(bprm);
current->in_execve = 1;
sched_mm_cid_before_execve(current);
file = do_open_execat(fd, filename, flags);
retval = PTR_ERR(file);
if (IS_ERR(file))
goto out_unmark;
sched_exec();
bprm->file = file;
/*
* Record that a name derived from an O_CLOEXEC fd will be
* inaccessible after exec. This allows the code in exec to
* choose to fail when the executable is not mmaped into the
* interpreter and an open file descriptor is not passed to
* the interpreter. This makes for a better user experience
* than having the interpreter start and then immediately fail
* when it finds the executable is inaccessible.
*/
if (bprm->fdpath && get_close_on_exec(fd))
bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
/* Set the unchanging part of bprm->cred */
retval = security_bprm_creds_for_exec(bprm);
if (retval)
goto out;
retval = exec_binprm(bprm);
if (retval < 0)
goto out;
sched_mm_cid_after_execve(current);
/* execve succeeded */
current->fs->in_exec = 0;
current->in_execve = 0;
rseq_execve(current);
user_events_execve(current);
acct_update_integrals(current);
task_numa_free(current, false);
return retval;
out:
/*
* If past the point of no return ensure the code never
* returns to the userspace process. Use an existing fatal
* signal if present otherwise terminate the process with
* SIGSEGV.
*/
if (bprm->point_of_no_return && !fatal_signal_pending(current))
force_fatal_sig(SIGSEGV);
out_unmark:
sched_mm_cid_after_execve(current);
current->fs->in_exec = 0;
current->in_execve = 0;
return retval;
}
static int do_execveat_common(int fd, struct filename *filename,
struct user_arg_ptr argv,
struct user_arg_ptr envp,
int flags)
{
struct linux_binprm *bprm;
int retval;
if (IS_ERR(filename))
return PTR_ERR(filename);
/*
* We move the actual failure in case of RLIMIT_NPROC excess from
* set*uid() to execve() because too many poorly written programs
* don't check setuid() return code. Here we additionally recheck
* whether NPROC limit is still exceeded.
*/
if ((current->flags & PF_NPROC_EXCEEDED) &&
is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
retval = -EAGAIN;
goto out_ret;
}
/* We're below the limit (still or again), so we don't want to make
* further execve() calls fail. */
current->flags &= ~PF_NPROC_EXCEEDED;
bprm = alloc_bprm(fd, filename);
if (IS_ERR(bprm)) {
retval = PTR_ERR(bprm);
goto out_ret;
}
retval = count(argv, MAX_ARG_STRINGS);
if (retval == 0)
pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
current->comm, bprm->filename);
if (retval < 0)
goto out_free;
bprm->argc = retval;
retval = count(envp, MAX_ARG_STRINGS);
if (retval < 0)
goto out_free;
bprm->envc = retval;
retval = bprm_stack_limits(bprm);
if (retval < 0)
goto out_free;
retval = copy_string_kernel(bprm->filename, bprm);
if (retval < 0)
goto out_free;
bprm->exec = bprm->p;
retval = copy_strings(bprm->envc, envp, bprm);
if (retval < 0)
goto out_free;
retval = copy_strings(bprm->argc, argv, bprm);
if (retval < 0)
goto out_free;
/*
* When argv is empty, add an empty string ("") as argv[0] to
* ensure confused userspace programs that start processing
* from argv[1] won't end up walking envp. See also
* bprm_stack_limits().
*/
if (bprm->argc == 0) {
retval = copy_string_kernel("", bprm);
if (retval < 0)
goto out_free;
bprm->argc = 1;
}
retval = bprm_execve(bprm, fd, filename, flags);
out_free:
free_bprm(bprm);
out_ret:
putname(filename);
return retval;
}
int kernel_execve(const char *kernel_filename,
const char *const *argv, const char *const *envp)
{
struct filename *filename;
struct linux_binprm *bprm;
int fd = AT_FDCWD;
int retval;
/* It is non-sense for kernel threads to call execve */
if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
return -EINVAL;
filename = getname_kernel(kernel_filename);
if (IS_ERR(filename))
return PTR_ERR(filename);
bprm = alloc_bprm(fd, filename);
if (IS_ERR(bprm)) {
retval = PTR_ERR(bprm);
goto out_ret;
}
retval = count_strings_kernel(argv);
if (WARN_ON_ONCE(retval == 0))
retval = -EINVAL;
if (retval < 0)
goto out_free;
bprm->argc = retval;
retval = count_strings_kernel(envp);
if (retval < 0)
goto out_free;
bprm->envc = retval;
retval = bprm_stack_limits(bprm);
if (retval < 0)
goto out_free;
retval = copy_string_kernel(bprm->filename, bprm);
if (retval < 0)
goto out_free;
bprm->exec = bprm->p;
retval = copy_strings_kernel(bprm->envc, envp, bprm);
if (retval < 0)
goto out_free;
retval = copy_strings_kernel(bprm->argc, argv, bprm);
if (retval < 0)
goto out_free;
retval = bprm_execve(bprm, fd, filename, 0);
out_free:
free_bprm(bprm);
out_ret:
putname(filename);
return retval;
}
static int do_execve(struct filename *filename,
const char __user *const __user *__argv,
const char __user *const __user *__envp)
{
struct user_arg_ptr argv = { .ptr.native = __argv };
struct user_arg_ptr envp = { .ptr.native = __envp };
return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
}
static int do_execveat(int fd, struct filename *filename,
const char __user *const __user *__argv,
const char __user *const __user *__envp,
int flags)
{
struct user_arg_ptr argv = { .ptr.native = __argv };
struct user_arg_ptr envp = { .ptr.native = __envp };
return do_execveat_common(fd, filename, argv, envp, flags);
}
#ifdef CONFIG_COMPAT
static int compat_do_execve(struct filename *filename,
const compat_uptr_t __user *__argv,
const compat_uptr_t __user *__envp)
{
struct user_arg_ptr argv = {
.is_compat = true,
.ptr.compat = __argv,
};
struct user_arg_ptr envp = {
.is_compat = true,
.ptr.compat = __envp,
};
return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
}
static int compat_do_execveat(int fd, struct filename *filename,
const compat_uptr_t __user *__argv,
const compat_uptr_t __user *__envp,
int flags)
{
struct user_arg_ptr argv = {
.is_compat = true,
.ptr.compat = __argv,
};
struct user_arg_ptr envp = {
.is_compat = true,
.ptr.compat = __envp,
};
return do_execveat_common(fd, filename, argv, envp, flags);
}
#endif
void set_binfmt(struct linux_binfmt *new)
{
struct mm_struct *mm = current->mm;
if (mm->binfmt)
module_put(mm->binfmt->module);
mm->binfmt = new;
if (new)
__module_get(new->module);
}
EXPORT_SYMBOL(set_binfmt);
/*
* set_dumpable stores three-value SUID_DUMP_* into mm->flags.
*/
void set_dumpable(struct mm_struct *mm, int value)
{
if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
return;
set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value);
}
SYSCALL_DEFINE3(execve,
const char __user *, filename,
const char __user *const __user *, argv,
const char __user *const __user *, envp)
{
return do_execve(getname(filename), argv, envp);
}
SYSCALL_DEFINE5(execveat,
int, fd, const char __user *, filename,
const char __user *const __user *, argv,
const char __user *const __user *, envp,
int, flags)
{
return do_execveat(fd,
getname_uflags(filename, flags),
argv, envp, flags);
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
const compat_uptr_t __user *, argv,
const compat_uptr_t __user *, envp)
{
return compat_do_execve(getname(filename), argv, envp);
}
COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
const char __user *, filename,
const compat_uptr_t __user *, argv,
const compat_uptr_t __user *, envp,
int, flags)
{
return compat_do_execveat(fd,
getname_uflags(filename, flags),
argv, envp, flags);
}
#endif
#ifdef CONFIG_SYSCTL
static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!error)
validate_coredump_safety();
return error;
}
static struct ctl_table fs_exec_sysctls[] = {
{
.procname = "suid_dumpable",
.data = &suid_dumpable,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax_coredump,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
},
{ }
};
static int __init init_fs_exec_sysctls(void)
{
register_sysctl_init("fs", fs_exec_sysctls);
return 0;
}
fs_initcall(init_fs_exec_sysctls);
#endif /* CONFIG_SYSCTL */