maccess: always use strict semantics for probe_kernel_read

Except for historical confusion in the kprobes/uprobes and bpf tracers,
which has been fixed now, there is no good reason to ever allow user
memory accesses from probe_kernel_read.  Switch probe_kernel_read to only
read from kernel memory.

[akpm@linux-foundation.org: update it for "mm, dump_page(): do not crash with invalid mapping pointer"]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-17-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2020-06-08 21:34:50 -07:00 committed by Linus Torvalds
parent 7676fbf21b
commit 98a23609b1
8 changed files with 19 additions and 54 deletions

View File

@ -57,7 +57,7 @@ void * memcpy(void * dst,const void *src, size_t count)
EXPORT_SYMBOL(raw_copy_in_user);
EXPORT_SYMBOL(memcpy);
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
if ((unsigned long)unsafe_src < PAGE_SIZE)
return false;

View File

@ -7,7 +7,7 @@
#include <linux/kernel.h>
#include <os.h>
bool probe_kernel_read_allowed(const void *src, size_t size, bool strict)
bool probe_kernel_read_allowed(const void *src, size_t size)
{
void *psrc = (void *)rounddown((unsigned long)src, PAGE_SIZE);

View File

@ -9,13 +9,10 @@ static __always_inline u64 canonical_address(u64 vaddr, u8 vaddr_bits)
return ((s64)vaddr << (64 - vaddr_bits)) >> (64 - vaddr_bits);
}
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
unsigned long vaddr = (unsigned long)unsafe_src;
if (!strict)
return true;
/*
* Range covering the highest possible canonical userspace address
* as well as non-canonical address range. For the canonical range
@ -25,10 +22,8 @@ bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
canonical_address(vaddr, boot_cpu_data.x86_virt_bits) == vaddr;
}
#else
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size, bool strict)
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
if (!strict)
return true;
return (unsigned long)unsafe_src >= TASK_SIZE_MAX;
}
#endif

View File

@ -301,11 +301,9 @@ copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
return 0;
}
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size,
bool strict);
bool probe_kernel_read_allowed(const void *unsafe_src, size_t size);
extern long probe_kernel_read(void *dst, const void *src, size_t size);
extern long probe_kernel_read_strict(void *dst, const void *src, size_t size);
extern long probe_user_read(void *dst, const void __user *src, size_t size);
extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);

View File

@ -196,7 +196,7 @@ bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
if (unlikely(ret < 0))
goto fail;
ret = probe_kernel_read_strict(dst, unsafe_ptr, size);
ret = probe_kernel_read(dst, unsafe_ptr, size);
if (unlikely(ret < 0))
goto fail;
return ret;

View File

@ -1222,7 +1222,7 @@ fetch_store_strlen(unsigned long addr)
#endif
do {
ret = probe_kernel_read_strict(&c, (u8 *)addr + len, 1);
ret = probe_kernel_read(&c, (u8 *)addr + len, 1);
len++;
} while (c && ret == 0 && len < MAX_STRING_SIZE);
@ -1300,7 +1300,7 @@ probe_mem_read(void *dest, void *src, size_t size)
if ((unsigned long)src < TASK_SIZE)
return probe_mem_read_user(dest, src, size);
#endif
return probe_kernel_read_strict(dest, src, size);
return probe_kernel_read(dest, src, size);
}
/* Note that we don't verify it, since the code does not come from user space */

View File

@ -120,9 +120,9 @@ void __dump_page(struct page *page, const char *reason)
* mapping can be invalid pointer and we don't want to crash
* accessing it, so probe everything depending on it carefully
*/
if (probe_kernel_read_strict(&host, &mapping->host,
sizeof(struct inode *)) ||
probe_kernel_read_strict(&a_ops, &mapping->a_ops,
if (probe_kernel_read(&host, &mapping->host,
sizeof(struct inode *)) ||
probe_kernel_read(&a_ops, &mapping->a_ops,
sizeof(struct address_space_operations *))) {
pr_warn("failed to read mapping->host or a_ops, mapping not a valid kernel address?\n");
goto out_mapping;
@ -133,7 +133,7 @@ void __dump_page(struct page *page, const char *reason)
goto out_mapping;
}
if (probe_kernel_read_strict(&dentry_first,
if (probe_kernel_read(&dentry_first,
&host->i_dentry.first, sizeof(struct hlist_node *))) {
pr_warn("mapping->a_ops:%ps with invalid mapping->host inode address %px\n",
a_ops, host);
@ -146,7 +146,7 @@ void __dump_page(struct page *page, const char *reason)
}
dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias);
if (probe_kernel_read_strict(&dentry, dentry_ptr,
if (probe_kernel_read(&dentry, dentry_ptr,
sizeof(struct dentry))) {
pr_warn("mapping->aops:%ps with invalid mapping->host->i_dentry.first %px\n",
a_ops, dentry_ptr);

View File

@ -6,36 +6,13 @@
#include <linux/mm.h>
#include <linux/uaccess.h>
static long __probe_kernel_read(void *dst, const void *src, size_t size,
bool strict);
bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size,
bool strict)
bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size)
{
return true;
}
/**
* probe_kernel_read(): safely attempt to read from any location
* @dst: pointer to the buffer that shall take the data
* @src: address to read from
* @size: size of the data chunk
*
* Same as probe_kernel_read_strict() except that for architectures with
* not fully separated user and kernel address spaces this function also works
* for user address tanges.
*
* DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
* separate kernel and user address spaces, and also a bad idea otherwise.
*/
long probe_kernel_read(void *dst, const void *src, size_t size)
{
return __probe_kernel_read(dst, src, size, false);
}
EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
* probe_kernel_read_strict(): safely attempt to read from kernel-space
* probe_kernel_read(): safely attempt to read from kernel-space
* @dst: pointer to the buffer that shall take the data
* @src: address to read from
* @size: size of the data chunk
@ -48,18 +25,12 @@ EXPORT_SYMBOL_GPL(probe_kernel_read);
* probe_kernel_read() suitable for use within regions where the caller
* already holds mmap_lock, or other locks which nest inside mmap_lock.
*/
long probe_kernel_read_strict(void *dst, const void *src, size_t size)
{
return __probe_kernel_read(dst, src, size, true);
}
static long __probe_kernel_read(void *dst, const void *src, size_t size,
bool strict)
long probe_kernel_read(void *dst, const void *src, size_t size)
{
long ret;
mm_segment_t old_fs = get_fs();
if (!probe_kernel_read_allowed(src, size, strict))
if (!probe_kernel_read_allowed(src, size))
return -EFAULT;
set_fs(KERNEL_DS);
@ -73,6 +44,7 @@ static long __probe_kernel_read(void *dst, const void *src, size_t size,
return -EFAULT;
return 0;
}
EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
* probe_user_read(): safely attempt to read from a user-space location
@ -181,7 +153,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
if (unlikely(count <= 0))
return 0;
if (!probe_kernel_read_allowed(unsafe_addr, count, true))
if (!probe_kernel_read_allowed(unsafe_addr, count))
return -EFAULT;
set_fs(KERNEL_DS);