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Merge branch 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Browse Source 
Pull exit-vs-signal handling fixes from Eric Biederman:
 "This is a small set of changes where debuggers were no longer able to
  intercept synchronous SIGTRAP and SIGSEGV, introduced by the exit
  cleanups.

  This is essentially the change you suggested with all of i's dotted
  and the t's crossed so that ptrace can intercept all of the cases it
  has been able to intercept the past, and all of the cases that made it
  to exit without giving ptrace a chance still don't give ptrace a
  chance"

* 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  signal: Replace force_fatal_sig with force_exit_sig when in doubt
  signal: Don't always set SA_IMMUTABLE for forced signals
This commit is contained in:
Linus Torvalds 2021-11-19 11:33:31 -08:00
commit 7af959b5d5
11 changed files with 42 additions and 19 deletions
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2
arch/m68k/kernel/traps.c
View File

@ -1145,7 +1145,7 @@ asmlinkage void set_esp0(unsigned long ssp)
*/
asmlinkage void fpsp040_die(void)
{
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
}
#ifdef CONFIG_M68KFPU_EMU

2
arch/powerpc/kernel/signal_32.c
View File

@ -1063,7 +1063,7 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
* We kill the task with a SIGSEGV in this situation.
*/
if (do_setcontext(new_ctx, regs, 0)) {
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
return -EFAULT;
}

4
arch/powerpc/kernel/signal_64.c
View File

@ -704,7 +704,7 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
*/
if (__get_user_sigset(&set, &new_ctx->uc_sigmask)) {
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
return -EFAULT;
}
set_current_blocked(&set);
@ -713,7 +713,7 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
return -EFAULT;
if (__unsafe_restore_sigcontext(current, NULL, 0, &new_ctx->uc_mcontext)) {
user_read_access_end();
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
return -EFAULT;
}
user_read_access_end();

2
arch/s390/kernel/traps.c
View File

@ -84,7 +84,7 @@ static void default_trap_handler(struct pt_regs *regs)
{
if (user_mode(regs)) {
report_user_fault(regs, SIGSEGV, 0);
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
} else
die(regs, "Unknown program exception");
}

4
arch/sparc/kernel/signal_32.c
View File

@ -244,7 +244,7 @@ static int setup_frame(struct ksignal *ksig, struct pt_regs *regs,
get_sigframe(ksig, regs, sigframe_size);
if (invalid_frame_pointer(sf, sigframe_size)) {
force_fatal_sig(SIGILL);
force_exit_sig(SIGILL);
return -EINVAL;
}
@ -336,7 +336,7 @@ static int setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs,
sf = (struct rt_signal_frame __user *)
get_sigframe(ksig, regs, sigframe_size);
if (invalid_frame_pointer(sf, sigframe_size)) {
force_fatal_sig(SIGILL);
force_exit_sig(SIGILL);
return -EINVAL;
}

2
arch/sparc/kernel/windows.c
View File

@ -122,7 +122,7 @@ void try_to_clear_window_buffer(struct pt_regs *regs, int who)
if ((sp & 7) ||
copy_to_user((char __user *) sp, &tp->reg_window[window],
sizeof(struct reg_window32))) {
force_fatal_sig(SIGILL);
force_exit_sig(SIGILL);
return;
}
}

2
arch/x86/entry/vsyscall/vsyscall_64.c
View File

@ -226,7 +226,7 @@ bool emulate_vsyscall(unsigned long error_code,
if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
warn_bad_vsyscall(KERN_DEBUG, regs,
"seccomp tried to change syscall nr or ip");
force_fatal_sig(SIGSYS);
force_exit_sig(SIGSYS);
return true;
}
regs->orig_ax = -1;

2
arch/x86/kernel/vm86_32.c
View File

@ -160,7 +160,7 @@ Efault_end:
user_access_end();
Efault:
pr_alert("could not access userspace vm86 info\n");
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
goto exit_vm86;
}

1
include/linux/sched/signal.h
View File

@ -352,6 +352,7 @@ extern __must_check bool do_notify_parent(struct task_struct *, int);
extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
extern void force_sig(int);
extern void force_fatal_sig(int);
extern void force_exit_sig(int);
extern int send_sig(int, struct task_struct *, int);
extern int zap_other_threads(struct task_struct *p);
extern struct sigqueue *sigqueue_alloc(void);

4
kernel/entry/syscall_user_dispatch.c
View File

@ -48,7 +48,7 @@ bool syscall_user_dispatch(struct pt_regs *regs)
* the selector is loaded by userspace.
*/
if (unlikely(__get_user(state, sd->selector))) {
force_fatal_sig(SIGSEGV);
force_exit_sig(SIGSEGV);
return true;
}
@ -56,7 +56,7 @@ bool syscall_user_dispatch(struct pt_regs *regs)
return false;
if (state != SYSCALL_DISPATCH_FILTER_BLOCK) {
force_fatal_sig(SIGSYS);
force_exit_sig(SIGSYS);
return true;
}
}

36
kernel/signal.c
View File

@ -1298,6 +1298,12 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
return ret;
}
enum sig_handler {
HANDLER_CURRENT, /* If reachable use the current handler */
HANDLER_SIG_DFL, /* Always use SIG_DFL handler semantics */
HANDLER_EXIT, /* Only visible as the process exit code */
};
/*
* Force a signal that the process can't ignore: if necessary
* we unblock the signal and change any SIG_IGN to SIG_DFL.
@ -1310,7 +1316,8 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
* that is why we also clear SIGNAL_UNKILLABLE.
*/
static int
force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool sigdfl)
force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t,
enum sig_handler handler)
{
unsigned long int flags;
int ret, blocked, ignored;
@ -1321,9 +1328,10 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
action = &t->sighand->action[sig-1];
ignored = action->sa.sa_handler == SIG_IGN;
blocked = sigismember(&t->blocked, sig);
if (blocked || ignored || sigdfl) {
if (blocked || ignored || (handler != HANDLER_CURRENT)) {
action->sa.sa_handler = SIG_DFL;
action->sa.sa_flags |= SA_IMMUTABLE;
if (handler == HANDLER_EXIT)
action->sa.sa_flags |= SA_IMMUTABLE;
if (blocked) {
sigdelset(&t->blocked, sig);
recalc_sigpending_and_wake(t);
@ -1343,7 +1351,7 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
int force_sig_info(struct kernel_siginfo *info)
{
return force_sig_info_to_task(info, current, false);
return force_sig_info_to_task(info, current, HANDLER_CURRENT);
}
/*
@ -1660,7 +1668,20 @@ void force_fatal_sig(int sig)
info.si_code = SI_KERNEL;
info.si_pid = 0;
info.si_uid = 0;
force_sig_info_to_task(&info, current, true);
force_sig_info_to_task(&info, current, HANDLER_SIG_DFL);
}
void force_exit_sig(int sig)
{
struct kernel_siginfo info;
clear_siginfo(&info);
info.si_signo = sig;
info.si_errno = 0;
info.si_code = SI_KERNEL;
info.si_pid = 0;
info.si_uid = 0;
force_sig_info_to_task(&info, current, HANDLER_EXIT);
}
/*
@ -1693,7 +1714,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr
info.si_flags = flags;
info.si_isr = isr;
#endif
return force_sig_info_to_task(&info, t, false);
return force_sig_info_to_task(&info, t, HANDLER_CURRENT);
}
int force_sig_fault(int sig, int code, void __user *addr
@ -1813,7 +1834,8 @@ int force_sig_seccomp(int syscall, int reason, bool force_coredump)
info.si_errno = reason;
info.si_arch = syscall_get_arch(current);
info.si_syscall = syscall;
return force_sig_info_to_task(&info, current, force_coredump);
return force_sig_info_to_task(&info, current,
force_coredump ? HANDLER_EXIT : HANDLER_CURRENT);
}
/* For the crazy architectures that include trap information in