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authorLinus Torvalds <torvalds@linux-foundation.org>2021-11-10 16:15:54 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-10 16:15:54 -0800
commit5147da902e0dd162c6254a61e4c57f21b60a9b1c (patch)
tree862b1147d858f56d24193d7e5921436019066b00 /kernel/signal.c
parenta41b74451b35f7a6529689760eb8c05241feecbc (diff)
parentf91140e4553408cacd326624cd50fc367725e04a (diff)
Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull exit cleanups from Eric Biederman: "While looking at some issues related to the exit path in the kernel I found several instances where the code is not using the existing abstractions properly. This set of changes introduces force_fatal_sig a way of sending a signal and not allowing it to be caught, and corrects the misuse of the existing abstractions that I found. A lot of the misuse of the existing abstractions are silly things such as doing something after calling a no return function, rolling BUG by hand, doing more work than necessary to terminate a kernel thread, or calling do_exit(SIGKILL) instead of calling force_sig(SIGKILL). In the review a deficiency in force_fatal_sig and force_sig_seccomp where ptrace or sigaction could prevent the delivery of the signal was found. I have added a change that adds SA_IMMUTABLE to change that makes it impossible to interrupt the delivery of those signals, and allows backporting to fix force_sig_seccomp And Arnd found an issue where a function passed to kthread_run had the wrong prototype, and after my cleanup was failing to build." * 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (23 commits) soc: ti: fix wkup_m3_rproc_boot_thread return type signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV) exit/r8188eu: Replace the macro thread_exit with a simple return 0 exit/rtl8712: Replace the macro thread_exit with a simple return 0 exit/rtl8723bs: Replace the macro thread_exit with a simple return 0 signal/x86: In emulate_vsyscall force a signal instead of calling do_exit signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails exit/syscall_user_dispatch: Send ordinary signals on failure signal: Implement force_fatal_sig exit/kthread: Have kernel threads return instead of calling do_exit signal/s390: Use force_sigsegv in default_trap_handler signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved. signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON signal/sparc: In setup_tsb_params convert open coded BUG into BUG signal/powerpc: On swapcontext failure force SIGSEGV signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT signal/sparc32: Remove unreachable do_exit in do_sparc_fault ...
Diffstat (limited to 'kernel/signal.c')
-rw-r--r--kernel/signal.c34
1 files changed, 24 insertions, 10 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 6f3476dc7873..7c4b7ae714d4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1323,6 +1323,7 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
blocked = sigismember(&t->blocked, sig);
if (blocked || ignored || sigdfl) {
action->sa.sa_handler = SIG_DFL;
+ action->sa.sa_flags |= SA_IMMUTABLE;
if (blocked) {
sigdelset(&t->blocked, sig);
recalc_sigpending_and_wake(t);
@@ -1649,6 +1650,19 @@ void force_sig(int sig)
}
EXPORT_SYMBOL(force_sig);
+void force_fatal_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, true);
+}
+
/*
* When things go south during signal handling, we
* will force a SIGSEGV. And if the signal that caused
@@ -1657,15 +1671,10 @@ EXPORT_SYMBOL(force_sig);
*/
void force_sigsegv(int sig)
{
- struct task_struct *p = current;
-
- if (sig == SIGSEGV) {
- unsigned long flags;
- spin_lock_irqsave(&p->sighand->siglock, flags);
- p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
- spin_unlock_irqrestore(&p->sighand->siglock, flags);
- }
- force_sig(SIGSEGV);
+ if (sig == SIGSEGV)
+ force_fatal_sig(SIGSEGV);
+ else
+ force_sig(SIGSEGV);
}
int force_sig_fault_to_task(int sig, int code, void __user *addr
@@ -2704,7 +2713,8 @@ relock:
if (!signr)
break; /* will return 0 */
- if (unlikely(current->ptrace) && signr != SIGKILL) {
+ if (unlikely(current->ptrace) && (signr != SIGKILL) &&
+ !(sighand->action[signr -1].sa.sa_flags & SA_IMMUTABLE)) {
signr = ptrace_signal(signr, &ksig->info);
if (!signr)
continue;
@@ -4054,6 +4064,10 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
k = &p->sighand->action[sig-1];
spin_lock_irq(&p->sighand->siglock);
+ if (k->sa.sa_flags & SA_IMMUTABLE) {
+ spin_unlock_irq(&p->sighand->siglock);
+ return -EINVAL;
+ }
if (oact)
*oact = *k;