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SubjectRe: 2.6.x signal handler bug
On Mon, 28 Jun 2004, Andries Brouwer wrote:

> On Sat, Jun 26, 2004 at 09:05:34AM -0700, Davide Libenzi wrote:
>
> > You're receiving a SIGSEGV while SIGSEGV is blocked (force_sig_info). The
> > force_sig_info call wants to send a signal that the task can't refuse
> > (kinda The GodFather offers ;). The kernel will noticed this and will
> > restore the handler to SIG_DFL.
>
> Yes.
>
> So checking whether this is POSIX conforming:
>
> - Blocking a signal in its signal handler is explicitly allowed.
> (signal(3p))
> - It is unspecified what longjmp() does with the signal mask.
> (longjmp(3p))
> - The SIGSEGV that occurs during a stack overflow is of the GodFather kind.
> (getrlimit(3p))
> - If SIGSEGV is generated while blocked, the result is undefined
> (sigprocmask(3p))
>
> So, maybe the restoring to SIG_DFL was not required, but it doesnt seem
> incorrect either. It may be a bit surprising.

I think so. Maybe the attached patch?



- Davide




--- a/kernel/signal.c 2004-06-27 15:42:26.000000000 -0700
+++ b/kernel/signal.c 2004-06-27 15:43:28.000000000 -0700
@@ -820,8 +820,9 @@
int ret;

spin_lock_irqsave(&t->sighand->siglock, flags);
- if (sigismember(&t->blocked, sig) || t->sighand->action[sig-1].sa.sa_handler == SIG_IGN) {
- t->sighand->action[sig-1].sa.sa_handler = SIG_DFL;
+ if (sigismember(&t->blocked, sig)) {
+ if (t->sighand->action[sig-1].sa.sa_handler == SIG_IGN)
+ t->sighand->action[sig-1].sa.sa_handler = SIG_DFL;
sigdelset(&t->blocked, sig);
recalc_sigpending_tsk(t);
}
-
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