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authorOleg Nesterov <oleg@redhat.com>2017-11-17 15:30:01 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-17 16:10:03 -0800
commit628c1bcba204052d19b686b5bac149a644cdb72e (patch)
treea1d325860abbe88b0561a31c4451f1527144380a /kernel
parenteecd7f4f5b9c2021dbde0a361b365f5970db52aa (diff)
kernel/signal.c: protect the traced SIGNAL_UNKILLABLE tasks from SIGKILL
The comment in sig_ignored() says "Tracers may want to know about even ignored signals" but SIGKILL can not be reported to debugger and it is just wrong to return 0 in this case: SIGKILL should only kill the SIGNAL_UNKILLABLE task if it comes from the parent ns. Change sig_ignored() to ignore ->ptrace if sig == SIGKILL and rely on sig_task_ignored(). SISGTOP coming from within the namespace is not really right too but at least debugger can intercept it, and we can't drop it here because this will break "gdb -p 1": ptrace_attach() won't work. Perhaps we will add another ->ptrace check later, we will see. Link: http://lkml.kernel.org/r/20171103184206.GB21036@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Kyle Huey <me@kylehuey.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/signal.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index aa1fb9f905db..be5913134742 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -94,13 +94,15 @@ static int sig_ignored(struct task_struct *t, int sig, bool force)
if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
return 0;
- if (!sig_task_ignored(t, sig, force))
- return 0;
-
/*
- * Tracers may want to know about even ignored signals.
+ * Tracers may want to know about even ignored signal unless it
+ * is SIGKILL which can't be reported anyway but can be ignored
+ * by SIGNAL_UNKILLABLE task.
*/
- return !t->ptrace;
+ if (t->ptrace && sig != SIGKILL)
+ return 0;
+
+ return sig_task_ignored(t, sig, force);
}
/*

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