The patch titled
Subject: kernel/signal.c: protect the traced SIGNAL_UNKILLABLE tasks from SIGKILL
has been added to the -mm tree. Its filename is
protect-the-traced-signal_unkillable-tasks-from-sigkill.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/protect-the-traced-signal_unkillable-tasks-from-sigkill.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/protect-the-traced-signal_unkillable-tasks-from-sigkill.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Tested-by: Kyle Huey <me@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/signal.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff -puN kernel/signal.c~protect-the-traced-signal_unkillable-tasks-from-sigkill kernel/signal.c
--- a/kernel/signal.c~protect-the-traced-signal_unkillable-tasks-from-sigkill
+++ a/kernel/signal.c
@@ -94,13 +94,15 @@ static int sig_ignored(struct task_struc
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);
}
/*
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
protect-the-traced-signal_unkillable-tasks-from-sigkill.patch
protect-the-signal_unkillable-tasks-from-sig_kernel_only-signals.patch
remove-the-no-longer-needed-signal_unkillable-check-in-complete_signal.patch
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