diff options
author | Oleg Nesterov <oleg@redhat.com> | 2009-04-02 19:58:02 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-02 22:04:58 -0400 |
commit | f008faff0e2777c8b3fe853891b774ca465938d8 (patch) | |
tree | d2f325995473a33652f7f7ead71e63d5298fbd01 /kernel | |
parent | 43918f2bf4806675943416d539d9d5e4d585ebff (diff) |
signals: protect init from unwanted signals more
(This is a modified version of the patch submitted by Oleg Nesterov
http://lkml.org/lkml/2008/11/18/249 and tries to address comments that
came up in that discussion)
init ignores the SIG_DFL signals but we queue them anyway, including
SIGKILL. This is mostly OK, the signal will be dropped silently when
dequeued, but the pending SIGKILL has 2 bad implications:
- it implies fatal_signal_pending(), so we confuse things
like wait_for_completion_killable/lock_page_killable.
- for the sub-namespace inits, the pending SIGKILL can
mask (legacy_queue) the subsequent SIGKILL from the
parent namespace which must kill cinit reliably.
(preparation, cinits don't have SIGNAL_UNKILLABLE yet)
The patch can't help when init is ptraced, but ptracing of init is not
"safe" anyway.
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
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.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 92a1ab004498..8bf7a40e5c71 100644 --- a/kernel/signal.c +++ b/kernel/signal.c | |||
@@ -55,10 +55,21 @@ static int sig_handler_ignored(void __user *handler, int sig) | |||
55 | (handler == SIG_DFL && sig_kernel_ignore(sig)); | 55 | (handler == SIG_DFL && sig_kernel_ignore(sig)); |
56 | } | 56 | } |
57 | 57 | ||
58 | static int sig_ignored(struct task_struct *t, int sig) | 58 | static int sig_task_ignored(struct task_struct *t, int sig) |
59 | { | 59 | { |
60 | void __user *handler; | 60 | void __user *handler; |
61 | 61 | ||
62 | handler = sig_handler(t, sig); | ||
63 | |||
64 | if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && | ||
65 | handler == SIG_DFL) | ||
66 | return 1; | ||
67 | |||
68 | return sig_handler_ignored(handler, sig); | ||
69 | } | ||
70 | |||
71 | static int sig_ignored(struct task_struct *t, int sig) | ||
72 | { | ||
62 | /* | 73 | /* |
63 | * Blocked signals are never ignored, since the | 74 | * Blocked signals are never ignored, since the |
64 | * signal handler may change by the time it is | 75 | * signal handler may change by the time it is |
@@ -67,8 +78,7 @@ static int sig_ignored(struct task_struct *t, int sig) | |||
67 | if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig)) | 78 | if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig)) |
68 | return 0; | 79 | return 0; |
69 | 80 | ||
70 | handler = sig_handler(t, sig); | 81 | if (!sig_task_ignored(t, sig)) |
71 | if (!sig_handler_ignored(handler, sig)) | ||
72 | return 0; | 82 | return 0; |
73 | 83 | ||
74 | /* | 84 | /* |