From: ebiederm@xmission.com (Eric W. Biederman)
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, "Kyle Huey" <me@kylehuey.com>,
"Jens Axboe" <axboe@kernel.dk>,
"Peter Zijlstra" <peterz@infradead.org>,
"Marco Elver" <elver@google.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Peter Collingbourne" <pcc@google.com>,
"Alexey Gladkov" <legion@kernel.org>,
"Robert O'Callahan" <rocallahan@gmail.com>,
"Marko Mäkelä" <marko.makela@mariadb.com>,
linux-api@vger.kernel.org, "Al Viro" <viro@zeniv.linux.org.uk>,
"Linus Torvalds" <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/3] signal: In get_signal test for signal_group_exit every time through the loop
Date: Wed, 17 Nov 2021 10:31:20 -0600 [thread overview]
Message-ID: <877dd6bv6v.fsf@email.froward.int.ebiederm.org> (raw)
In-Reply-To: <202111161022.7B5720B@keescook> (Kees Cook's message of "Tue, 16 Nov 2021 10:23:48 -0800")
Kees Cook <keescook@chromium.org> writes:
> On Mon, Nov 15, 2021 at 11:32:50PM -0600, Eric W. Biederman wrote:
>>
>> Recently while investigating a problem with rr and signals I noticed
>> that siglock is dropped in ptrace_signal and get_signal does not jump
>> to relock.
>>
>> Looking farther to see if the problem is anywhere else I see that
>> do_signal_stop also returns if signal_group_exit is true. I believe
>> that test can now never be true, but it is a bit hard to trace
>> through and be certain.
>>
>> Testing signal_group_exit is not expensive, so move the test for
>> signal_group_exit into the for loop inside of get_signal to ensure
>> the test is never skipped improperly.
>
> Seems reasonable.
>
>>
>> This has been a potential since I added the test for signal_group_exit
>
> nit: missing word after "potential"? "bug", "problem"?
Yes. Potential problem. I will update the comment.
>> was added.
>>
>> Fixes: 35634ffa1751 ("signal: Always notice exiting tasks")
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
>> ---
>> kernel/signal.c | 20 ++++++++++----------
>> 1 file changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/kernel/signal.c b/kernel/signal.c
>> index 7c4b7ae714d4..986fa69c15c5 100644
>> --- a/kernel/signal.c
>> +++ b/kernel/signal.c
>> @@ -2662,19 +2662,19 @@ bool get_signal(struct ksignal *ksig)
>> goto relock;
>> }
>>
>> - /* Has this task already been marked for death? */
>> - if (signal_group_exit(signal)) {
>> - ksig->info.si_signo = signr = SIGKILL;
>> - sigdelset(¤t->pending.signal, SIGKILL);
>> - trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
>> - &sighand->action[SIGKILL - 1]);
>> - recalc_sigpending();
>> - goto fatal;
>> - }
>> -
>> for (;;) {
>> struct k_sigaction *ka;
>>
>> + /* Has this task already been marked for death? */
>> + if (signal_group_exit(signal)) {
>> + ksig->info.si_signo = signr = SIGKILL;
>> + sigdelset(¤t->pending.signal, SIGKILL);
>> + trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
>> + &sighand->action[SIGKILL - 1]);
>> + recalc_sigpending();
>> + goto fatal;
>> + }
>> +
>> if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
>> do_signal_stop(0))
>> goto relock;
>> --
>> 2.20.1
>>
next prev parent reply other threads:[~2021-11-17 16:31 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 3:41 [PATCH] signal: SIGKILL can cause signal effects to appear at PTRACE_EVENT_EXIT without tracer notification Kyle Huey
2021-11-01 3:41 ` [PATCH 1/2] signal: factor out SIGKILL generation in get_signal Kyle Huey
2021-11-01 3:41 ` [PATCH 2/2] signal: after notifying a ptracer of a signal, recheck for pending SIGKILLs Kyle Huey
2021-11-02 14:08 ` [PATCH] signal: SIGKILL can cause signal effects to appear at PTRACE_EVENT_EXIT without tracer notification Eric W. Biederman
2021-11-02 16:01 ` Kyle Huey
2021-11-02 18:06 ` Eric W. Biederman
2021-11-02 19:09 ` Kyle Huey
2021-11-08 23:58 ` Kyle Huey
2021-11-14 17:19 ` Eric W. Biederman
2021-11-16 5:29 ` [PATCH 0/3] signal: requeuing undeliverable signals Eric W. Biederman
2021-11-16 5:32 ` [PATCH 1/3] signal: In get_signal test for signal_group_exit every time through the loop Eric W. Biederman
2021-11-16 18:23 ` Kees Cook
2021-11-17 16:31 ` Eric W. Biederman [this message]
2021-11-16 5:33 ` [PATCH 2/3] signal: Requeue signals in the appropriate queue Eric W. Biederman
2021-11-16 18:30 ` Kees Cook
2021-11-17 16:42 ` Eric W. Biederman
2021-11-16 5:34 ` [PATCH 3/3] signal: Requeue ptrace signals Eric W. Biederman
2021-11-16 18:31 ` Kees Cook
2021-11-17 16:44 ` Eric W. Biederman
2021-11-17 16:24 ` [PATCH 0/3] signal: requeuing undeliverable signals Kyle Huey
2021-11-17 16:51 ` Eric W. Biederman
2021-11-18 6:12 ` Marko Mäkelä
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