From: ebiederm@xmission.com (Eric W. Biederman)
To: Eric Biggers <ebiggers@kernel.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Bug (since v4.20): integer underflow in known_siginfo_layout() when sig=0
Date: Sat, 12 Jan 2019 11:43:01 -0600 [thread overview]
Message-ID: <87a7k5ai1m.fsf@xmission.com> (raw)
In-Reply-To: <20190112005305.GB77447@gmail.com> (Eric Biggers's message of "Fri, 11 Jan 2019 16:53:06 -0800")
Eric Biggers <ebiggers@kernel.org> writes:
> Hi Eric,
>
> The following commit, which went into v4.20, introduced undefined behavior when
> sys_rt_sigqueueinfo() is called with sig=0:
Ouch. Good catch.
It looks like the fix is just to do:
diff --git a/include/linux/signal.h b/include/linux/signal.h
index f428e86f4800..b5d99482d3fe 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -388,7 +388,7 @@ extern bool unhandled_signal(struct task_struct *tsk, int sig);
#endif
#define siginmask(sig, mask) \
- ((sig) < SIGRTMIN && (rt_sigmask(sig) & (mask)))
+ ((sig) > 0 && (sig) < SIGRTMIN && (rt_sigmask(sig) & (mask)))
#define SIG_KERNEL_ONLY_MASK (\
rt_sigmask(SIGKILL) | rt_sigmask(SIGSTOP))
As gcc is smart enough to combine those two range tests into a single
comparison. That will ensure the undefined behavior does not byte
anyone else.
I will see about whipping up a proper patch.
Eric
prev parent reply other threads:[~2019-01-12 17:43 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-12 0:53 Bug (since v4.20): integer underflow in known_siginfo_layout() when sig=0 Eric Biggers
2019-01-12 17:43 ` Eric W. Biederman [this message]
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