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Date: Wed, 28 Jul 2021 15:36:28 -0400
From: Rich Felker <dalias@...c.org>
To: Jasper Hugunin <jasper@...unin.net>
Cc: musl@...ts.openwall.com
Subject: Re: Bug in src/signal/block.c
On Wed, Jul 28, 2021 at 11:53:41AM -0400, Rich Felker wrote:
> On Wed, Jul 28, 2021 at 08:00:00AM -0700, Jasper Hugunin wrote:
> > Hello,
> >
> > In musl, as far as I can tell, `_NSIG` is always defined as either 65, or
> > 128 (for all three MIPS architectures) at the bottom of
> > `${arch}/bits/signal.h`. Meanwhile, in `src/signal/block.c`, there is a
> > test `#if ULONG_MAX == 0xffffffff && _NSIG == 129`, which will never
> > succeed since _NSIG will be 128 instead of 129. This seems likely to be
> > left over from Commit: fix _NSIG and SIGRTMAX on mips
> > <https://git.musl-libc.org/cgit/musl/commit/arch?id=7c440977db9444d7e6b1c3dcb1fdf4ee49ca4158>
> > ..
> >
> > I have not demonstrated the bug, I found it by inspection of the source. My
> > guess is that this bug causes __block_all_sigs to fail to block high real
> > time signals on MIPS. At best, however, this test seems to be dead code.
> >
> > (I am not subscribed to the mailing list; please cc me directly on any
> > responses I need to see.)
> > My apologies if I have misunderstood the situation.
>
> Thanks! This is a real bug that will prevent signal blocking from
> working correctly on mips, resulting in application code being able to
> run in contexts where it is unsafe for that to happen if the
> application installs signal handlers on high signal numbers.
Does the attached patch look ok?
Rich
View attachment "sigblock-mips.diff" of type "text/plain" (434 bytes)
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