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Message-ID: <20140619044835.GM179@brightrain.aerifal.cx>
Date: Thu, 19 Jun 2014 00:48:35 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Re: uninitialized memory access in memmem()
On Wed, Jun 18, 2014 at 11:56:20PM -0400, Rich Felker wrote:
> On Thu, Jun 19, 2014 at 01:43:50AM +0000, Clément Vasseur wrote:
> > On 2014-06-19, Rich Felker <dalias@...c.org> wrote:
> > > On Wed, Jun 18, 2014 at 06:20:33PM +0000, Clément Vasseur wrote:
> > >> Hello,
> > >>
> > >> I found a case where memmem() returns 0 where it should not:
> > >>
> > >> $ cat test-memmem.c
> > >> #define _GNU_SOURCE
> > >> #include <string.h>
> > >> #include <assert.h>
> > >>
> > >> #define DATA 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
> > >>
> > >> int main(void)
> > >> {
> > >> const unsigned char haystack[] = { DATA };
> > >> const unsigned char needle[] = { DATA };
> > >> assert(memmem(haystack, sizeof haystack, needle, sizeof needle));
> > >> }
> > >>
> > >> $ musl-gcc test-memmem.c && ./a.out
> > >> Assertion failed: memmem(haystack, sizeof haystack, needle, sizeof needle) (test-memmem.c: main: 11)
> > >> Aborted
> > >>
> > >> Valgrind says a conditional jump or move depends on uninitalized value
> > >> in twoway_memmem(). The code is quite complicated so I have not tried to
> > >> track it down any further.
> > >
> > > Can you provide more details? musl version? gcc version? arch? I can't
> > > reproduce this error in master with gcc 4.7.3/i386.
> >
> > I use master (7c73cac) with gcc 4.6.1/x86_64.
> >
> > I have another pattern which fails with gcc 4.8.3/arm. Looks like you
> > might reproduce this one on your 32-bit arch:
> >
> > #define DATA 0x50, 0x17, 0x8a, 0xf3, 0x55, 0x67, 0x58, 0xdf
>
> Are you sure you're actually using musl master? The file that matters
> is /lib/ld-musl-$ARCH.so.1. If it's a symlink to an old musl you have
> lying around somewhere, then that's the version you're really using. I
> was able to reproduce this with musl 1.0.0 and it's simply the bug
> fixed in commit 476cd1d96560aaf7f210319597556e7fbcd60469.
Sorry, I was wrong. This appeared to be the case at first, but I was
able to reproduce the bug with some more work -- it's hard to
reproduce because, like valgrind reported, it's an invalid read.
Fixed in commit cef0f289f666b6c963bfd11537a6d80916ff889e.
Rich
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