From: "Narayanan Iyer" <nars@yottadb.com>
To: "'Noah Goldstein'" <goldstein.w.n@gmail.com>
Cc: <libc-alpha@sourceware.org>
Subject: RE: Bug 29863 - Segmentation fault in memcmp-sse2.S if memory contents can concurrently change
Date: Tue, 13 Dec 2022 14:13:22 -0500 [thread overview]
Message-ID: <0b2901d90f26$f82b4720$e881d560$@yottadb.com> (raw)
In-Reply-To: <CAFUsyfKXSTCkLsAVGb+8T0nVPZPq_UykNAWNyCuBGTEQXdbJfw@mail.gmail.com>
Noah,
Thank you for acknowledging that it is a bug.
In case it helps, I found in our testing cluster, that a system which uses sysdeps/x86_64/multiarch/memcmp-sse2.S has the bug whereas a system that uses sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S does not have the bug.
So it is possible, the issue is only in the sse2 version.
Thanks,
Narayanan.
-----Original Message-----
From: Noah Goldstein [mailto:goldstein.w.n@gmail.com]
Sent: Tuesday, December 13, 2022 2:08 PM
To: Narayanan Iyer <nars@yottadb.com>
Cc: libc-alpha@sourceware.org
Subject: Re: Bug 29863 - Segmentation fault in memcmp-sse2.S if memory contents can concurrently change
On Tue, Dec 13, 2022 at 10:20 AM Narayanan Iyer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Hi,
>
> I had created a glibc bug report at https://sourceware.org/bugzilla/show_bug.cgi?id=29863
>
> And have included the title of that report in the email subject as well.
>
> It has been a week since I created the issue and I did not hear anything back. I believe this is a regression in glibc 2.36 and have provided enough information in the bug report (along with the commit that caused the regression).
>
> Given the upcoming glibc 2.37 release, I was asked (by Carlos O'Donell <carlos@redhat.com>) to raise it on this mailing list to get the attention of the glibc developers.
>
> I am hoping one of you could take a quick look at the bug report and see if it is worth fixing it in time for glibc 2.37.
>
> Thanks,
> Narayanan.
>
>
The fix:
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/x86_64/multiarch/memcmp-sse2.S;h=afd450d0206d6633da9fbc4607a7fa6aeb4e137c;hb=HEAD#l46
```
-# define SIZE_OFFSET (CHAR_PER_VEC * 2)
+# define SIZE_OFFSET 0
```
Is this something we have to support? I believe other functions /
implementations
of memcmp will suffer from a similar bug.
next prev parent reply other threads:[~2022-12-13 19:13 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-13 18:20 Narayanan Iyer
2022-12-13 18:31 ` Andrew Pinski
2022-12-13 18:39 ` Narayanan Iyer
2022-12-13 18:39 ` Cristian Rodríguez
2022-12-13 19:08 ` Noah Goldstein
2022-12-13 19:13 ` Narayanan Iyer [this message]
2022-12-13 19:25 ` Noah Goldstein
2022-12-13 20:56 ` Zack Weinberg
2022-12-13 23:29 ` Carlos O'Donell
2022-12-14 2:28 ` Zack Weinberg
2022-12-14 4:16 ` Carlos O'Donell
2022-12-14 14:16 ` Zack Weinberg
2022-12-14 17:36 ` Paolo Bonzini
2022-12-29 7:09 ` Zack Weinberg
2022-12-29 19:32 ` “Undefined behavior” considered harmful (was Re: Bug 29863 - Segmentation fault in memcmp-sse2.S…) Zack Weinberg
2022-12-29 22:20 ` Andreas Schwab
2022-12-30 13:28 ` Florian Weimer
2022-12-30 15:09 ` Florian Weimer
2022-12-13 22:52 ` Bug 29863 - Segmentation fault vs invalid results, memory models, and control/data dependencies Carlos O'Donell
2022-12-14 12:03 ` Florian Weimer
2022-12-13 21:20 ` Bug 29863 - Segmentation fault in memcmp-sse2.S if memory contents can concurrently change Florian Weimer
2022-12-13 22:59 ` Noah Goldstein
2022-12-14 12:06 ` Florian Weimer
[not found] <PAWPR08MB89825887E12FF900540365F483E09@PAWPR08MB8982.eurprd08.prod.outlook.com>
[not found] ` <PAWPR08MB898260DA844D695EA70ED3E483E09@PAWPR08MB8982.eurprd08.prod.outlook.com>
2022-12-14 21:56 ` Wilco Dijkstra
2022-12-29 7:21 ` Zack Weinberg
2022-12-29 20:02 ` Alejandro Colomar
2022-12-30 18:02 ` Joseph Myers
2023-03-20 15:40 ` Zack Weinberg
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