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Bug#1021426: bullseye-pu: package glibc/2.31-13+deb11u5
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Aurelien Jarno
Oct 8, 2022, 5:40:03 AM10/8/22
to
Package: release.debian.org
Severity: normal
Tags: bullseye
User: release.d...@packages.debian.org
Usertags: pu
X-Debbugs-Cc: debian...@lists.debian.org
[ Reason ]
The glibc/2.31-13+deb11u4 update introduced a regression (bug #1019855)
on some early Intel Haswell processors which expose the AVX2
instructions, but lack the BMI2 instructions. On such systems the memchr
and strlen related functions fails with SIGILL, rendering them unusable.
The issue is that some of the backported commits to fix the overflow
bugs in the AVX2 implementation of wmemchr and wcslen that went in the
upstream 2.31 branch, started to use BMI2 instructions in addition to
the AVX2 instructions, without checking for the availability of those
instructions. This was done in another commit that hasn't been
backported.
It happens that a microcode update for the affected CPUs (either through
the BIOS/firmware or from a package) fixes this, so it went barely
noticed up to now, especially given other distributions usually install
firmware updates by default.
[ Impact ]
While the number of affected systems is probably small, this bug makes
them unusable.
[ Tests ]
This has been tested, by replacing all BMI2 instructions in the glibc
source code by the UD2 x86 instruction. This triggered the same issue
than the reported one in bug#1019855. Then the detection of BMI2
instructions has been disabled in the source code, and the resulting
glibc was working as expected without generating SIGILL.
[ Risks ]
The change is intentionally minimal, smaller than the upstream one, and
only targets the runtime execution. Some tests of the testsuite will
still fail on affected systems. This part can be fixed later in a point
release. This way the risks should be minimal.
[ Checklist ]
[x] *all* changes are documented in the d/changelog
[x] I reviewed all changes and I approve them
[x] attach debdiff against the package in (old)stable
[x] the issue is verified as fixed in unstable
[ Changes ]
The change is very simple and consists in adding a check for BMI2
instructions in the ifunc selector that selects the AVX2 optimized code.
[ Other info ]
Given the severity of the bug, it might be a good idea to release it
through stable-updates.
Severity: normal
Tags: bullseye
User: release.d...@packages.debian.org
Usertags: pu
X-Debbugs-Cc: debian...@lists.debian.org
[ Reason ]
The glibc/2.31-13+deb11u4 update introduced a regression (bug #1019855)
on some early Intel Haswell processors which expose the AVX2
instructions, but lack the BMI2 instructions. On such systems the memchr
and strlen related functions fails with SIGILL, rendering them unusable.
The issue is that some of the backported commits to fix the overflow
bugs in the AVX2 implementation of wmemchr and wcslen that went in the
upstream 2.31 branch, started to use BMI2 instructions in addition to
the AVX2 instructions, without checking for the availability of those
instructions. This was done in another commit that hasn't been
backported.
It happens that a microcode update for the affected CPUs (either through
the BIOS/firmware or from a package) fixes this, so it went barely
noticed up to now, especially given other distributions usually install
firmware updates by default.
[ Impact ]
While the number of affected systems is probably small, this bug makes
them unusable.
[ Tests ]
This has been tested, by replacing all BMI2 instructions in the glibc
source code by the UD2 x86 instruction. This triggered the same issue
than the reported one in bug#1019855. Then the detection of BMI2
instructions has been disabled in the source code, and the resulting
glibc was working as expected without generating SIGILL.
[ Risks ]
The change is intentionally minimal, smaller than the upstream one, and
only targets the runtime execution. Some tests of the testsuite will
still fail on affected systems. This part can be fixed later in a point
release. This way the risks should be minimal.
[ Checklist ]
[x] *all* changes are documented in the d/changelog
[x] I reviewed all changes and I approve them
[x] attach debdiff against the package in (old)stable
[x] the issue is verified as fixed in unstable
[ Changes ]
The change is very simple and consists in adding a check for BMI2
instructions in the ifunc selector that selects the AVX2 optimized code.
[ Other info ]
Given the severity of the bug, it might be a good idea to release it
through stable-updates.
Adam D. Barratt
Oct 14, 2022, 7:10:04 AM10/14/22
to
Control: tags -1 + confirmed
On Sat, 2022-10-08 at 11:30 +0200, Aurelien Jarno wrote:
> The glibc/2.31-13+deb11u4 update introduced a regression (bug
> #1019855) on some early Intel Haswell processors which expose the
> AVX2 instructions, but lack the BMI2 instructions. On such systems
> the memchr and strlen related functions fails with SIGILL, rendering
> them unusable.
>
> The issue is that some of the backported commits to fix the overflow
> bugs in the AVX2 implementation of wmemchr and wcslen that went in
> the upstream 2.31 branch, started to use BMI2 instructions in
> addition to the AVX2 instructions, without checking for the
> availability of those instructions. This was done in another commit
> that hasn't been backported.
>
> It happens that a microcode update for the affected CPUs (either
> through the BIOS/firmware or from a package) fixes this, so it went
> barely noticed up to now, especially given other distributions
> usually install firmware updates by default.
>
> [ Impact ]
> While the number of affected systems is probably small, this bug
> makes them unusable.
[...]
Regards,
Adam
On Sat, 2022-10-08 at 11:30 +0200, Aurelien Jarno wrote:
> The glibc/2.31-13+deb11u4 update introduced a regression (bug
> #1019855) on some early Intel Haswell processors which expose the
> AVX2 instructions, but lack the BMI2 instructions. On such systems
> the memchr and strlen related functions fails with SIGILL, rendering
> them unusable.
>
> The issue is that some of the backported commits to fix the overflow
> bugs in the AVX2 implementation of wmemchr and wcslen that went in
> the upstream 2.31 branch, started to use BMI2 instructions in
> addition to the AVX2 instructions, without checking for the
> availability of those instructions. This was done in another commit
> that hasn't been backported.
>
> It happens that a microcode update for the affected CPUs (either
> through the BIOS/firmware or from a package) fixes this, so it went
> barely noticed up to now, especially given other distributions
> usually install firmware updates by default.
>
> [ Impact ]
> While the number of affected systems is probably small, this bug
> makes them unusable.
> Given the severity of the bug, it might be a good idea to release it
> through stable-updates.
Please go ahead.
> through stable-updates.
Regards,
Adam
Aurelien Jarno
Oct 14, 2022, 3:50:03 PM10/14/22
to
Hi,
Thanks for the review, I have just uploaded it.
Regards
Aurelien
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aure...@aurel32.net http://www.aurel32.net
Regards
Aurelien
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aure...@aurel32.net http://www.aurel32.net
Adam D Barratt
Oct 15, 2022, 6:50:04 AM10/15/22
to
package release.debian.org
tags 1021426 = bullseye pending
thanks
Hi,
The upload referenced by this bug report has been flagged for acceptance into the proposed-updates queue for Debian bullseye.
Thanks for your contribution!
Upload details
==============
Package: glibc
Version: 2.31-13+deb11u5
Explanation: fix regression in wmemchr and wcslen on CPUs that have AVX2 but not BMI2 (e.g. Intel Haswell)
tags 1021426 = bullseye pending
thanks
Hi,
The upload referenced by this bug report has been flagged for acceptance into the proposed-updates queue for Debian bullseye.
Thanks for your contribution!
Upload details
==============
Package: glibc
Version: 2.31-13+deb11u5
Explanation: fix regression in wmemchr and wcslen on CPUs that have AVX2 but not BMI2 (e.g. Intel Haswell)
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