2020-07-21 14:55:48

by Paul Menzel

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Subject: [Regression] hangs caused by commit 3202fa62fb (slub: relocate freelist pointer to middle of object)

Dear Kees, dear Andrew,


No idea, if you are aware of it yet, but three people verified that
commit 3202fa62fb (slub: relocate freelist pointer to middle of object)
causes a regression on AMD hardware [1].

It’d be great, if you took a look, and advised if this commit (and
follow-ups) should be reverted, until the issue is analyzed.


Kind regards,

Paul


[1]: https://bugzilla.kernel.org/show_bug.cgi?id=207383
"[Regression] 5.7 amdgpu/polaris11 gpf: amdgpu_atomic_commit_tail"


2020-07-21 19:03:10

by Kees Cook

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Subject: Re: [Regression] hangs caused by commit 3202fa62fb (slub: relocate freelist pointer to middle of object)

On Tue, Jul 21, 2020 at 04:55:12PM +0200, Paul Menzel wrote:
> No idea, if you are aware of it yet, but three people verified that commit
> 3202fa62fb (slub: relocate freelist pointer to middle of object) causes a
> regression on AMD hardware [1].

Hi, thanks for emailing; I don't get bugzilla notifications, so I hadn't
seen this yet.

> It’d be great, if you took a look, and advised if this commit (and
> follow-ups) should be reverted, until the issue is analyzed.

There have been a number of fixes to that commit (which I see are
mentioned in a quick skim of the bug), but they've mostly been around
additional slab debugging features. If it's causing a problem outside
of that, my instinct would be there might be a use-after-free happening,
but I'll go read the bug more closely now, and comment there (or here,
if needed).

Thanks!

--
Kees Cook