On Mon, Jul 3, 2023 at 11:08 AM Suren Baghdasaryan <sur...@google.com> wrote:
>
> On Mon, Jul 3, 2023 at 2:53 AM Linux regression tracking (Thorsten
> Leemhuis) <regressi...@leemhuis.info> wrote:
> >
> > On 02.07.23 14:27, Bagas Sanjaya wrote:
> > > I notice a regression report on Bugzilla [1]. Quoting from it:
> > >
> > >> After upgrading to kernel version 6.4.0 from 6.3.9, I noticed frequent 
> > >> but random crashes in a user space program.  After a lot of reduction, I 
> > >> have come up with the following reproducer program:
> > > [...]
> > >> After tuning the various parameters for my computer, exit code 2, which 
> > >> indicates that memory corruption was detected, occurs approximately 99% 
> > >> of the time.  Exit code 1, which occurs approximately 1% of the time, 
> > >> means it ran out of statically-allocated memory before reproducing the 
> > >> issue, and increasing the memory usage any more only leads to 
> > >> diminishing returns.  There is also something like a 0.1% chance that it 
> > >> segfaults due to memory corruption elsewhere than in the 
> > >> statically-allocated buffer.
> > >>
> > >> With this reproducer in hand, I was able to perform the following 
> > >> bisection:
> > > [...]
> > >
> > > See Bugzilla for the full thread.
> >
> > Additional details from
> > https://bugzilla.kernel.org/show_bug.cgi?id=217624#c5 :
> >
> > ```
> > I can confirm that v6.4 with 0bff0aaea03e2a3ed6bfa302155cca8a432a1829
> > reverted no longer causes any memory corruption with either my
> > reproducer or the original program.
> > ```
> >
> > FWIW: 0bff0aaea03 ("x86/mm: try VMA lock-based page fault handling
> > first") [merged for v6.4-rc1, authored by Suren Baghdasaryan [already CCed]]
> >
> > That's the same commit that causes build problems with go:
> >
> > https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf...@kernel.org/
>
> Thanks! I'll investigate this later today. After discussing with
> Andrew, we would like to disable CONFIG_PER_VMA_LOCK by default until
> the issue is fixed. I'll post a patch shortly.

Posted at: 
https://lore.kernel.org/all/20230703182150.2193578-1-sur...@google.com/

>
> >
> > Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> > --
> > Everything you wanna know about Linux kernel regression tracking:
> > https://linux-regtracking.leemhuis.info/about/#tldr
> > If I did something stupid, please tell me, as explained on that page.
> >
> > #regzbot introduced: 0bff0aaea03e2a3

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