On Tue, Jul 04, 2023 at 12:45:39AM -0700, Suren Baghdasaryan wrote: > On Mon, Jul 3, 2023 at 11:44 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Mon, Jul 03, 2023 at 11:27:19AM -0700, Suren Baghdasaryan wrote: > > > On Mon, Jul 3, 2023 at 11:08 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > > > > > > > On Mon, Jul 3, 2023 at 2:53 AM Linux regression tracking (Thorsten > > > > Leemhuis) <regressions@xxxxxxxxxxxxx> 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-e9c6e3cdf51b@xxxxxxxxxx/ > > > > > > > > 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-surenb@xxxxxxxxxx/ > > > > As that change fixes something in 6.4, why not cc: stable on it as well? > > Sorry, I thought since per-VMA locks were introduced in 6.4 and this > patch is fixing 6.4 I didn't need to send it to stable for older > versions. Did I miss something? 6.4.y is a stable kernel tree right now, so yes, it needs to be included there :)
