From: Andrew Morton <akpm@linux-foundation.org>
To: Suren Baghdasaryan <surenb@google.com>
Cc: mhocko@kernel.org, mhocko@suse.com, rientjes@google.com,
willy@infradead.org, hannes@cmpxchg.org, guro@fb.com,
riel@surriel.com, minchan@kernel.org, christian@brauner.io,
hch@infradead.org, oleg@redhat.com, david@redhat.com,
jannh@google.com, shakeelb@google.com, luto@kernel.org,
christian.brauner@ubuntu.com, fweimer@redhat.com,
jengelh@inai.de, linux-api@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH 1/1] mm: prevent a race between process_mrelease and exit_mmap
Date: Thu, 21 Oct 2021 19:24:54 -0700 [thread overview]
Message-ID: <20211021192454.72ada9b3d59460cc3c037d2c@linux-foundation.org> (raw)
In-Reply-To: <20211022014658.263508-1-surenb@google.com>
On Thu, 21 Oct 2021 18:46:58 -0700 Suren Baghdasaryan <surenb@google.com> wrote:
> Race between process_mrelease and exit_mmap, where free_pgtables is
> called while __oom_reap_task_mm is in progress, leads to kernel crash
> during pte_offset_map_lock call. oom-reaper avoids this race by setting
> MMF_OOM_VICTIM flag and causing exit_mmap to take and release
> mmap_write_lock, blocking it until oom-reaper releases mmap_read_lock.
> Reusing MMF_OOM_VICTIM for process_mrelease would be the simplest way to
> fix this race, however that would be considered a hack. Fix this race
> by elevating mm->mm_users and preventing exit_mmap from executing until
> process_mrelease is finished. Patch slightly refactors the code to adapt
> for a possible mmget_not_zero failure.
> This fix has considerable negative impact on process_mrelease performance
> and will likely need later optimization.
Has the impact been quantified?
And where's the added cost happening? The changes all look quite
lightweight?
next prev parent reply other threads:[~2021-10-22 2:25 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-22 1:46 Suren Baghdasaryan
2021-10-22 2:24 ` Andrew Morton [this message]
2021-10-22 5:23 ` Suren Baghdasaryan
2021-10-22 8:03 ` Michal Hocko
2021-10-22 11:32 ` Matthew Wilcox
2021-10-22 12:04 ` Michal Hocko
2021-10-22 17:38 ` Suren Baghdasaryan
2021-10-27 16:08 ` Suren Baghdasaryan
2021-10-27 17:33 ` Matthew Wilcox
2021-10-27 17:42 ` Suren Baghdasaryan
2021-10-27 17:51 ` Matthew Wilcox
2021-10-27 18:00 ` Suren Baghdasaryan
2021-10-29 13:03 ` Michal Hocko
2021-10-29 16:07 ` Suren Baghdasaryan
2021-11-01 8:37 ` Michal Hocko
2021-11-01 15:44 ` Suren Baghdasaryan
2021-11-01 19:59 ` Suren Baghdasaryan
2021-11-02 7:58 ` Michal Hocko
2021-11-02 15:14 ` Suren Baghdasaryan
2021-11-09 19:01 ` Suren Baghdasaryan
2021-11-09 19:26 ` Michal Hocko
2021-11-09 19:37 ` Suren Baghdasaryan
2021-11-09 19:50 ` Michal Hocko
2021-11-09 20:02 ` Suren Baghdasaryan
2021-11-09 20:10 ` Michal Hocko
2021-11-09 21:10 ` Suren Baghdasaryan
2021-11-11 1:49 ` Suren Baghdasaryan
2021-11-11 9:20 ` Michal Hocko
2021-11-11 15:02 ` Suren Baghdasaryan
2021-11-12 8:58 ` Michal Hocko
2021-11-12 16:00 ` Suren Baghdasaryan
2021-11-09 19:41 ` Michal Hocko
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