From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: mhocko@kernel.org, akpm@linux-foundation.org
Cc: andrea@kernel.org, kirill@shutemov.name, oleg@redhat.com,
wenwei.tww@alibaba-inc.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, mhocko@suse.com
Subject: Re: [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer
Date: Fri, 11 Aug 2017 11:28:52 +0900 [thread overview]
Message-ID: <201708111128.FEE39036.HFVSQFOtOMLFJO@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20170807113839.16695-3-mhocko@kernel.org>
Michal Hocko wrote:
> +/*
> + * Checks whether a page fault on the given mm is still reliable.
> + * This is no longer true if the oom reaper started to reap the
> + * address space which is reflected by MMF_UNSTABLE flag set in
> + * the mm. At that moment any !shared mapping would lose the content
> + * and could cause a memory corruption (zero pages instead of the
> + * original content).
> + *
> + * User should call this before establishing a page table entry for
> + * a !shared mapping and under the proper page table lock.
> + *
> + * Return 0 when the PF is safe VM_FAULT_SIGBUS otherwise.
> + */
> +static inline int check_stable_address_space(struct mm_struct *mm)
> +{
> + if (unlikely(test_bit(MMF_UNSTABLE, &mm->flags)))
> + return VM_FAULT_SIGBUS;
> + return 0;
> +}
> +
Will you explain the mechanism why random values are written instead of zeros
so that this patch can actually fix the race problem? I consider that writing
random values (though it seems like portion of process image) instead of zeros
to a file might cause a security problem, and the patch that fixes it should be
able to be backported to stable kernels.
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next prev parent reply other threads:[~2017-08-11 2:29 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-07 11:38 [PATCH 0/2] mm, oom: fix oom_reaper fallouts Michal Hocko
2017-08-07 11:38 ` [PATCH 1/2] mm: fix double mmap_sem unlock on MMF_UNSTABLE enforced SIGBUS Michal Hocko
2017-08-15 0:49 ` David Rientjes
2017-08-07 11:38 ` [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
2017-08-08 17:48 ` Andrea Arcangeli
2017-08-08 23:35 ` Tetsuo Handa
2017-08-09 18:36 ` Andrea Arcangeli
2017-08-10 8:21 ` Michal Hocko
2017-08-10 13:33 ` Michal Hocko
2017-08-11 2:28 ` Tetsuo Handa [this message]
2017-08-11 7:09 ` Michal Hocko
2017-08-11 7:54 ` Tetsuo Handa
2017-08-11 10:22 ` Andrea Arcangeli
2017-08-11 10:42 ` Andrea Arcangeli
2017-08-11 11:53 ` Tetsuo Handa
2017-08-11 12:08 ` Michal Hocko
2017-08-11 15:46 ` Tetsuo Handa
2017-08-14 13:59 ` Michal Hocko
2017-08-14 22:51 ` Tetsuo Handa
2017-08-15 6:55 ` Michal Hocko
2017-08-15 8:41 ` Michal Hocko
2017-08-15 10:06 ` Tetsuo Handa
2017-08-15 12:26 ` Michal Hocko
2017-08-15 12:58 ` Tetsuo Handa
2017-08-17 13:58 ` Michal Hocko
2017-08-15 5:30 ` Tetsuo Handa
2017-08-07 13:28 ` [PATCH 0/2] mm, oom: fix oom_reaper fallouts Tetsuo Handa
2017-08-07 14:04 ` Michal Hocko
2017-08-07 15:23 ` Tetsuo Handa
2017-08-15 12:29 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2017-08-04 8:32 Re: [PATCH] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
2017-08-04 8:33 ` [PATCH 1/2] mm: fix double mmap_sem unlock on MMF_UNSTABLE enforced SIGBUS Michal Hocko
2017-08-04 8:33 ` [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
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