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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Wenwei Tao <wenwei.tww@alibaba-inc.com>,
	Oleg Nesterov <oleg@redhat.com>,
	David Rientjes <rientjes@google.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: Re: [PATCH] mm, oom: fix potential data corruption when oom_reaper races with writer
Date: Fri, 04 Aug 2017 17:25:46 +0900	[thread overview]
Message-ID: <201708040825.v748Pkul053862@www262.sakura.ne.jp> (raw)
In-Reply-To: <20170804074212.GA26029@dhcp22.suse.cz>

Well, while lockdep warning is gone, this problem is remaining.

diff --git a/mm/memory.c b/mm/memory.c
index edabf6f..1e06c29 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3931,15 +3931,14 @@ int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
        /*
         * This mm has been already reaped by the oom reaper and so the
         * refault cannot be trusted in general. Anonymous refaults would
-        * lose data and give a zero page instead e.g. This is especially
-        * problem for use_mm() because regular tasks will just die and
-        * the corrupted data will not be visible anywhere while kthread
-        * will outlive the oom victim and potentially propagate the date
-        * further.
+        * lose data and give a zero page instead e.g.
         */
-       if (unlikely((current->flags & PF_KTHREAD) && !(ret & VM_FAULT_ERROR)
-                               && test_bit(MMF_UNSTABLE, &vma->vm_mm->flags)))
+       if (unlikely(!(ret & VM_FAULT_ERROR)
+                    && test_bit(MMF_UNSTABLE, &vma->vm_mm->flags))) {
+               if (ret & VM_FAULT_RETRY)
+                       down_read(&vma->vm_mm->mmap_sem);
                ret = VM_FAULT_SIGBUS;
+       }

        return ret;
 }

$ cat /tmp/file.* | od -b | head
0000000 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
*
420330000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000
*
420340000 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
*
457330000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000
*
457340000 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
*

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  reply	other threads:[~2017-08-04  8:25 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-03 13:59 [PATCH] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
2017-08-03 13:59 ` Michal Hocko
2017-08-04  6:46 ` Tetsuo Handa
2017-08-04  7:42   ` Michal Hocko
2017-08-04  7:42     ` Michal Hocko
2017-08-04  8:25     ` Tetsuo Handa [this message]
2017-08-04  8:32       ` Michal Hocko
2017-08-04  8:32         ` 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           ` Michal Hocko
2017-08-04  8:33           ` [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
2017-08-04  8:33             ` Michal Hocko
2017-08-04  9:16       ` Re: [PATCH] " Michal Hocko
2017-08-04  9:16         ` Michal Hocko
2017-08-04 10:41         ` Tetsuo Handa
2017-08-04 10:41           ` Tetsuo Handa
2017-08-04 11:00           ` Michal Hocko
2017-08-04 11:00             ` Michal Hocko
2017-08-04 14:56             ` Michal Hocko
2017-08-04 14:56               ` Michal Hocko
2017-08-04 16:49               ` Tetsuo Handa
2017-08-04 16:49                 ` Tetsuo Handa
2017-08-05  1:46               ` 陶文苇
2017-08-05  1:46                 ` 陶文苇

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