From: David Hildenbrand <david@redhat.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Xiongchun duan <duanxiongchun@bytedance.com>,
Markus Elfring <Markus.Elfring@web.de>
Subject: Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
Date: Tue, 14 Apr 2020 14:23:13 +0200 [thread overview]
Message-ID: <f4657c41-b724-30df-86c2-cf3de1873fd9@redhat.com> (raw)
In-Reply-To: <CAMZfGtXnVG8Uny5qnFvHuJqu8UBnatDbfx5kyRQZfDtrGoqwvA@mail.gmail.com>
On 14.04.20 14:09, Muchun Song wrote:
> On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 14.04.20 08:20, Muchun Song wrote:
>>> The find_mergeable_vma can return NULL. In this case, it leads
>>> to crash when we access vma->vm_mm(which's offset is 0x40) in
>>> write_protect_page. And this case did happen on our server. The
>>> following calltrace is captured in kernel 4.19 with ksm enabled.
>>> So add a vma check to fix it.
>>>
>>> --------------------------------------------------------------------------
>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
>>> PGD 0 P4D 0
>>> Oops: 0000 [#1] SMP NOPTI
>>> CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
>>> Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
>>> RIP: 0010:try_to_merge_one_page+0xc7/0x760
>>> Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
>>> 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
>>> 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
>>> RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
>>> RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
>>> RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
>>> RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
>>> R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
>>> R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
>>> FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>> PKRU: 55555554
>>> Call Trace:
>>> ? follow_page_pte+0x36d/0x5e0
>>> ksm_scan_thread+0x115e/0x1960
>>> ? remove_wait_queue+0x60/0x60
>>> kthread+0xf5/0x130
>>> ? try_to_merge_with_ksm_page+0x90/0x90
>>> ? kthread_create_worker_on_cpu+0x70/0x70
>>> ret_from_fork+0x1f/0x30
>>> --------------------------------------------------------------------------
>>>
>>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>>> Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
>>
>> ^ why this signed-off ?
>>
>
> Because I have a partner. And I just sent the v2 patch which updates the
> commit message and patch subject. Thanks for your review.
Then we use Co-developed-by AFAIK instead.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-04-14 12:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-14 6:20 Muchun Song
2020-04-14 11:48 ` David Hildenbrand
2020-04-14 12:09 ` [External] " Muchun Song
2020-04-14 12:23 ` David Hildenbrand [this message]
2020-04-14 13:01 ` Muchun Song
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