From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BD01C2BA19 for ; Tue, 14 Apr 2020 13:01:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EC0D12075E for ; Tue, 14 Apr 2020 13:01:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=bytedance-com.20150623.gappssmtp.com header.i=@bytedance-com.20150623.gappssmtp.com header.b="Q3AFN5Io" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC0D12075E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9E2F68E0005; Tue, 14 Apr 2020 09:01:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B9F48E0001; Tue, 14 Apr 2020 09:01:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D0198E0005; Tue, 14 Apr 2020 09:01:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id 73D8D8E0001 for ; Tue, 14 Apr 2020 09:01:57 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 43BAC584D for ; Tue, 14 Apr 2020 13:01:57 +0000 (UTC) X-FDA: 76706473074.21.copy89_2e139f2a74d44 X-HE-Tag: copy89_2e139f2a74d44 X-Filterd-Recvd-Size: 5826 Received: from mail-il1-f196.google.com (mail-il1-f196.google.com [209.85.166.196]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Tue, 14 Apr 2020 13:01:56 +0000 (UTC) Received: by mail-il1-f196.google.com with SMTP id u5so4829368ilb.5 for ; Tue, 14 Apr 2020 06:01:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2zyeYMBiZ7mbLAhDaBruYWCix3rdWMBYNww9cQF5pTg=; b=Q3AFN5IoWsmLuGbfJMknS+4eK5SKwEYNdDjDtHmK79XnOpMkDoA6sCplhBXWSUiYLF glxxxKdCSw1JLfM1Fsv3khF+ynyElC5fh0mZkfU1EcjJJuwjYilEgZsSQcMZPBlweyB4 fmGAQTHc7YAoFxI76hvFKwnNqqwslQbu5kgC04gih2DGoHy3qhUj50fjUnyqFNohQKLt 62yE4mgNzUDMMhcUwOedk7MShJVD6v+St96RPT01u1f6BKcJPdE1/TktTr1g9iLwTfH1 7x0rGzc9y63wkL3Ob6d84lQ+ykiL6g+9e5ox8/dFWUOiXJ6Uav/YEQhJ0ZcIJBFBaukD 1unQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2zyeYMBiZ7mbLAhDaBruYWCix3rdWMBYNww9cQF5pTg=; b=DNgQiidMpLZl10Msla/OgwHbPdE0qoH8N1fss+mcEGfBJztRbkfPXAnNBIkNCOaHQB FD/RyKErLOth/OXMDoiKXpTmLWS7cDOpiek4wZLqfa7Hd74PNbOvxwNFpuwxjvCpkB8m OD4IESJ/1I87ZN35//glCTVgXMuG3glr1ayoR4dbwEhgwyCt53bArF9atia8nqyCBo68 +cEPBSXPI9LgoYlw0fL18AvVYU+SxmP3K4+J4g6dFSBJ2fz2xgcHle1e/1hdJgfWfoGm XSkCWl5WBd90dbhXEHyHwkXtCtRf/a7R0o58KLyNIoh00KoeAwzgszznOlvwdByFp2T/ VBfA== X-Gm-Message-State: AGi0PubwA3/EZmJLwc0uKGwTXLQVQrQKY4QGyTn9I8uD1b7HvYTLuy90 dxYh0l2U/4kUzepPPiDdMq3H8P1DLtFVdNmrtQ8Ytg== X-Google-Smtp-Source: APiQypK/rt/43+1B/TcFGkTZRqd7u4Nt5XX2Ti1tGVnMbPfH7K2bSLMzJV4Scxi2cE1qB84QrUc6gWQ+EINE4YrwhoM= X-Received: by 2002:a92:5b56:: with SMTP id p83mr96528ilb.70.1586869315654; Tue, 14 Apr 2020 06:01:55 -0700 (PDT) MIME-Version: 1.0 References: <20200414062050.66644-1-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Tue, 14 Apr 2020 21:01:19 +0800 Message-ID: Subject: Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040 To: David Hildenbrand Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiongchun duan , Markus Elfring Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 14, 2020 at 8:23 PM David Hildenbrand wrote: > > On 14.04.20 14:09, Muchun Song wrote: > > On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand 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 > >>> Signed-off-by: Xiongchun duan > >> > >> ^ 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 a lot. I will fix it. -- Yours, Muchun