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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 241B9C2BA19 for ; Tue, 14 Apr 2020 12:10:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CBFFB2075E for ; Tue, 14 Apr 2020 12:10:24 +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="UXsJOXIe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBFFB2075E 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 74AD78E0003; Tue, 14 Apr 2020 08:10:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6FBFC8E0001; Tue, 14 Apr 2020 08:10:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 60FD88E0003; Tue, 14 Apr 2020 08:10:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id 456278E0001 for ; Tue, 14 Apr 2020 08:10:24 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id ECCFA181AEF1E for ; Tue, 14 Apr 2020 12:10:23 +0000 (UTC) X-FDA: 76706343126.29.fan70_20793e930160f X-HE-Tag: fan70_20793e930160f X-Filterd-Recvd-Size: 6461 Received: from mail-io1-f67.google.com (mail-io1-f67.google.com [209.85.166.67]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Tue, 14 Apr 2020 12:10:23 +0000 (UTC) Received: by mail-io1-f67.google.com with SMTP id o127so12981274iof.0 for ; Tue, 14 Apr 2020 05:10:22 -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=sAdVxxSK6UzybtZESb3uXkMXP8dhayxHiMBPeS5kvUk=; b=UXsJOXIe8Eifex9TCUfwki7mv+EZmx/jqu4JkkaKE9/C3kFVVSJLzxbf1tHMrKrQug qgHamelknoE44KAA3kHNmTdoIePmtz9vycqFHzFaHCRi9ffZq879LzAwVt5iqK90fJ3U 5Q0SCVNMA5zjL/aG93IsbXxsh1Qm9UdDyIh88ZpNzX7W4C6GvcDZYDarzpt5rp3rXcdr Wf1O4OEr+fEqT0aXOwTYzN3/9GUDcICMbQF5XfHaB9zQ5mAks+MxkRZGGYRPn/1hOTVJ Bh9TxqRBiXrl1tph0YcYQqrNwYpKBIa5nHPGZ+DCYfM0WLczeTALMk0tyl0TLlvgIpzW vUeA== 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=sAdVxxSK6UzybtZESb3uXkMXP8dhayxHiMBPeS5kvUk=; b=rCO9OO/5d2RtyZ39cDwWbTvZzlDxfT2I7ZvW8bhOhwp1tvdojeY4nzRZvYcv6cD3G4 8JbTAKruLAPVd7skImGIi13sMB8Ru99+0EYC4/1Q9IDFdDOEPIgPSS4FabcGJsVXGaLZ KfFR4vuMlreTPPfX9aYEP+qsmTTZpuVf/bARmEtm4XWV/6BFniBrW2jKgtV4rU54RqQm XDuabPDFjDomccEXmVLGNsxYWFC4/OOQWkPHJdcm47o4ltYMx8+5K7MZgcEkMe5bNsGT e1YfoHw+MUXAUvrF/KcoP5c04vEf2+0exxNRr47hQKg0y2EjTFpKaaDZ3UiOqTpgPc/r tDWw== X-Gm-Message-State: AGi0Pua2rrqm8v36hx4zdKxLQdTr9qNXT7F1bGjuRKGwU0LFNKRExAv4 DaRZSTyDOKQ9PXskJSZSprM6Q0ZaN8qtwNuimlI5Dg== X-Google-Smtp-Source: APiQypLGxrdeIAqKDuz8J7dHMNCNliab8V1lHrPvVF9wPSALeTIZ7l/PJ0lcxD0CjYGKrmpmMHbAQBT2l9+/UnJ4Z9Q= X-Received: by 2002:a02:cca3:: with SMTP id t3mr12777843jap.3.1586866221756; Tue, 14 Apr 2020 05:10:21 -0700 (PDT) MIME-Version: 1.0 References: <20200414062050.66644-1-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Tue, 14 Apr 2020 20:09:45 +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 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. > > --- > > mm/ksm.c | 7 +++++-- > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > diff --git a/mm/ksm.c b/mm/ksm.c > > index a558da9e71770..69b2f85e22d5b 100644 > > --- a/mm/ksm.c > > +++ b/mm/ksm.c > > @@ -2112,8 +2112,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) > > > > down_read(&mm->mmap_sem); > > vma = find_mergeable_vma(mm, rmap_item->address); > > - err = try_to_merge_one_page(vma, page, > > - ZERO_PAGE(rmap_item->address)); > > + if (vma) > > + err = try_to_merge_one_page(vma, page, > > + ZERO_PAGE(rmap_item->address)); > > + else > > + err = -EFAULT; > > up_read(&mm->mmap_sem); > > /* > > * In case of failure, the page was not really empty, so we > > > > Reviewed-by: David Hildenbrand > > -- > Thanks, > > David / dhildenb > -- Yours, Muchun