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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18F65C7EE25 for ; Thu, 8 Jun 2023 02:34:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 838F5900002; Wed, 7 Jun 2023 22:34:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7E9556B0074; Wed, 7 Jun 2023 22:34:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6B0C5900002; Wed, 7 Jun 2023 22:34:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 5B2316B0072 for ; Wed, 7 Jun 2023 22:34:11 -0400 (EDT) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id F19A740319 for ; Thu, 8 Jun 2023 02:34:10 +0000 (UTC) X-FDA: 80878011060.12.0342CF6 Received: from mail-qv1-f53.google.com (mail-qv1-f53.google.com [209.85.219.53]) by imf10.hostedemail.com (Postfix) with ESMTP id 30C3EC0002 for ; Thu, 8 Jun 2023 02:34:09 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=G0obPoIN; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf10.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.219.53 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1686191649; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=uP40DkHZE8fMAP8vvdgFF2kWzyMWQZR4DZPduOdwDWQ=; b=gjHApMqASX/OL0LVZVii5YGaACrCnoH0jTjPW09qF2IGrXap/F35tGg9oSNGpEtTgIKGxC Dg7++uDIEDKLEbQbzJobem8VPBtTQQQCaUFl8JtuNljoR6N4RsoCPUYcd/AbKLfu7KlG7j lNKxDIL0lgSt26JeKH1WNyYVBzYEu38= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=G0obPoIN; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf10.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.219.53 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1686191649; a=rsa-sha256; cv=none; b=j55PS2tpmVTQzCbQBsgFmljXqf5iDI0IZhq856R8mYxoriyTuGdZWZhZbnTHCGiRZAtDHR HAHWb4+eqYI2D7xX0N7spdf2vfHpRaeQ6mjggVFhcHBLozUolIQzcLnkUwQ5R16eTMBATA XThxpF8jKOMZMOZG/ZzQxz5rcWhq+gU= Received: by mail-qv1-f53.google.com with SMTP id 6a1803df08f44-62b68ce199bso1548646d6.0 for ; Wed, 07 Jun 2023 19:34:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1686191648; x=1688783648; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=uP40DkHZE8fMAP8vvdgFF2kWzyMWQZR4DZPduOdwDWQ=; b=G0obPoIN8utqPXiuq/+nMv0epDlB1dzGm/vjM7bcGwptd1Jn6kyG8HWxD9YXpN/cm+ mSb8p2kzKNMz8QvIXEZPRHGcz+pppRanKsWlAHMS6uoiT4FAal411F5XIqwbNnGvUP71 lEHnsSlMV2ICiGwkrAiKFiKTnD5BTQAvfeeG1786OX8MSW60LUkgZVqfqvY0M8AxfxFS DSGJx7uM8VBV4knFc1yBhpt7p63HCkykjLpiaCVYcB60l+iO9F8XNQv5G58PF1fcsJhw 2Rx9nmvOmRgdBrs82YierCWnRBLm+xii0qax286v7BLUVt8ay3El2nCuyAUX13ko5Fm2 HIsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686191648; x=1688783648; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=uP40DkHZE8fMAP8vvdgFF2kWzyMWQZR4DZPduOdwDWQ=; b=GdRYG3Q0AfE+9k/G8iHJ5E/5GFdeysz2EbVaqqh76aoy5c7CeZwyKi6hcRAVuish3k z4bln26/GDSNDlHce0ycuLLmaLGbcI80+aSGLGSUfsXq1yQJti+DldlIIn/Itb+7G23A rTSe50l23niW3brzSU40yKcISE6KGVYhqvFZNH8w5CsYYbsULbOPtVZTAQl0WkET0BYu fJ/iX8UZSf2a/Ux5aqMWnS00y7SITu8cBLZPL5mHTh4jJSjFUJHQXTmmiD7zevxpM4b/ Ofj9/QeUyPEoPFwk1QusDmVfq8XLYMXZyxbnN0bg+n/2mXpkZ5EYuEnjAXfGGX78Hubw V24Q== X-Gm-Message-State: AC+VfDwCRGFhmDv93Wqv6dfZlDluCMvWX79S8CN6j5D8KVzVvALE8Zc7 AEQ3Lfl5ZoSGOGQjTX+ES+DRnmhwE4lGz0d+cZg= X-Google-Smtp-Source: ACHHUZ5gPVxw/28i5FilUmnhbMAE2AV8ykYXtiYaqW0G3GBqN7vSor/zNpBGMX/7DPaEu6m3yvv4BbB4Ws/Z3to+T9o= X-Received: by 2002:a05:6214:1c4b:b0:5f1:606b:a9c8 with SMTP id if11-20020a0562141c4b00b005f1606ba9c8mr262744qvb.22.1686191648232; Wed, 07 Jun 2023 19:34:08 -0700 (PDT) MIME-Version: 1.0 References: <20230606233613.1290819-1-aquini@redhat.com> In-Reply-To: <20230606233613.1290819-1-aquini@redhat.com> From: Yafang Shao Date: Thu, 8 Jun 2023 10:33:31 +0800 Message-ID: Subject: Re: [PATCH] writeback: fix dereferencing NULL mapping->host on writeback_page_template To: Rafael Aquini Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Aristeu Rozanski Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 30C3EC0002 X-Stat-Signature: rdck7w69iuus9kjuybnnrfnwzn5ca5qh X-HE-Tag: 1686191649-931166 X-HE-Meta: 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 Evah8Xjr BB0JQs6xoZ36cSojnmMv1dS1AhzDcCJXtWX8dF2YkDrqhIaHLUuX/nV0ilb4J+bKjxb8715dwKf0HrxLS20AN6nFCbxbToUFfu825J8tQOCYZwJrD8Rc48qe8UgYyzMJb1NzqS3pdds90F9DwTJGswPpqMQCZg0MUgGls1ktaFkdCTV+USTN+D1XI4Qn818XBKk7uLfFkGtrf6+x9WlRkLj9RfujW9yXvccIWCC6CreUYfowqkuCoV7NL/OMbDRV2myxjzvHtWUDbwNVq1YF2t4vydVxNUYRYZqxFN5LhLi9iWRrIBy0SD7TiVWvcA9z3w5bHx01+XtsG5Bgkz2EOkSdkUUjQ/0A7U/kc+GgMl9WqUaScB//bgmzYVIARLfMcMlOPQ0BD/b1zYpccvB39poyAZD+48ylNcG3X7/pdhOH4H5cz62z+QgUHpl1UtFNL5q/1YCWLI1PNSUSjRcvxVM4trp7m+CKGDXS3 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 Wed, Jun 7, 2023 at 7:37=E2=80=AFAM Rafael Aquini wr= ote: > > When commit 19343b5bdd16 ("mm/page-writeback: introduce tracepoint for > wait_on_page_writeback()") repurposed the writeback_dirty_page trace even= t > as a template to create its new wait_on_page_writeback trace event, it > ended up opening a window to NULL pointer dereference crashes due to > the (infrequent) occurrence of a race where an access to a page in the > swap-cache happens concurrently with the moment this page is being > written to disk and the tracepoint is enabled: > > BUG: kernel NULL pointer dereference, address: 0000000000000040 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 800000010ec0a067 P4D 800000010ec0a067 PUD 102353067 PMD 0 > Oops: 0000 [#1] PREEMPT SMP PTI > CPU: 1 PID: 1320 Comm: shmem-worker Kdump: loaded Not tainted 6.4.0-r= c5+ #13 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-2023030= 1gitf80f052277c8-1.fc37 03/01/2023 > RIP: 0010:trace_event_raw_event_writeback_folio_template+0x76/0xf0 > Code: 4d 85 e4 74 5c 49 8b 3c 24 e8 06 98 ee ff 48 89 c7 e8 9e 8b ee = ff ba 20 00 00 00 48 89 ef 48 89 c6 e8 fe d4 1a 00 49 8b 04 24 <48> 8b 40 4= 0 48 89 43 28 49 8b 45 20 48 89 e7 48 89 43 30 e8 a2 4d > RSP: 0000:ffffaad580b6fb60 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: ffff90e38035c01c RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff90e38035c044 > RBP: ffff90e38035c024 R08: 0000000000000002 R09: 0000000000000006 > R10: ffff90e38035c02e R11: 0000000000000020 R12: ffff90e380bac000 > R13: ffffe3a7456d9200 R14: 0000000000001b81 R15: ffffe3a7456d9200 > FS: 00007f2e4e8a15c0(0000) GS:ffff90e3fbc80000(0000) knlGS:000000000= 0000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000040 CR3: 00000001150c6003 CR4: 0000000000170ee0 > Call Trace: > > ? __die+0x20/0x70 > ? page_fault_oops+0x76/0x170 > ? kernelmode_fixup_or_oops+0x84/0x110 > ? exc_page_fault+0x65/0x150 > ? asm_exc_page_fault+0x22/0x30 > ? trace_event_raw_event_writeback_folio_template+0x76/0xf0 > folio_wait_writeback+0x6b/0x80 > shmem_swapin_folio+0x24a/0x500 > ? filemap_get_entry+0xe3/0x140 > shmem_get_folio_gfp+0x36e/0x7c0 > ? find_busiest_group+0x43/0x1a0 > shmem_fault+0x76/0x2a0 > ? __update_load_avg_cfs_rq+0x281/0x2f0 > __do_fault+0x33/0x130 > do_read_fault+0x118/0x160 > do_pte_missing+0x1ed/0x2a0 > __handle_mm_fault+0x566/0x630 > handle_mm_fault+0x91/0x210 > do_user_addr_fault+0x22c/0x740 > exc_page_fault+0x65/0x150 > asm_exc_page_fault+0x22/0x30 > > This problem arises from the fact that the repurposed writeback_dirty_pag= e > trace event code was written assuming that every pointer to mapping > (struct address_space) would come from a file-mapped page-cache object, > thus mapping->host would always be populated, and that was a valid case > before commit 19343b5bdd16. The swap-cache address space (swapper_spaces)= , > however, doesn't populate its ->host (struct inode) pointer, thus leading > to the crashes in the corner-case aforementioned. > > commit 19343b5bdd16 ended up breaking the assignment of __entry->name and > __entry->ino for the wait_on_page_writeback tracepoint -- both dependent > on mapping->host carrying a pointer to a valid inode. The assignment of > __entry->name was fixed by commit 68f23b89067f ("memcg: fix a crash in > wb_workfn when a device disappears"), and this commit fixes the remaining > case, for __entry->ino. > > Fixes: 19343b5bdd16 ("mm/page-writeback: introduce tracepoint for wait_on= _page_writeback()") > Signed-off-by: Rafael Aquini Thanks for your fix! Reviewed-by: Yafang Shao > --- > include/trace/events/writeback.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/trace/events/writeback.h b/include/trace/events/writ= eback.h > index 86b2a82da546..54e353c9f919 100644 > --- a/include/trace/events/writeback.h > +++ b/include/trace/events/writeback.h > @@ -68,7 +68,7 @@ DECLARE_EVENT_CLASS(writeback_folio_template, > strscpy_pad(__entry->name, > bdi_dev_name(mapping ? inode_to_bdi(mapping->= host) : > NULL), 32); > - __entry->ino =3D mapping ? mapping->host->i_ino : 0; > + __entry->ino =3D (mapping && mapping->host) ? mapping->ho= st->i_ino : 0; > __entry->index =3D folio->index; > ), > > -- > 2.39.2 > --=20 Regards Yafang