From nobody Tue Apr 7 16:28:41 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FBFDECAAD4 for ; Fri, 26 Aug 2022 15:16:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344424AbiHZPQr (ORCPT ); Fri, 26 Aug 2022 11:16:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344499AbiHZPPi (ORCPT ); Fri, 26 Aug 2022 11:15:38 -0400 Received: from mail-lf1-x14a.google.com (mail-lf1-x14a.google.com [IPv6:2a00:1450:4864:20::14a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6E3DBBBA66 for ; Fri, 26 Aug 2022 08:10:16 -0700 (PDT) Received: by mail-lf1-x14a.google.com with SMTP id y3-20020a197503000000b00492f3a13baeso294275lfe.12 for ; Fri, 26 Aug 2022 08:10:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc; bh=dGjdyFKcPZ8AZlzw9ep1EXgYBHGgW0m7GguSz7kBI6Q=; b=DZGsI9l3W9MQLA+ou9XdSB4IZE46ComuEd6rS14iWZ0xSDfAJ+BWwB8A7M05fO5zjT Wh7mYAH6WAAzh+FI/uVm5Ljcf9NEeu2Z9UZM+4qfZzFoj+6Fh/tecr4Yol7TBl6MiU/L tCTqBg9m2iJte3DzNqf8V7ws94Br5Wtp68vVWk7plrk6xmxEjPcPZVSvIrk/LnFF/INL 93xvlWF5Ha1xHXpbxLntxctwzalog3vxzBxrVMuGDkqbsYK5RzyESy+/nuRwFZ41sSYu t2owLKhR+yzd+pCanHFbrVCWUmN1zsn8mhRcH/6ROVVHuRMuA9Jhn32qCWbGf06hi10p XV8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc; bh=dGjdyFKcPZ8AZlzw9ep1EXgYBHGgW0m7GguSz7kBI6Q=; b=LxFSpg+X03p3C7kvv8NQJ0Brx0lw1h8AcnmMeWsRRAh9eX3UVQPaoe32MVMZpoFwtt yCAOU8wApwwBpzDqxpKcF154FM0OLT9KvnltnZffk82EkwmJRHAjGu3IFKdsppK877uE eet1UMs2Gw2BFgNLEjGngqlD9XQlpDDVJDiEtvMRJ3rgsqpWRFlAWvVz0B7lSvQzIG0n P2vwHAAsiKJ4+bL4jSQwsieKuuxBk/UWX8DmasGgFxc2Kmk9nVb+Hqy1+OR01dOBo35Z wXpRzBgSxU24tne/UnDLh3K0hD31ZsPW1ADCid8bZncGxkxz1YaogKrqPcykBMlZUlZb zBcw== X-Gm-Message-State: ACgBeo0ojgE8UAIV7KmJ0pHGaTz4YuG0mc1IBfLOhCIZZ30Tt2oc0MVP MBB7/XUcc1NBoDBWOS5jUDuph3gKZlE= X-Google-Smtp-Source: AA6agR5+Ww/s7u4XD1azUk5I5ZYmSipZxiExxoopJysRcyPZ8zjk++GJnOf429p9ygUYKujEBktJ1Rf+Pzg= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:5207:ac36:fdd3:502d]) (user=glider job=sendgmr) by 2002:a05:6512:3054:b0:48a:f489:1d68 with SMTP id b20-20020a056512305400b0048af4891d68mr2401202lfb.260.1661526613226; Fri, 26 Aug 2022 08:10:13 -0700 (PDT) Date: Fri, 26 Aug 2022 17:08:06 +0200 In-Reply-To: <20220826150807.723137-1-glider@google.com> Mime-Version: 1.0 References: <20220826150807.723137-1-glider@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220826150807.723137-44-glider@google.com> Subject: [PATCH v5 43/44] mm: fs: initialize fsdata passed to write_begin/write_end interface From: Alexander Potapenko To: glider@google.com Cc: Alexander Viro , Alexei Starovoitov , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Functions implementing the a_ops->write_end() interface accept the `void *fsdata` parameter that is supposed to be initialized by the corresponding a_ops->write_begin() (which accepts `void **fsdata`). However not all a_ops->write_begin() implementations initialize `fsdata` unconditionally, so it may get passed uninitialized to a_ops->write_end(), resulting in undefined behavior. Fix this by initializing fsdata with NULL before the call to write_begin(), rather than doing so in all possible a_ops implementations. This patch covers only the following cases found by running x86 KMSAN under syzkaller: - generic_perform_write() - cont_expand_zero() and generic_cont_expand_simple() - page_symlink() Other cases of passing uninitialized fsdata may persist in the codebase. Signed-off-by: Alexander Potapenko --- Link: https://linux-review.googlesource.com/id/Ie300c21bbe9dea69a730745bd3c= 6d2720953bf41 --- fs/buffer.c | 4 ++-- fs/namei.c | 2 +- mm/filemap.c | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/buffer.c b/fs/buffer.c index 55e762a58eb65..e1198f4b28c8f 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2352,7 +2352,7 @@ int generic_cont_expand_simple(struct inode *inode, l= off_t size) struct address_space *mapping =3D inode->i_mapping; const struct address_space_operations *aops =3D mapping->a_ops; struct page *page; - void *fsdata; + void *fsdata =3D NULL; int err; =20 err =3D inode_newsize_ok(inode, size); @@ -2378,7 +2378,7 @@ static int cont_expand_zero(struct file *file, struct= address_space *mapping, const struct address_space_operations *aops =3D mapping->a_ops; unsigned int blocksize =3D i_blocksize(inode); struct page *page; - void *fsdata; + void *fsdata =3D NULL; pgoff_t index, curidx; loff_t curpos; unsigned zerofrom, offset, len; diff --git a/fs/namei.c b/fs/namei.c index 53b4bc094db23..076ae96ca0b14 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -5088,7 +5088,7 @@ int page_symlink(struct inode *inode, const char *sym= name, int len) const struct address_space_operations *aops =3D mapping->a_ops; bool nofs =3D !mapping_gfp_constraint(mapping, __GFP_FS); struct page *page; - void *fsdata; + void *fsdata =3D NULL; int err; unsigned int flags; =20 diff --git a/mm/filemap.c b/mm/filemap.c index 15800334147b3..ada25b9f45ad1 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3712,7 +3712,7 @@ ssize_t generic_perform_write(struct kiocb *iocb, str= uct iov_iter *i) unsigned long offset; /* Offset into pagecache page */ unsigned long bytes; /* Bytes to write to page */ size_t copied; /* Bytes copied from user */ - void *fsdata; + void *fsdata =3D NULL; =20 offset =3D (pos & (PAGE_SIZE - 1)); bytes =3D min_t(unsigned long, PAGE_SIZE - offset, --=20 2.37.2.672.g94769d06f0-goog