From nobody Mon Apr 6 18:42:50 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 B48E2ECAAD3 for ; Mon, 5 Sep 2022 12:34:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238014AbiIEMeN (ORCPT ); Mon, 5 Sep 2022 08:34:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238206AbiIEMck (ORCPT ); Mon, 5 Sep 2022 08:32:40 -0400 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7F9486173F for ; Mon, 5 Sep 2022 05:26:58 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id p4-20020a056402500400b00447e8b6f62bso5760510eda.17 for ; Mon, 05 Sep 2022 05:26:58 -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:subject:date; bh=RV5QTvMygwcM31S/hyrs6MnTkve28DlweGTrQchhxXo=; b=UJpdtPzQ4jg2bWxTTvLaBi+Ut8ibPGKpNFhDZh0iWTz3b+amhz6N+AZttgF2UwhDsT 0LBgQGCXwZMpWRgLy4vET4fOKKKgXxY1KuDJisX2XchJTyi2VCCX2dm68m0DAAvKGjC4 xIiTur2vx0OwVtk/WuhzSCK0dCMGsAVAL1CUqR69b/4FX/L7L9Ac2f05uDt/2u86QFT3 sZ1YamUl4cHshGvep6afoqIL2W3pcn/R7pZmOmD+ro7M2AzkNlTp3ADlUIg3hz9E6cPD /LU/ibYLRJEjq+u+M10jxNd1fjPNCkgQzBqOq14Kbt19kwHHkgk2aqR1DyBMN6VYb1BR uz3w== 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:subject:date; bh=RV5QTvMygwcM31S/hyrs6MnTkve28DlweGTrQchhxXo=; b=xaTOwQ+5AVn5EUtNFwD6p+HcgXq7uHvYntS7OpZpaEk28R9i9KRNexHrfsSmxiGi12 Oc6oF9GAhxwyBvm8s1PQAfUg22G+MJlX/tS8gdMkM3C3tPTMZqNlv8x7ofxjUXURWpGu Vyn1a4s+NPhBFpQtSeiAC3T+1YbSjNaOAE16QyRZAN1sLNHllDTeHUWy2j10rlyM3WG5 LP/M9dwaddfVd8ZQs3EocC4roZ1KitQVdoB2awDFVAWAtYr2GWv+9NPKkIIOZm1u+r+A R00maOgIbB/RPVBrUpChuR0OghMeop53aDEI43XJsf4AH+eDyREBctqOD3zF4PpbMPb2 JxTA== X-Gm-Message-State: ACgBeo12VYCwLZpDl1KRKopEoR/BGqPAMoJniow5giO5aekrR7b9HhY1 /yYwYn3WIMpqd7seTwdsdQsT9O4kKgY= X-Google-Smtp-Source: AA6agR7PXaXryyLZJx+eRIAfaY6wz+72tUpar4Sm/m5k7H+ezMzVzMxUtwtMAFDWbsTMvDkpBpYpems7Myc= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:b808:8d07:ab4a:554c]) (user=glider job=sendgmr) by 2002:aa7:cb87:0:b0:43b:e650:6036 with SMTP id r7-20020aa7cb87000000b0043be6506036mr44092076edt.350.1662380816223; Mon, 05 Sep 2022 05:26:56 -0700 (PDT) Date: Mon, 5 Sep 2022 14:24:51 +0200 In-Reply-To: <20220905122452.2258262-1-glider@google.com> Mime-Version: 1.0 References: <20220905122452.2258262-1-glider@google.com> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220905122452.2258262-44-glider@google.com> Subject: [PATCH v6 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 2.37.2.789.g6183377224-goog