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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C388DC6FA89 for ; Thu, 15 Sep 2022 15:12:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231193AbiIOPMm (ORCPT ); Thu, 15 Sep 2022 11:12:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231174AbiIOPKe (ORCPT ); Thu, 15 Sep 2022 11:10:34 -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 D5B1D6745E for ; Thu, 15 Sep 2022 08:06:34 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id m3-20020a056402430300b004512f6268dbso12395433edc.23 for ; Thu, 15 Sep 2022 08:06:34 -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=iXaNCvcxi4+6qBN7tuBlJCkmsRSEsjGSfB3SfZeymm0XXHHMDLmZS5purDypcnvs9C VSctdYvWkvSVdi7VcQVA/jXEY/asOBe0sjr7IHcePpfoj8cjbpyxzwMKoub6Mbfbj/u3 hdcX9KTPHnInN6LBhE2giGnIHgk4ArxBm8oNZQjrxTqj6l10QwAzi4OrPQG/dmLjnKeM uG5cIFQDMadCU8TrBcbzjSQl+YJOZv/uTPg3+I9KzZbdQlENHqwWW95ACZVZT9BbHfi5 bSJ9Yx8C2yAe2rvI5sDbQK6kyk//DTTYryP9Ky1nwr9gD2c+Xh/G4lERiS/g/gDCekau srrQ== 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=AclS1xQdY9pti+HXJ1oZhtkHfUv03Yg3K2mXsxWjt2k4LaqgDspXBgWtJ51Bnh//cq +cZcOhxzn4b10FBZrk2MLlTnE17tN8RCFNJY+8sXBsAVYQholCgW3r/0uY4BcF4Gwuzm PYI+B4tUOv3ODRFzdXovfGpRme92pUJO3scNYzgZ8xBJgE5hkhU5LUOWyIrwSZiHsvDM 1ljwj6bxfCGdM+LuknTrLsCuii8kKFNb3G5DezYpp3ltt2728xjewBYBgOmzVnVIWSrW hwQhJYSgO5+UrBrkSiu09dcrHkttZgv9L+Dxmrlfs0VrfndsiYIg0Z20qKFoHWqo2sSF 8A/g== X-Gm-Message-State: ACrzQf20CDQq59U3IRIrh3uORGvLCWSmQvl6DVVzIKvlPfOOwXCkcpg3 LT+9/q//XiDo3VGxTB5G2XS6v1WwNs4= X-Google-Smtp-Source: AMsMyM7bqtOZHqD5TLNiPJxrMbK30CsOC2CMkBTDAk4Y4jRe7EslTuJmgx6bYvgk5Yw3mmLO7YowFoN6c2M= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:686d:27b5:495:85b7]) (user=glider job=sendgmr) by 2002:a05:6402:4306:b0:451:8034:bcb6 with SMTP id m6-20020a056402430600b004518034bcb6mr291044edc.198.1663254393224; Thu, 15 Sep 2022 08:06:33 -0700 (PDT) Date: Thu, 15 Sep 2022 17:04:16 +0200 In-Reply-To: <20220915150417.722975-1-glider@google.com> Mime-Version: 1.0 References: <20220915150417.722975-1-glider@google.com> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220915150417.722975-43-glider@google.com> Subject: [PATCH v7 42/43] 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 Biggers , 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 , Stephen Rothwell , 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 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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/Ie300c21bbe9dea69a730745bd3c6d2720953bf41 --- 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, loff_t size) struct address_space *mapping = inode->i_mapping; const struct address_space_operations *aops = mapping->a_ops; struct page *page; - void *fsdata; + void *fsdata = NULL; int err; err = 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 = mapping->a_ops; unsigned int blocksize = i_blocksize(inode); struct page *page; - void *fsdata; + void *fsdata = 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 *symname, int len) const struct address_space_operations *aops = mapping->a_ops; bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS); struct page *page; - void *fsdata; + void *fsdata = NULL; int err; unsigned int flags; 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, struct 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 = NULL; offset = (pos & (PAGE_SIZE - 1)); bytes = min_t(unsigned long, PAGE_SIZE - offset, -- 2.37.2.789.g6183377224-goog