From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-124.freemail.mail.aliyun.com (out30-124.freemail.mail.aliyun.com [115.124.30.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3D3CF158DD0 for ; Fri, 1 Nov 2024 12:53:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730465612; cv=none; b=q+2QpvHgZSMlvVKl4VmHOYAL/oiMDrvKa/vxOf01TS0l2jL1pcJtY+6lBqiTtEhMVygpyRwwrU8WDO2U2RxwnE/H8ebocjUm6iH9wzFqS2oXRuElYNFUsKnx9HF3pJihqOM+50g0t+KykVowsLxOri86j0Ts7e+6pRBciRCs5Hc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730465612; c=relaxed/simple; bh=dRt8Wt33a+gJr4pdbe3BFWFJKSsT0SiGi9tnumU4C9o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=b90tKndpnvSNYiieHvk1jSmEGpWqmuURV2w69yO2cUZDLjj4ICF9Cj1p0NMiOQGSM1AbEkHe/mvxQqz1as+RY9LWxjcTjWGurHDZSvyFrCcZoS9YxiVoPoeNQeYx++VCVuqWLDQsuebWiE8wYbYCEBXPelKFrbgPLgFwpFJCYvo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=Rw0Npdsz; arc=none smtp.client-ip=115.124.30.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="Rw0Npdsz" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1730465600; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=YZOjb27QH5lTJMffOv2w8pz522mkN3F8THfiuw78qFY=; b=Rw0NpdszPgqKAhEg3o95OhfS6NltHP2f3wIWrWD/RiMz1ejG3YqWG7xwNXgP5PEKZyhkgazR+zn0DT3aaFoZt5BcQrhrC6yRzDZTRPJQGAJ/vSmLODCJy2w04GnttuQZbuhzDCp2rFLS+mq1YrCI+EUaDLMZYu/nbXtef544JrQ= Received: from 30.221.65.110(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0WISGh2f_1730465599 cluster:ay36) by smtp.aliyun-inc.com; Fri, 01 Nov 2024 20:53:20 +0800 Message-ID: Date: Fri, 1 Nov 2024 20:53:18 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ocfs2: remove entry once instead of null-ptr-dereference in ocfs2_xa_remove() To: Andrew Kanner , mark@fasheh.com, jlbec@evilplan.org Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com References: <20241029224304.2169092-2-andrew.kanner@gmail.com> Content-Language: en-US From: Joseph Qi In-Reply-To: <20241029224304.2169092-2-andrew.kanner@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/30/24 6:43 AM, Andrew Kanner wrote: > Syzkaller is able to provoke null-ptr-dereference in ocfs2_xa_remove(): > > [ 57.319872] (a.out,1161,7):ocfs2_xa_remove:2028 ERROR: status = -12 > [ 57.320420] (a.out,1161,7):ocfs2_xa_cleanup_value_truncate:1999 ERROR: Partial truncate while removing xattr overlay.upper. Leaking 1 clusters and removing the entry > [ 57.321727] BUG: kernel NULL pointer dereference, address: 0000000000000004 > [...] > [ 57.325727] RIP: 0010:ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 > [...] > [ 57.331328] Call Trace: > [ 57.331477] > [...] > [ 57.333511] ? do_user_addr_fault+0x3e5/0x740 > [ 57.333778] ? exc_page_fault+0x70/0x170 > [ 57.334016] ? asm_exc_page_fault+0x2b/0x30 > [ 57.334263] ? __pfx_ocfs2_xa_block_wipe_namevalue+0x10/0x10 > [ 57.334596] ? ocfs2_xa_block_wipe_namevalue+0x2a/0xc0 > [ 57.334913] ocfs2_xa_remove_entry+0x23/0xc0 > [ 57.335164] ocfs2_xa_set+0x704/0xcf0 > [ 57.335381] ? _raw_spin_unlock+0x1a/0x40 > [ 57.335620] ? ocfs2_inode_cache_unlock+0x16/0x20 > [ 57.335915] ? trace_preempt_on+0x1e/0x70 > [ 57.336153] ? start_this_handle+0x16c/0x500 > [ 57.336410] ? preempt_count_sub+0x50/0x80 > [ 57.336656] ? _raw_read_unlock+0x20/0x40 > [ 57.336906] ? start_this_handle+0x16c/0x500 > [ 57.337162] ocfs2_xattr_block_set+0xa6/0x1e0 > [ 57.337424] __ocfs2_xattr_set_handle+0x1fd/0x5d0 > [ 57.337706] ? ocfs2_start_trans+0x13d/0x290 > [ 57.337971] ocfs2_xattr_set+0xb13/0xfb0 > [ 57.338207] ? dput+0x46/0x1c0 > [ 57.338393] ocfs2_xattr_trusted_set+0x28/0x30 > [ 57.338665] ? ocfs2_xattr_trusted_set+0x28/0x30 > [ 57.338948] __vfs_removexattr+0x92/0xc0 > [ 57.339182] __vfs_removexattr_locked+0xd5/0x190 > [ 57.339456] ? preempt_count_sub+0x50/0x80 > [ 57.339705] vfs_removexattr+0x5f/0x100 > [...] > > Reproducer uses faultinject facility to fail ocfs2_xa_remove() -> > ocfs2_xa_value_truncate() with -ENOMEM. > > In this case the comment mentions that we can return 0 if > ocfs2_xa_cleanup_value_truncate() is going to wipe the entry > anyway. But the following 'rc' check is wrong and execution flow do > 'ocfs2_xa_remove_entry(loc);' twice: > * 1st: in ocfs2_xa_cleanup_value_truncate(); > * 2nd: returning back to ocfs2_xa_remove() instead of going to 'out'. > > Fix this by skipping the 2nd removal of the same entry and making > syzkaller repro happy. > > Cc: stable@vger.kernel.org > Fixes: 399ff3a748cf ("ocfs2: Handle errors while setting external xattr values.") > Reported-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/671e13ab.050a0220.2b8c0f.01d0.GAE@google.com/T/ > Tested-by: syzbot+386ce9e60fa1b18aac5b@syzkaller.appspotmail.com > Signed-off-by: Andrew Kanner > --- > fs/ocfs2/xattr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c > index dd0a05365e79..5bc4d660e15a 100644 > --- a/fs/ocfs2/xattr.c > +++ b/fs/ocfs2/xattr.c > @@ -2036,7 +2036,7 @@ static int ocfs2_xa_remove(struct ocfs2_xa_loc *loc, > rc = 0; > ocfs2_xa_cleanup_value_truncate(loc, "removing", > orig_clusters); > - if (rc) > + if (rc == 0) Seems in this case, we have to ignore rc and directly goto out? Thanks, Joseph > goto out; > } > }