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 2C08A3C1F for ; Mon, 30 Jun 2025 01:26:49 +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=1751246813; cv=none; b=f4UspqpBzVrrsIsrjTZ0miwZbpcoP/6vUzG80+FmxUZYQ4NTx45fkwWG7pT1EqVWLDWohCzvfpZgu++TkqJ4L+pBov3VOJSIyUFgqEMxgrWBmRPJN9dHqkpm1SZ9mtvZmaLMpS0PTHB4DNfMCwemxXYJymn4Yl2GZ2lbf3aydas= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751246813; c=relaxed/simple; bh=OaGhSavxgehz1kxRS4bQjLJGrxCBBHISqRgUIQdbHyQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=STCC1qDLFJ4mZlFmZlxrYzDlLKKYMYyLYA0dzxvqi0lMiMds09roZfbiBoj1HNwshaI0NCTMd9taWK57Yv2H0QnjM8MRCkRkDtKNtM3dHm9MAwyVc46j1szx5VoH4GlrnSE1eRVGgWfTui41rQIAmv5pdOm13o/OAmomNpmtoeU= 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=EUckvlZm; 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="EUckvlZm" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1751246802; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=fq6cIu+dmFZv0xYGNfLmiRHpzV744XSYtX95GIPUPHU=; b=EUckvlZmsi8J9l1hxej5/6Z6f4e8QBJLFf/fqXbr1+U2bEfRHnPD8agRinlJveb+9/lWgiRsFBI36Y0MbAaT+OYgWiG+DjlCZgdwk1jF5Z1rQmlnrGecOQsqk5WrDPCWgF66SPcYUUcfbZ0xgGyoewgu9Y9R/EM5X4k62Ve1adk= Received: from 30.221.128.206(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0Wg2L7Fz_1751246801 cluster:ay36) by smtp.aliyun-inc.com; Mon, 30 Jun 2025 09:26:41 +0800 Message-ID: Date: Mon, 30 Jun 2025 09:26:40 +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: Avoid NULL pointer dereference in dx_dir_lookup_rec() To: Ivan Pravdin , mark@fasheh.com, jlbec@evilplan.org, ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org Cc: syzbot+20282c1b2184a857ac4c@syzkaller.appspotmail.com References: <20250627023830.150291-1-ipravdin.official@gmail.com> From: Joseph Qi In-Reply-To: <20250627023830.150291-1-ipravdin.official@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 2025/6/27 10:38, Ivan Pravdin wrote: > When a directory entry is not found, ocfs2_dx_dir_lookup_rec() prints an > error message that unconditionally dereferences the 'rec' pointer. > However, if 'rec' is NULL, this leads to a NULL pointer dereference and > a kernel panic. > This looks possible, but syzbot reports slab-out-of-bounds Read in ocfs2_dx_dir_lookup_rec(), not NULL pointer dereference. So I think it is because it construct a malicious image and set a wrong l_recs, then access this damaged l_recs. Thanks, Joseph > Add an explicit check for a NULL 'rec' and use an alternate error > message in that case to avoid unsafe access. > > Reported-by: syzbot+20282c1b2184a857ac4c@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/67483b75.050a0220.253251.007c.GAE@google.com/T/ > Signed-off-by: Ivan Pravdin > --- > fs/ocfs2/dir.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c > index 7799f4d16ce9..dccf0349e523 100644 > --- a/fs/ocfs2/dir.c > +++ b/fs/ocfs2/dir.c > @@ -809,11 +809,17 @@ static int ocfs2_dx_dir_lookup_rec(struct inode *inode, > } > > if (!found) { > - ret = ocfs2_error(inode->i_sb, > - "Inode %lu has bad extent record (%u, %u, 0) in btree\n", > - inode->i_ino, > - le32_to_cpu(rec->e_cpos), > - ocfs2_rec_clusters(el, rec)); > + if (rec) { > + ret = ocfs2_error(inode->i_sb, > + "Inode %lu has bad extent record (%u, %u, 0) in btree\n", > + inode->i_ino, > + le32_to_cpu(rec->e_cpos), > + ocfs2_rec_clusters(el, rec)); > + } else { > + ret = ocfs2_error(inode->i_sb, > + "Inode %lu has no extent records in btree\n", > + inode->i_ino); > + } > goto out; > } >