From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-112.freemail.mail.aliyun.com (out30-112.freemail.mail.aliyun.com [115.124.30.112]) (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 1E22A1F12FA for ; Tue, 17 Dec 2024 12:35:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.112 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734438958; cv=none; b=TGJJP1EDaUKPuev+C/9+MgUO3b6ZOr0jECvZMT95X6M5vvcLXh0SVWMkLNBA/uzwnxtuDJpUmasf9lHmiuA4dVTMQC2UK7xJDJwLWF0K32JhmYJQ02KynIUrHarXKsrqkRtZL3EzqyoorDoWIw33V03nJj2zJ+GatPpqh5nVEoI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734438958; c=relaxed/simple; bh=sqKkRZksVUeZVFhDKfPmfafbSD6yBYhW5Q/1vVAv5CI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ToHRyrA0lHVPkx1MTy7mOf94la97DUbytfQ7SbRKD9GcsB+C76FkFuBdVE5ihaixrqmEidOeqe1CwTkx2ttgLew93tNJZWQwmQibNF2jiRFy7MzVwpR7tWOlCeNYIjKrXmQjAP5zanq4nZ2kbRy2THtGEkbqTw4IAcnXMeE8/aU= 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=TwAE3ji0; arc=none smtp.client-ip=115.124.30.112 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="TwAE3ji0" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1734438946; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=cxpXJZRKPdL3JtCadcEw4asuX7c+VcjU2sev26XlNqA=; b=TwAE3ji0lApqbi2Uk7tvhFQ0nf1EA0chyd1hPQyoOi1VR5bPlkBXzs8Up5xDZyjWP2zAqMFvB5zKf/P258c4FsoBzR4suvykKNALgxdCqwS+63xnUN/FIcMa40r7pLccY2ZGnFdorOrFAg86zNU5ZOV6mdxmZd9vdqwqBxN06lA= Received: from 30.221.145.236(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0WLjD.Zq_1734438945 cluster:ay36) by smtp.aliyun-inc.com; Tue, 17 Dec 2024 20:35:46 +0800 Message-ID: Date: Tue, 17 Dec 2024 20:35:44 +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: fix slab-use-after-free due to dangling pointer dqi_priv To: Dennis Lam , mark@fasheh.com, jlbec@evilplan.org Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, syzbot+d173bf8a5a7faeede34c@syzkaller.appspotmail.com References: <20241215035828.106936-2-dennis.lamerice@gmail.com> From: Joseph Qi In-Reply-To: <20241215035828.106936-2-dennis.lamerice@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2024/12/15 11:58, Dennis Lam wrote: > When mounting ocfs2 and then remounting it as read-only, a > slab-use-after-free occurs after the user uses a syscall to > quota_getnextquota. Specifically, sb_dqinfo(sb, type)->dqi_priv is the > dangling pointer. > > During the remounting process, the pointer dqi_priv is freed but is > never set as null leaving it to to be accessed. Additionally, the > read-only option for remounting sets the DQUOT_SUSPENDED flag instead of > setting the DQUOT_USAGE_ENABLED flags. Moreover, later in the process of > getting the next quota, the function ocfs2_get_next_id is called and > only checks the quota usage flags and not the quota suspended flags. > > To fix this, I set dqi_priv to null when it is freed after remounting > with read-only and put a check for DQUOT_SUSPENDED in ocfs2_get_next_id. > > Signed-off-by: Dennis Lam > Reported-by: syzbot+d173bf8a5a7faeede34c@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/6731d26f.050a0220.1fb99c.014b.GAE@google.com/T/ > --- > fs/ocfs2/quota_global.c | 3 ++- > fs/ocfs2/quota_local.c | 1 + > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c > index 2b0daced98eb..c6d38340d6d4 100644 > --- a/fs/ocfs2/quota_global.c > +++ b/fs/ocfs2/quota_global.c > @@ -893,7 +893,8 @@ static int ocfs2_get_next_id(struct super_block *sb, struct kqid *qid) > int status = 0; > > trace_ocfs2_get_next_id(from_kqid(&init_user_ns, *qid), type); > - if (!sb_has_quota_loaded(sb, type)) { > + if (!sb_has_quota_loaded(sb, type) || > + sb_dqopt(sb)->flags & DQUOT_SUSPENDED) { Looks reasonable. We can just use !sb_has_quota_active() instead. Thanks, Joseph > status = -ESRCH; > goto out; > } > diff --git a/fs/ocfs2/quota_local.c b/fs/ocfs2/quota_local.c > index 73d3367c533b..2956d888c131 100644 > --- a/fs/ocfs2/quota_local.c > +++ b/fs/ocfs2/quota_local.c > @@ -867,6 +867,7 @@ static int ocfs2_local_free_info(struct super_block *sb, int type) > brelse(oinfo->dqi_libh); > brelse(oinfo->dqi_lqi_bh); > kfree(oinfo); > + info->dqi_priv = NULL; > return status; > } >