+ ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv.patch added to mm-nonmm-unstable branch

+ ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Dennis Lam <dennis.lamerice@gmail.com>
Subject: ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv
Date: Tue, 17 Dec 2024 21:39:25 -0500

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.

Link: https://lkml.kernel.org/r/20241218023924.22821-2-dennis.lamerice@gmail.com
Fixes: 8f9e8f5fcc05 ("ocfs2: Fix Q_GETNEXTQUOTA for filesystem without quotas")
Signed-off-by: Dennis Lam <dennis.lamerice@gmail.com>
Reported-by: syzbot+d173bf8a5a7faeede34c@syzkaller.appspotmail.com
Tested-by: syzbot+d173bf8a5a7faeede34c@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6731d26f.050a0220.1fb99c.014b.GAE@google.com/T/
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/quota_global.c |    2 +-
 fs/ocfs2/quota_local.c  |    1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ocfs2/quota_global.c~ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv
+++ a/fs/ocfs2/quota_global.c
@@ -893,7 +893,7 @@ static int ocfs2_get_next_id(struct supe
 	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_active(sb, type)){
 		status = -ESRCH;
 		goto out;
 	}
--- a/fs/ocfs2/quota_local.c~ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv
+++ a/fs/ocfs2/quota_local.c
@@ -867,6 +867,7 @@ out:
 	brelse(oinfo->dqi_libh);
 	brelse(oinfo->dqi_lqi_bh);
 	kfree(oinfo);
+	info->dqi_priv = NULL;
 	return status;
 }
 
_

Patches currently in -mm which might be from dennis.lamerice@gmail.com are

ocfs2-fix-slab-use-after-free-due-to-dangling-pointer-dqi_priv.patch