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

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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: 8f9e8f5fcc ("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>
This commit is contained in:
Dennis Lam 2024-12-17 21:39:25 -05:00 committed by Andrew Morton
parent a45c68ddb3
commit 1aefbedee7
2 changed files with 2 additions and 1 deletions
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2
fs/ocfs2/quota_global.c
View File

@ -893,7 +893,7 @@ 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_active(sb, type)){
status = -ESRCH;
goto out;
}

1
fs/ocfs2/quota_local.c
View File

@ -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;
}