6.12-stable review patch. If anyone has any objections, please let me know.
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From: Dennis Lam dennis.lamerice@gmail.com
commit 5f3fd772d152229d94602bca243fbb658068a597 upstream.
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 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.
[akpm@linux-foundation.org: coding-style cleanups] 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.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 +++ b/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 +++ b/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; }