Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv
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.
[[email protected]: coding-style cleanups]
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , Oracle Linux 7 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS
- Affected packages:
- linux @ 4.15.0 (+8 more)
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv
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.
[[email protected]: coding-style cleanups]