CVE-2025-22124 md/md-bitmap: fix wrong bitmap_limit for clustermd when write sb
A logic error in the Linux kernel's clustermd bitmap handling causes a hang during superblock writes, leading to denial of service in clustered environments.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-22124?
CVE-2025-22124 is a high-severity denial of service vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
md/md-bitmap: fix wrong bitmap_limit for clustermd when write sb
In clustermd, separate write-intent-bitmaps are used for each cluster node:
0 4k 8k 12k ------------------------------------------------------------------- | idle | md super | bm super [0] + bits | | bm bits[0, contd] | bm super[1] + bits | bm bits[1, contd] | | bm super[2] + bits | bm bits [2, contd] | bm super[3] + bits | | bm bits [3, contd] | | |
So in node 1, pg_index in __write_sb_page() could equal to bitmap->storage.file_pages. Then bitmap_limit will be calculated to 0. md_super_write() will be called with 0 size. That means the first 4k sb area of node 1 will never be updated through filemap_write_page(). This bug causes hang of mdadm/clustermd_tests/01r1_Grow_resize.
Here use (pg_index % bitmap->storage.file_pages) to make calculation of bitmap_limit correct.
Which versions are affected by CVE-2025-22124?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-22124?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-22124 being exploited?
There is no known exploitation of CVE-2025-22124 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-69616, BELL-CVE-2025-22124, DEBIAN-CVE-2025-22124, GHSA-48f7-49jv-jj2v, ROOT-OS-DEBIAN-13-CVE-2025-22124, ROOT-OS-UBUNTU-2204-CVE-2025-22124 and 2 more.