CVE-2026-46121

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/sysfs-schemes: protect memcg_path kfree() with damon_sysfs_lock

Patch series mm/damon/sysfs-schemes: fix use-after-free for [memcg_]path.

Reads of memcg_path and path files in DAMON sysfs interface could race with their writes, results in use-after-free. Fix those.

This patch (of 2):

damon_sysfs_scheme_filter->mmecg_path can be read and written by users, via DAMON sysfs memcg_path file. It can also be indirectly read, for the parameters {on,off}line committing to DAMON. The reads for parameters committing are protected by damon_sysfs_lock to avoid the sysfs files being destroyed while any of the parameters are being read. But the user-driven direct reads and writes are not protected by any lock, while the write is deallocating the memcg_path-pointing buffer. As a result, the readers could read the already freed buffer (user-after-free). Note that the user-reads dont race when the same open file is used by the writer, due to kernfss open file locking. Nonetheless, doing the reads and writes with separate open files would be common. Fix it by protecting both the user-direct reads and writes with damon_sysfs_lock.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/1e68eb96e8beb1abefd12dd22c5637795d8a877e
• https://git.kernel.org/stable/c/b1e9f2d5870776347edef927f9bb3ea19b8e3abb
• https://git.kernel.org/stable/c/baecc45ad60e621ef14d6c1e7f41ef36bbfdf910
• https://git.kernel.org/stable/c/c88802d0e8edd14b6cd2daf3000f99adbc4c85c5
• https://git.kernel.org/stable/c/eafd6f5372d29b0dd213799b92c2c9c7ad31d7da