CVE-2025-22126

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

md: fix mddev uaf while iterating all_mddevs list

While iterating all_mddevs list from md_notify_reboot() and md_exit(), list_for_each_entry_safe is used, and this can race with deletint the next mddev, causing UAF:

t1: spin_lock //list_for_each_entry_safe(mddev, n, …) mddev_get(mddev1) // assume mddev2 is the next entry spin_unlock t2: //remove mddev2 … mddev_free spin_lock list_del spin_unlock kfree(mddev2) mddev_put(mddev1) spin_lock //continue dereference mddev2->all_mddevs

The old helper for_each_mddev() actually grab the reference of mddev2 while holding the lock, to prevent from being freed. This problem can be fixed the same way, however, the code will be complex.

Hence switch to use list_for_each_entry, in this case mddev_put() can free the mddev1 and its not safe as well. Refer to md_seq_show(), also factor out a helper mddev_put_locked() to fix this problem.

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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.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/5462544ccbad3fc938a71b01fa5bd3a0dc2b750a
• https://git.kernel.org/stable/c/8542870237c3a48ff049b6c5df5f50c8728284fa
• https://git.kernel.org/stable/c/ca9f84de76723b358dfc0606668efdca54afc2e5
• https://git.kernel.org/stable/c/d69a23d8e925f8052d657652a6875ec2712c7e33
• https://git.kernel.org/stable/c/e2a9f73ee408a460f4c9dfe03b4741d6b11652b8
• https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html