Description

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 it's not safe as well. Refer to md_seq_show(), also factor
out a helper mddev_put_locked() to fix this problem.

Classification

CVE ID: CVE-2025-22126

Affected Products

Vendor: Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 4.75% (scored less or equal to compared to others)

EPSS Date: 2025-04-25 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-22126
https://git.kernel.org/stable/c/5462544ccbad3fc938a71b01fa5bd3a0dc2b750a
https://git.kernel.org/stable/c/8542870237c3a48ff049b6c5df5f50c8728284fa

Timeline