Description

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

mm: zswap: fix crypto_free_acomp() deadlock in zswap_cpu_comp_dead()

Currently, zswap_cpu_comp_dead() calls crypto_free_acomp() while holding
the per-CPU acomp_ctx mutex. crypto_free_acomp() then holds scomp_lock
(through crypto_exit_scomp_ops_async()).

On the other hand, crypto_alloc_acomp_node() holds the scomp_lock (through
crypto_scomp_init_tfm()), and then allocates memory. If the allocation
results in reclaim, we may attempt to hold the per-CPU acomp_ctx mutex.

The above dependencies can cause an ABBA deadlock. For example in the
following scenario:

(1) Task A running on CPU #1:
crypto_alloc_acomp_node()
Holds scomp_lock
Enters reclaim
Reads per_cpu_ptr(pool->acomp_ctx, 1)

(2) Task A is descheduled

(3) CPU #1 goes offline
zswap_cpu_comp_dead(CPU #1)
Holds per_cpu_ptr(pool->acomp_ctx, 1))
Calls crypto_free_acomp()
Waits for scomp_lock

(4) Task A running on CPU #2:
Waits for per_cpu_ptr(pool->acomp_ctx, 1) // Read on CPU #1
DEADLOCK

Since there is no requirement to call crypto_free_acomp() with the per-CPU
acomp_ctx mutex held in zswap_cpu_comp_dead(), move it after the mutex is
unlocked. Also move the acomp_request_free() and kfree() calls for
consistency and to avoid any potential sublte locking dependencies in the
future.

With this, only setting acomp_ctx fields to NULL occurs with the mutex
held. This is similar to how zswap_cpu...

Classification

CVE ID: CVE-2025-22030

Affected Products

Vendor: Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 2.91% (scored less or equal to compared to others)

EPSS Date: 2025-04-20 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-22030
https://git.kernel.org/stable/c/747e3eec1d7d124ea90ed3d7b85369df8b4e36d2
https://git.kernel.org/stable/c/a8d18000e9d2d97aaf105f5f9b3b0e8a6fbf8b96
https://git.kernel.org/stable/c/717d9c35deff6c33235693171bacbb03e9643fa4
https://git.kernel.org/stable/c/c11bcbc0a517acf69282c8225059b2a8ac5fe628

Timeline