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_comp_prepare() only initializes
acomp_ctx fields with the mutex held, after performing all allocations
before holding the mutex.
Opportunistically, move the NULL check on acomp_ctx so that it takes place
before the mutex dereference.
                
            Metrics
Affected Vendors & Products
References
        History
                    Tue, 28 Oct 2025 19:15:00 +0000
| Type | Values Removed | Values Added | 
|---|---|---|
| First Time appeared | 
        
        Linux
         Linux linux Kernel  | 
|
| Weaknesses | CWE-667 | |
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.13:-:*:*:*:*:*:*  | 
|
| Vendors & Products | 
        
        Linux
         Linux linux Kernel  | 
Fri, 25 Apr 2025 16:00:00 +0000
| Type | Values Removed | Values Added | 
|---|---|---|
| Weaknesses | CWE-833 | 
Sat, 19 Apr 2025 02:00:00 +0000
| Type | Values Removed | Values Added | 
|---|---|---|
| References | 
         | |
| Metrics | 
        
        
        threat_severity
         
  | 
    
        
        cvssV3_1
         
 
  | 
Wed, 16 Apr 2025 14:30:00 +0000
| Type | Values Removed | Values Added | 
|---|---|---|
| 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_comp_prepare() only initializes acomp_ctx fields with the mutex held, after performing all allocations before holding the mutex. Opportunistically, move the NULL check on acomp_ctx so that it takes place before the mutex dereference. | |
| Title | mm: zswap: fix crypto_free_acomp() deadlock in zswap_cpu_comp_dead() | |
| References | 
         | 
Status: PUBLISHED
Assigner: Linux
Published: 2025-04-16T14:11:50.625Z
Updated: 2025-05-26T05:16:57.089Z
Reserved: 2024-12-29T08:45:45.808Z
Link: CVE-2025-22030
No data.
Status : Analyzed
Published: 2025-04-16T15:15:55.607
Modified: 2025-10-28T19:05:41.203
Link: CVE-2025-22030