In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_api: use RCU with deferred freeing for action lifecycle
When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
race with an associated action.
Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:
0: mutex_lock() <-- holds the idr lock
0: rcu_read_lock()
0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)
0: mutex_unlock() <-- releases the idr lock
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index) <-- Action removed from IDR
1: mutex_unlock() <-- mutex released allowing us to delete the action
1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory
This patch fixes the race condition between NEWTFILTER and DELFILTER by
adding struct rcu_head to tc_action used in the deferral and introducing a
call_rcu() in the delete path to defer the final kfree().
Note: this is a revert of commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu")
but also modernization/simplification to directly use kfree_rcu().
Let's illustrate the new restored code path:
0: rcu_read_lock()
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index)
1: mutex_unlock()
1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period
0: p = idr_find(idr, index)
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0
1: rcu_read_unlock() <-- release so freeing can run after grace period
After CPU1 calls idr_remove(), the object is no longer reachable through the IDR.
CPU0's subsequent idr_find() will return NULL, and even if it still held a
stale pointer, the immediate kfree() is now deferred until after the RCU grace
period, so no UAF can occur.
References
Configurations
Configuration 1 (hide)
|
History
08 Jul 2026, 04:02
| Type | Values Removed | Values Added |
|---|---|---|
| First Time |
Linux linux Kernel
Linux |
|
| CWE | CWE-416 | |
| CPE | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc5:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.1:rc6:*:*:*:*:*:* |
|
| References | () https://git.kernel.org/stable/c/18af5d2ef0c4f65787fd1280c8b23286b9f2a835 - Patch | |
| References | () https://git.kernel.org/stable/c/1f1b98fea6b9ea30507d0f2fbff6750292d097e2 - Patch | |
| References | () https://git.kernel.org/stable/c/5057e1aca011e51ef51498c940ef96f3d3e8a305 - Patch | |
| References | () https://git.kernel.org/stable/c/5dd51e09020c65aa53cf128e5e3517cd53b3c113 - Patch | |
| References | () https://git.kernel.org/stable/c/8b136f18ac4b2ace5aaad3305b3f8a5d8165a009 - Patch | |
| References | () https://git.kernel.org/stable/c/91d105d2cbe002f9c7b43a6183adedc37e1da1f7 - Patch | |
| References | () https://git.kernel.org/stable/c/98b2e40879abf0245be5a5b7af69e0f6ff524ac3 - Patch | |
| References | () https://git.kernel.org/stable/c/b60e9391142e983fab2be53497aa8f71fdd09cd5 - Patch |
28 Jun 2026, 08:16
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.8 |
25 Jun 2026, 09:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-06-25 09:16
Updated : 2026-07-08 04:02
NVD link : CVE-2026-53264
Mitre link : CVE-2026-53264
CVE.ORG link : CVE-2026-53264
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free