bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel
The following race is possible between bpf_timer_cancel_and_free
and bpf_timer_cancel. It will lead a UAF on the timer->timer.
bpf_timer_cancel();
spin_lock();
t = timer->time;
spin_unlock();
bpf_timer_cancel_and_free();
spin_lock();
t = timer->timer;
timer->timer = NULL;
spin_unlock();
hrtimer_cancel(&t->timer);
kfree(t);
/* UAF on t */
hrtimer_cancel(&t->timer);
In bpf_timer_cancel_and_free, this patch frees the timer->timer
after a rcu grace period. This requires a rcu_head addition
to the "struct bpf_hrtimer". Another kfree(t) happens in bpf_timer_init,
this does not need a kfree_rcu because it is still under the
spin_lock and timer->timer has not been visible by others yet.
In bpf_timer_cancel, rcu_read_lock() is added because this helper
can be used in a non rcu critical section context (e.g. from
a sleepable bpf prog). Other timer->timer usages in helpers.c
have been audited, bpf_timer_cancel() is the only place where
timer->timer is used outside of the spin_lock.
Another solution considered is to mark a t->flag in bpf_timer_cancel
and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free,
it busy waits for the flag to be cleared before kfree(t). This patch
goes with a straight forward solution and frees timer->timer after
a rcu grace period.
Analysis and contextual insights are available on OpenCVE Cloud.
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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| Source | ID | Title |
|---|---|---|
Debian DSA |
DSA-5658-1 | linux security update |
Ubuntu USN |
USN-6820-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-6820-2 | Linux kernel (NVIDIA) vulnerabilities |
Ubuntu USN |
USN-6821-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-6821-2 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-6821-3 | Linux kernel (AWS) vulnerabilities |
Ubuntu USN |
USN-6821-4 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-6828-1 | Linux kernel (Intel IoTG) vulnerabilities |
Ubuntu USN |
USN-6871-1 | Linux kernel (HWE) vulnerabilities |
Ubuntu USN |
USN-6892-1 | Linux kernel (IBM) vulnerabilities |
Ubuntu USN |
USN-6919-1 | Linux kernel vulnerabilities |
Fri, 04 Apr 2025 15:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.8:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.8:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.8:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.8:rc4:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.8:rc5:*:*:*:*:*:* |
|
| Vendors & Products |
Linux
Linux linux Kernel |
Wed, 07 Aug 2024 22:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| CPEs | cpe:/a:redhat:rhel_eus:9.2 |
Wed, 07 Aug 2024 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Redhat rhel Eus
|
|
| CPEs | cpe:/a:redhat:rhel_eus:9.2::nfv | |
| Vendors & Products |
Redhat rhel Eus
|
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-05-11T20:03:10.783Z
Reserved: 2024-02-19T14:20:24.166Z
Link: CVE-2024-26737
Updated: 2024-08-02T00:14:13.230Z
Status : Analyzed
Published: 2024-04-03T17:15:51.243
Modified: 2025-04-04T14:34:28.903
Link: CVE-2024-26737
OpenCVE Enrichment
No data.
Debian DSA
Ubuntu USN