CVE-2024-26737
In the Linux kernel, the following vulnerability has been resolved: 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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.25%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: 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.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.25% probability · 17th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-416
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/0281b919e175bb9c3128bd3872ac2903e9436e3fPatch
- https://git.kernel.org/stable/c/5268bb02107b9eedfdcd51db75b407d10043368cPatch
- https://git.kernel.org/stable/c/7d80a9e745fa5b47da3bca001f186c02485c7c33Patch
- https://git.kernel.org/stable/c/8327ed12e8ebc5436bfaa1786c49988894f9c8a6Patch
- https://git.kernel.org/stable/c/addf5e297e6cbf5341f9c07720693ca9ba0057b5Patch
- https://git.kernel.org/stable/c/0281b919e175bb9c3128bd3872ac2903e9436e3fPatch
- https://git.kernel.org/stable/c/5268bb02107b9eedfdcd51db75b407d10043368cPatch
- https://git.kernel.org/stable/c/7d80a9e745fa5b47da3bca001f186c02485c7c33Patch
- https://git.kernel.org/stable/c/8327ed12e8ebc5436bfaa1786c49988894f9c8a6Patch
- https://git.kernel.org/stable/c/addf5e297e6cbf5341f9c07720693ca9ba0057b5Patch
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.