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.
History

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

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2024-04-03T17:00:23.414Z

Updated: 2024-08-02T00:14:13.230Z

Reserved: 2024-02-19T14:20:24.166Z

Link: CVE-2024-26737

cve-icon Vulnrichment

Updated: 2024-05-23T19:01:21.859Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2024-04-03T17:15:51.243

Modified: 2024-04-03T17:24:18.150

Link: CVE-2024-26737

cve-icon Redhat

Severity : Moderate

Publid Date: 2024-04-03T00:00:00Z

Links: CVE-2024-26737 - Bugzilla