CVE-2024-26737 Affecting cluster-md-kmp-default package, versions <6.4.0-150600.23.7.3
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Test your applications- Snyk ID SNYK-SLES156-CLUSTERMDKMPDEFAULT-7712987
- published 20 Aug 2024
- disclosed 25 Jun 2024
Introduced: 25 Jun 2024
CVE-2024-26737 Open this link in a new tabHow to fix?
Upgrade SLES:15.6 cluster-md-kmp-default to version 6.4.0-150600.23.7.3 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream cluster-md-kmp-default package and not the cluster-md-kmp-default package as distributed by SLES.
See How to fix? for SLES:15.6 relevant fixed versions and status.
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.
References
- https://www.suse.com/security/cve/CVE-2024-26737.html
- https://bugzilla.suse.com/1222557
- https://git.kernel.org/stable/c/0281b919e175bb9c3128bd3872ac2903e9436e3f
- https://git.kernel.org/stable/c/5268bb02107b9eedfdcd51db75b407d10043368c
- https://git.kernel.org/stable/c/7d80a9e745fa5b47da3bca001f186c02485c7c33
- https://git.kernel.org/stable/c/8327ed12e8ebc5436bfaa1786c49988894f9c8a6
- https://git.kernel.org/stable/c/addf5e297e6cbf5341f9c07720693ca9ba0057b5