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Amazon Linux 2023: CVE-2024-26737: Important priority package update for kernel

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Amazon Linux 2023: CVE-2024-26737: Important priority package update for kernel

Severity
5
CVSS
(AV:L/AC:L/Au:S/C:N/I:N/A:C)
Published
04/03/2024
Created
02/14/2025
Added
02/14/2025
Modified
02/14/2025

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. A use-after-free flaw was found in the Linux kernel’s BPF functionality. This flaw allows a local user to crash the system.

Solution(s)

  • amazon-linux-2023-upgrade-bpftool
  • amazon-linux-2023-upgrade-bpftool-debuginfo
  • amazon-linux-2023-upgrade-kernel
  • amazon-linux-2023-upgrade-kernel-debuginfo
  • amazon-linux-2023-upgrade-kernel-debuginfo-common-aarch64
  • amazon-linux-2023-upgrade-kernel-debuginfo-common-x86-64
  • amazon-linux-2023-upgrade-kernel-devel
  • amazon-linux-2023-upgrade-kernel-headers
  • amazon-linux-2023-upgrade-kernel-libbpf
  • amazon-linux-2023-upgrade-kernel-libbpf-devel
  • amazon-linux-2023-upgrade-kernel-libbpf-static
  • amazon-linux-2023-upgrade-kernel-livepatch-6-1-82-99-168
  • amazon-linux-2023-upgrade-kernel-modules-extra
  • amazon-linux-2023-upgrade-kernel-modules-extra-common
  • amazon-linux-2023-upgrade-kernel-tools
  • amazon-linux-2023-upgrade-kernel-tools-debuginfo
  • amazon-linux-2023-upgrade-kernel-tools-devel
  • amazon-linux-2023-upgrade-perf
  • amazon-linux-2023-upgrade-perf-debuginfo
  • amazon-linux-2023-upgrade-python3-perf
  • amazon-linux-2023-upgrade-python3-perf-debuginfo

References

  • https://attackerkb.com/topics/cve-2024-26737
  • CVE - 2024-26737
  • https://alas.aws.amazon.com/AL2023/ALAS-2024-784.html
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