Linux Kernel up to 7.2.5 POSIX CPU Timers spinlock_rt.c run_posix_cpu_timers siglock locking

Summaryinfo

A vulnerability, which was classified as very critical, has been found in Linux Kernel up to 7.2.5. The affected element is the function run_posix_cpu_timers of the file spinlock_rt.c of the component POSIX CPU Timers. The manipulation of the argument siglock leads to locking. This vulnerability is documented as CVE-2026-90305. The attack needs to be performed locally. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.5 and classified as very critical. This issue affects the function run_posix_cpu_timers of the file spinlock_rt.c of the component POSIX CPU Timers. The manipulation of the argument siglock with an unknown input leads to a locking vulnerability. Using CWE to declare the problem leads to CWE-667. The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ARM: 9483/1: select HAVE_POSIX_CPU_TIMERS_TASK_WORK Commit c6e61c06d606 ("ARM: 9463/1: Allow to enable RT") enabled PREEMPT_RT on ARM but did not select HAVE_POSIX_CPU_TIMERS_TASK_WORK. This leaves CONFIG_POSIX_CPU_TIMERS_TASK_WORK disabled, so CPU timers expire in hard IRQ context. On PREEMPT_RT this makes run_posix_cpu_timers() take the sleeping sighand->siglock: BUG: sleeping function called from invalid context at spinlock_rt.c:48 rt_spin_lock from lock_task_sighand lock_task_sighand from run_posix_cpu_timers run_posix_cpu_timers from update_process_times ARM handles TIF_NOTIFY_RESUME on all return-to-user paths, including v7-M. ARM32 KVM host support was removed by commit 541ad0150ca4 ("arm: Remove 32bit KVM host support"), so the select need not be conditional on KVM. Select it to defer POSIX CPU timer expiry to task context. Reproduced with setrlimit(RLIMIT_CPU, ...) and a busy loop. The same path is used by setitimer(ITIMER_PROF or ITIMER_VIRTUAL) and POSIX CPU timers created with timer_create().

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-90305 since 09/11/2026. The exploitation is known to be easy. An attack has to be approached locally. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/17/2026).

Upgrading to version 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch 8de56782d6e5ba7a9f8c820342dccde65502f93f/8a58a41100ea377e978d99600ec24a9bd0273662 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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