Linux Kernel up to 7.2.5 ocfs2 o2hb_arm_timeout use after free

Summaryinfo

A vulnerability, which was classified as very critical, was found in Linux Kernel up to 7.2.5. This issue affects the function o2hb_arm_timeout of the component ocfs2. Executing a manipulation can lead to use after free. This vulnerability appears as CVE-2026-90301. The attack requires local access. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.5. This vulnerability affects the function o2hb_arm_timeout of the component ocfs2. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ocfs2: o2hb: quiesce negotiate handlers and timeout work Heartbeat regions publish struct o2hb_region as the private data for the NEGO_TIMEOUT and NEGO_APPROVE o2net handlers as soon as make_item() creates the configfs region. The approve handler can call o2hb_arm_timeout(), so a peer can touch the region timeout work before dev_store() has finished building the heartbeat runtime, or after teardown has started to shut that runtime back down. The final configfs put also has to keep reg alive until the last in-flight o2net callback drops its handler reference. o2net_unregister_handler_list() blocks future handler lookups, but it does not wait for sc_rx_work that already passed o2net_handler_get(). That drain needs to cover local listener teardown as well, where the o2net ordered workqueue may already be inside destroy_workqueue(). Fix the lifetime rule in both directions. Initialize the region delayed works before publishing reg through the o2net handler table, keep new or stopping regions non-armable with hr_stopping, and quiesce both delayed works on failed-start and teardown paths even when no heartbeat thread is left to call o2hb_disarm_timeout(). Then unregister handlers before tearing down handler-visible region state and make the drain wait for the active or destroying o2net ordered workqueue before release frees reg. The buggy scenario involves two paths, with each column showing the order within that path: region lifecycle: late negotiate callback: 1. make_item() registers the 1. o2net_process_message() gets a region handlers before heartbeat handler for reg. dev_store() has built a 2. The callback runs after the lookup runnable heartbeat context. lock is dropped and dereferences reg. 2. A failed start or rmdir 3. An approve or timeout path tries to stops the heartbeat thread, queue reg's delayed work, or release quiesces existing work, and races the callback body after handler drops the final configfs ref. unregister. 3. region_release() must drain 4. The callback or delayed work can handler-visible o2net rx work outlive reg unless lifecycle code before freeing reg. keeps the region non-armable and drains the active-or-destroying o2net workqueue. Validation reproduced this kernel report: KASAN slab-use-after-free in __run_timers+0x22c/0x5b0 Write of size 8 Call trace: dump_stack_lvl+0x66/0xa0 print_report+0xce/0x630 __run_timers+0x22c/0x5b0 kasan_report+0xe0/0x110 _raw_spin_unlock_irqrestore+0x27/0x60 try_to_wake_up+0x191/0xf70 timer_expire_remote+0xae/0xf0 run_timer_softirq+0x19b/0x1a0 handle_softirqs+0x156/0x660 __irq_exit_rcu+0xc4/0x160 irq_exit_rcu+0xe/0x20 sysvec_apic_timer_interrupt+0x6c/0x80 asm_sysvec_apic_timer_interrupt+0x1a/0x20 Allocated by task stack: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0xaa/0xb0 o2hb_heartbeat_group_make_item+0x3c/0x600

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-90301 since 09/11/2026. The exploitation appears to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/17/2026).

Upgrading to version 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch b5a2907bdeced0949bcddc84b95ba7d4cb93841b/011291b70ba4832e136b7b581825b2bc0f525bf6 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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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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