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CVE-2024-46786

Description

In the Linux kernel, the following vulnerability has been resolved:fscache: delete fscache_cookie_lru_timer when fscache exits to avoid UAFThe fscache_cookie_lru_timer is initialized when the fscache moduleis inserted, but is not deleted when the fscache module is removed.If timer_reduce() is called before removing the fscache module,the fscache_cookie_lru_timer will be added to the timer list ofthe current cpu. Afterwards, a use-after-free will be triggeredin the softIRQ after removing the fscache module, as follows:==================================================================BUG: unable to handle page fault for address: fffffbfff803c9e9 PF: supervisor read access in kernel mode PF: error_code(0x0000) - not-present pagePGD 21ffea067 P4D 21ffea067 PUD 21ffe6067 PMD 110a7c067 PTE 0Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTICPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G W 6.11.0-rc3 #855Tainted: [W]=WARNRIP: 0010:__run_timer_base.part.0+0x254/0x8a0Call Trace: tmigr_handle_remote_up+0x627/0x810 __walk_groups.isra.0+0x47/0x140 tmigr_handle_remote+0x1fa/0x2f0 handle_softirqs+0x180/0x590 irq_exit_rcu+0x84/0xb0 sysvec_apic_timer_interrupt+0x6e/0x90 asm_sysvec_apic_timer_interrupt+0x1a/0x20RIP: 0010:default_idle+0xf/0x20 default_idle_call+0x38/0x60 do_idle+0x2b5/0x300 cpu_startup_entry+0x54/0x60 start_secondary+0x20d/0x280 common_startup_64+0x13e/0x148 Modules linked in: [last unloaded: netfs]==================================================================Therefore delete fscache_cookie_lru_timer when removing the fscahe module.

POC

Reference

No PoCs from references.

Github

- https://github.com/bygregonline/devsec-fastapi-report