From: Baokun Li libaokun1@huawei.com

commit 72a6e22c604c95ddb3b10b5d3bb85b6ff4dbc34f upstream.

The fscache_cookie_lru_timer is initialized when the fscache module is 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 of the current cpu. Afterwards, a use-after-free will be triggered in 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 page PGD 21ffea067 P4D 21ffea067 PUD 21ffe6067 PMD 110a7c067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G W 6.11.0-rc3 #855 Tainted: [W]=WARN RIP: 0010:__run_timer_base.part.0+0x254/0x8a0 Call Trace: <IRQ> 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 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 RIP: 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 </TASK> Modules linked in: [last unloaded: netfs] ==================================================================

Therefore delete fscache_cookie_lru_timer when removing the fscahe module.

Fixes: 12bb21a29c19 ("fscache: Implement cookie user counting and resource pinning") Cc: stable@kernel.org Signed-off-by: Baokun Li libaokun1@huawei.com Link: https://lore.kernel.org/r/20240826112056.2458299-1-libaokun@huaweicloud.com Acked-by: David Howells dhowells@redhat.com Signed-off-by: Christian Brauner brauner@kernel.org [kovalev: use the `del_timer_sync()` call instead of `timer_shutdown_sync()`] Signed-off-by: Vasiliy Kovalev kovalev@altlinux.org --- Backport to fix CVE-2024-46786 Link: https://www.cve.org/CVERecord/?id=CVE-2024-46786 --- fs/fscache/main.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/fs/fscache/main.c b/fs/fscache/main.c index dad85fd84f6f9f..dc37c9df3bef7d 100644 --- a/fs/fscache/main.c +++ b/fs/fscache/main.c @@ -114,6 +114,7 @@ static void __exit fscache_exit(void)

kmem_cache_destroy(fscache_cookie_jar); fscache_proc_cleanup(); + del_timer_sync(&fscache_cookie_lru_timer); destroy_workqueue(fscache_wq); pr_notice("Unloaded\n"); }