In the Linux kernel, the following vulnerability has been resolved: f2fs: fix race in concurrent f2fs_stop_gc_thread In my test case, concurrent calls to f2fs shutdown report the following stack trace: Oops: general protection fault, probably for non-canonical address 0xc6cfff63bb5513fc: 0000 [#1] PREEMPT SMP PTI CPU: 0 UID: 0 PID: 678 Comm: f2fs_rep_shutdo Not tainted 6.12.0-rc5-next-20241029-g6fb2fa9805c5-dirty #85 Call Trace: <TASK> ? show_regs+0x8b/0xa0 ? __die_body+0x26/0xa0 ? die_addr+0x54/0x90 ? exc_general_protection+0x24b/0x5c0 ? asm_exc_general_protection+0x26/0x30 ? kthread_stop+0x46/0x390 f2fs_stop_gc_thread+0x6c/0x110 f2fs_do_shutdown+0x309/0x3a0 f2fs_ioc_shutdown+0x150/0x1c0 __f2fs_ioctl+0xffd/0x2ac0 f2fs_ioctl+0x76/0xe0 vfs_ioctl+0x23/0x60 __x64_sys_ioctl+0xce/0xf0 x64_sys_call+0x2b1b/0x4540 do_syscall_64+0xa7/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e The root cause is a race condition in f2fs_stop_gc_thread() called from different f2fs shutdown paths: [CPU0] [CPU1] ---------------------- ----------------------- f2fs_stop_gc_thread f2fs_stop_gc_thread gc_th = sbi->gc_thread gc_th = sbi->gc_thread kfree(gc_th) sbi->gc_thread = NULL < gc_th != NULL > kthread_stop(gc_th->f2fs_gc_task) //UAF The commit c7f114d864ac ("f2fs: fix to avoid use-after-free in f2fs_stop_gc_thread()") attempted to fix this issue by using a read semaphore to prevent races between shutdown and remount threads, but it fails to prevent all race conditions. Fix it by converting to write lock of s_umount in f2fs_do_shutdown().
| Métrique | Valeur | Interprétation |
|---|---|---|
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AV (Vecteur d'Attaque)
Attack Vector
|
Local (L)
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Exploit nécessite un accès local au système |
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AC (Complexité d'Attaque)
Attack Complexity
|
Low (L)
|
Peu de conditions requises pour exploiter |
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PR (Privilèges Requis)
Privileges Required
|
Low (L)
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Authentifié avec compte utilisateur basique |
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UI (Interaction Utilisateur)
User Interaction
|
None (N)
|
Aucune interaction utilisateur nécessaire |
|
S (Périmètre)
Scope
|
Unchanged (U)
|
Impact reste dans le périmètre du composant compromis |
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C (Impact Confidentialité)
Confidentiality Impact
|
High (H)
|
Divulgation totale d'informations |
|
I (Impact Intégrité)
Integrity Impact
|
High (H)
|
Modification totale des données possible |
|
A (Impact Disponibilité)
Availability Impact
|
High (H)
|
Interruption totale du service possible |
f2fs: fix race in concurrent f2fs_stop_gc_thread