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Tue, 14 Feb 2023 18:13:52 +0000 From: Munehisa Kamata To: CC: , , , , , , , Subject: [PATCH v3] sched/psi: fix use-after-free in ep_remove_wait_queue() Date: Tue, 14 Feb 2023 10:13:35 -0800 Message-ID: <20230214181335.3946674-1-kamatam@amazon.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 X-Originating-IP: [10.43.162.56] X-ClientProxiedBy: EX13D40UWA004.ant.amazon.com (10.43.160.36) To EX19D010UWA004.ant.amazon.com (10.13.138.204) X-Rspamd-Queue-Id: 21D2C40008 X-Stat-Signature: ry37i6i1z9cq5r1uphbnq9heerktw5ub X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1676398437-768156 X-HE-Meta: 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 B6+ScqW6 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: If a non-root cgroup gets removed when there is a thread that registered trigger and is polling on a pressure file within the cgroup, the polling waitqueue gets freed in the following path. do_rmdir cgroup_rmdir kernfs_drain_open_files cgroup_file_release cgroup_pressure_release psi_trigger_destroy However, the polling thread still has a reference to the pressure file and will access the freed waitqueue when the file is closed or upon exit. fput ep_eventpoll_release ep_free ep_remove_wait_queue remove_wait_queue This results in use-after-free as pasted below. The fundamental problem here is that cgroup_file_release() (and consequently waitqueue's lifetime) is not tied to the file's real lifetime. Using wake_up_pollfree() here might be less than ideal, but it also is not fully contradicting the comment at commit 42288cb44c4b ("wait: add wake_up_pollfree()") since the waitqueue's lifetime is not tied to file's one and can be considered as another special case. While this would be fixable by somehow making cgroup_file_release() be tied to the fput(), it would require sizable refactoring at cgroups or higher layer which might be more justifiable if we identify more cases like this. BUG: KASAN: use-after-free in _raw_spin_lock_irqsave+0x60/0xc0 Write of size 4 at addr ffff88810e625328 by task a.out/4404 CPU: 19 PID: 4404 Comm: a.out Not tainted 6.2.0-rc6 #38 Hardware name: Amazon EC2 c5a.8xlarge/, BIOS 1.0 10/16/2017 Call Trace: dump_stack_lvl+0x73/0xa0 print_report+0x16c/0x4e0 ? _printk+0x59/0x80 ? __virt_addr_valid+0xb8/0x130 ? _raw_spin_lock_irqsave+0x60/0xc0 kasan_report+0xc3/0xf0 ? _raw_spin_lock_irqsave+0x60/0xc0 kasan_check_range+0x2d2/0x310 _raw_spin_lock_irqsave+0x60/0xc0 remove_wait_queue+0x1a/0xa0 ep_free+0x12c/0x170 ep_eventpoll_release+0x26/0x30 __fput+0x202/0x400 task_work_run+0x11d/0x170 do_exit+0x495/0x1130 ? update_cfs_rq_load_avg+0x2c2/0x2e0 do_group_exit+0x100/0x100 get_signal+0xd67/0xde0 ? finish_task_switch+0x15f/0x3a0 arch_do_signal_or_restart+0x2a/0x2b0 exit_to_user_mode_prepare+0x94/0x100 syscall_exit_to_user_mode+0x20/0x40 do_syscall_64+0x52/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f8e392bfb91 Code: Unable to access opcode bytes at 0x7f8e392bfb67. RSP: 002b:00007fff261e08d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000022 RAX: fffffffffffffdfe RBX: 0000000000000000 RCX: 00007f8e392bfb91 RDX: 0000000000000001 RSI: 00007fff261e08e8 RDI: 0000000000000004 RBP: 00007fff261e0920 R08: 0000000000400780 R09: 00007f8e3960f240 R10: 00000000000003df R11: 0000000000000246 R12: 00000000004005a0 R13: 00007fff261e0a00 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 4404: kasan_set_track+0x3d/0x60 __kasan_kmalloc+0x85/0x90 psi_trigger_create+0x113/0x3e0 pressure_write+0x146/0x2e0 cgroup_file_write+0x11c/0x250 kernfs_fop_write_iter+0x186/0x220 vfs_write+0x3d8/0x5c0 ksys_write+0x90/0x110 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 4407: kasan_set_track+0x3d/0x60 kasan_save_free_info+0x27/0x40 ____kasan_slab_free+0x11d/0x170 slab_free_freelist_hook+0x87/0x150 __kmem_cache_free+0xcb/0x180 psi_trigger_destroy+0x2e8/0x310 cgroup_file_release+0x4f/0xb0 kernfs_drain_open_files+0x165/0x1f0 kernfs_drain+0x162/0x1a0 __kernfs_remove+0x1fb/0x310 kernfs_remove_by_name_ns+0x95/0xe0 cgroup_addrm_files+0x67f/0x700 cgroup_destroy_locked+0x283/0x3c0 cgroup_rmdir+0x29/0x100 kernfs_iop_rmdir+0xd1/0x140 vfs_rmdir+0xfe/0x240 do_rmdir+0x13d/0x280 __x64_sys_rmdir+0x2c/0x30 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd v3: updated commit message and the comment in the code v2: updated commit message Link: https://lore.kernel.org/lkml/20230106224859.4123476-1-kamatam@amazon.com/ Fixes: 0e94682b73bf ("psi: introduce psi monitor") Cc: stable@vger.kernel.org Signed-off-by: Munehisa Kamata Signed-off-by: Mengchi Cheng Acked-by: Suren Baghdasaryan Acked-by: Suren Baghdasaryan --- kernel/sched/psi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 8ac8b81bfee6..02e011cabe91 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1343,10 +1343,11 @@ void psi_trigger_destroy(struct psi_trigger *t) group = t->group; /* - * Wakeup waiters to stop polling. Can happen if cgroup is deleted - * from under a polling process. + * Wakeup waiters to stop polling and clear the queue to prevent it from + * being accessed later. Can happen if cgroup is deleted from under a + * polling process. */ - wake_up_interruptible(&t->event_wait); + wake_up_pollfree(&t->event_wait); mutex_lock(&group->trigger_lock);