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charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: b85nwygxbnp3nzemmpr3nnpm5yyjzwyk X-Rspamd-Queue-Id: E12D0140017 X-HE-Tag: 1676399305-66911 X-HE-Meta: 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 CBn6BQ/u V/41V2Vp55B2WjNb5mvUVTr28DDlMDfPdysQNlS76QhVQ9hBr76+LSTRUMS/eK3/E+/2abvN2dUiem9etN4gdTL4rXMZuVEKNlopvVycOs/GB9eqm3EKyRANYTzZJuXDoFZvgIJ04JSmQQ4TYV+YXhAoJXs/N/Es8WESBvMmj/gsoVwRxqZdIujMi46obatUFv9AlxcFB4ElA/7WhsN9QSuzDdYdh0EUgNsV/cLBaHXdv3K2ylGm6jdmm6FnvVi9V/t+moUa2pm9cvdFfEO15jd+eRnWyv+6I6gy7IaPFaO+59dW1lNyTzzdv4+FnNlkeg/I6T7ohEKqCxH/5AYH/E2xNcDh+RHXc6kMXJfR59Zux5UxxpTaZ/wFKqGLi7QQ71foohhfAPqNSXFc= 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: On Tue, Feb 14, 2023 at 10:13 AM Munehisa Kamata wrote: > > 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 > --- > 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); > > -- > 2.38.1 >