| Message ID | 20230214181335.3946674-1-kamatam@amazon.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] sched/psi: fix use-after-free in ep_remove_wait_queue() | expand |
On Tue, Feb 14, 2023 at 10:13 AM Munehisa Kamata <kamatam@amazon.com> 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: > <TASK> > 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 > </TASK> > > 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 <kamatam@amazon.com> > Signed-off-by: Mengchi Cheng <mengcc@amazon.com> Acked-by: Suren Baghdasaryan <surenb@google.com> > --- > 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 >
On Tue, Feb 14, 2023 at 10:28 AM Suren Baghdasaryan <surenb@google.com> wrote: > > On Tue, Feb 14, 2023 at 10:13 AM Munehisa Kamata <kamatam@amazon.com> 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: > > <TASK> > > 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 > > </TASK> > > > > 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 <kamatam@amazon.com> > > Signed-off-by: Mengchi Cheng <mengcc@amazon.com> > Acked-by: Suren Baghdasaryan <surenb@google.com> CC'ing PeterZ directly for inclusion into his tree. > > > --- > > 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 > >
On Tue, Feb 14, 2023 at 10:13:35AM -0800, Munehisa Kamata wrote: > 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. If that comment is outdated now, then please update the comment too. We can do better than "not fully contradicting". - Eric
On Tue, Feb 14, 2023 at 10:55 AM Eric Biggers <ebiggers@kernel.org> wrote: > > On Tue, Feb 14, 2023 at 10:13:35AM -0800, Munehisa Kamata wrote: > > 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. > > If that comment is outdated now, then please update the comment too. We can do > better than "not fully contradicting". Agree. I don't see it contradicting that comment. > > - Eric
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);
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: <TASK> 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 </TASK> 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 <kamatam@amazon.com> Signed-off-by: Mengchi Cheng <mengcc@amazon.com> --- kernel/sched/psi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)