diff options
| author | Suren Baghdasaryan <surenb@google.com> | 2023-06-29 17:56:12 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-07-10 09:52:30 +0200 |
| commit | aff037078ecaecf34a7c2afab1341815f90fba5e (patch) | |
| tree | 7a6bafd925d74b2b5cf387dc23601a4265b997d3 /include/linux | |
| parent | ae2ad293d6be143ad223f5f947cca07bcbe42595 (diff) | |
sched/psi: use kernfs polling functions for PSI trigger polling
Destroying psi trigger in cgroup_file_release causes UAF issues when
a cgroup is removed from under a polling process. This is happening
because cgroup removal causes a call to cgroup_file_release while the
actual file is still alive. Destroying the trigger at this point would
also destroy its waitqueue head and if there is still a polling process
on that file accessing the waitqueue, it will step on the freed pointer:
do_select
vfs_poll
do_rmdir
cgroup_rmdir
kernfs_drain_open_files
cgroup_file_release
cgroup_pressure_release
psi_trigger_destroy
wake_up_pollfree(&t->event_wait)
// vfs_poll is unblocked
synchronize_rcu
kfree(t)
poll_freewait -> UAF access to the trigger's waitqueue head
Patch [1] fixed this issue for epoll() case using wake_up_pollfree(),
however the same issue exists for synchronous poll() case.
The root cause of this issue is that the lifecycles of the psi trigger's
waitqueue and of the file associated with the trigger are different. Fix
this by using kernfs_generic_poll function when polling on cgroup-specific
psi triggers. It internally uses kernfs_open_node->poll waitqueue head
with its lifecycle tied to the file's lifecycle. This also renders the
fix in [1] obsolete, so revert it.
[1] commit c2dbe32d5db5 ("sched/psi: Fix use-after-free in ep_remove_wait_queue()")
Fixes: 0e94682b73bf ("psi: introduce psi monitor")
Closes: https://lore.kernel.org/all/20230613062306.101831-1-lujialin4@huawei.com/
Reported-by: Lu Jialin <lujialin4@huawei.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230630005612.1014540-1-surenb@google.com
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/psi.h | 5 | ||||
| -rw-r--r-- | include/linux/psi_types.h | 3 |
2 files changed, 6 insertions, 2 deletions
diff --git a/include/linux/psi.h b/include/linux/psi.h index ab26200c2803..e0745873e3f2 100644 --- a/include/linux/psi.h +++ b/include/linux/psi.h @@ -23,8 +23,9 @@ void psi_memstall_enter(unsigned long *flags); void psi_memstall_leave(unsigned long *flags); int psi_show(struct seq_file *s, struct psi_group *group, enum psi_res res); -struct psi_trigger *psi_trigger_create(struct psi_group *group, - char *buf, enum psi_res res, struct file *file); +struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf, + enum psi_res res, struct file *file, + struct kernfs_open_file *of); void psi_trigger_destroy(struct psi_trigger *t); __poll_t psi_trigger_poll(void **trigger_ptr, struct file *file, diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h index 040c089581c6..f1fd3a8044e0 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h @@ -137,6 +137,9 @@ struct psi_trigger { /* Wait queue for polling */ wait_queue_head_t event_wait; + /* Kernfs file for cgroup triggers */ + struct kernfs_open_file *of; + /* Pending event flag */ int event; |