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authorSuren Baghdasaryan <surenb@google.com>2023-06-30 03:56:12 +0300
committerPeter Zijlstra <peterz@infradead.org>2023-07-10 10:52:30 +0300
commitaff037078ecaecf34a7c2afab1341815f90fba5e (patch)
tree7a6bafd925d74b2b5cf387dc23601a4265b997d3 /include/linux
parentae2ad293d6be143ad223f5f947cca07bcbe42595 (diff)
downloadlinux-aff037078ecaecf34a7c2afab1341815f90fba5e.tar.xz
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.h5
-rw-r--r--include/linux/psi_types.h3
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;