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authorSuren Baghdasaryan <surenb@google.com>2022-01-11 15:23:09 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-02-05 12:37:55 +0100
commitd4e4e61d4a5b87bfc9953c306a11d35d869417fd (patch)
tree55da4678067b5c22a812bec3d3f279574b73517b /include
parent080dbe7e9b86a0392d8dffc00d9971792afc121f (diff)
psi: Fix uaf issue when psi trigger is destroyed while being polled
commit a06247c6804f1a7c86a2e5398a4c1f1db1471848 upstream. With write operation on psi files replacing old trigger with a new one, the lifetime of its waitqueue is totally arbitrary. Overwriting an existing trigger causes its waitqueue to be freed and pending poll() will stumble on trigger->event_wait which was destroyed. Fix this by disallowing to redefine an existing psi trigger. If a write operation is used on a file descriptor with an already existing psi trigger, the operation will fail with EBUSY error. Also bypass a check for psi_disabled in the psi_trigger_destroy as the flag can be flipped after the trigger is created, leading to a memory leak. Fixes: 0e94682b73bf ("psi: introduce psi monitor") Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Analyzed-by: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com [surenb: backported to 5.10 kernel] CC: stable@vger.kernel.org # 5.10 Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/psi.h2
-rw-r--r--include/linux/psi_types.h3
2 files changed, 1 insertions, 4 deletions
diff --git a/include/linux/psi.h b/include/linux/psi.h
index 7361023f3fdd..db4ecfaab879 100644
--- a/include/linux/psi.h
+++ b/include/linux/psi.h
@@ -33,7 +33,7 @@ void cgroup_move_task(struct task_struct *p, struct css_set *to);
struct psi_trigger *psi_trigger_create(struct psi_group *group,
char *buf, size_t nbytes, enum psi_res res);
-void psi_trigger_replace(void **trigger_ptr, struct psi_trigger *t);
+void psi_trigger_destroy(struct psi_trigger *t);
__poll_t psi_trigger_poll(void **trigger_ptr, struct file *file,
poll_table *wait);
diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index b95f3211566a..17d74f62c181 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -128,9 +128,6 @@ struct psi_trigger {
* events to one per window
*/
u64 last_event_time;
-
- /* Refcounting to prevent premature destruction */
- struct kref refcount;
};
struct psi_group {