On Mon, Jan 31, 2022 at 07:06:16PM -0800, Suren Baghdasaryan wrote:
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
Documentation/accounting/psi.rst | 3 +- include/linux/psi.h | 2 +- include/linux/psi_types.h | 3 -- kernel/cgroup/cgroup.c | 11 ++++-- kernel/sched/psi.c | 66 ++++++++++++++------------------ 5 files changed, 40 insertions(+), 45 deletions(-)
Both backports now queued up, thanks.
greg k-h