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io-wq: kill hashed waitqueue before manager exits 

If we race with shutting down the io-wq context and someone queueing
a hashed entry, then we can exit the manager with it armed. If it then
triggers after the manager has exited, we can have a use-after-free where
io_wqe_hash_wake() attempts to wake a now gone manager process.

Move the killing of the hashed write queue into the manager itself, so
that we know we've killed it before the task exits.

Fixes: e941894eae ("io-wq: make buffered file write hashed work map per-ctx")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-03-05 08:14:08 -07:00
parent b5b0ecb736
commit 09ca6c40c2
1 changed files with 5 additions and 4 deletions
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9
fs/io-wq.c
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@ -726,6 +726,11 @@ static int io_wq_manager(void *data)
if (atomic_read(&wq->worker_refs))
wait_for_completion(&wq->worker_done);
spin_lock_irq(&wq->hash->wait.lock);
for_each_node(node)
list_del_init(&wq->wqes[node]->wait.entry);
spin_unlock_irq(&wq->hash->wait.lock);
io_wq_cancel_pending(wq);
complete(&wq->exited);
do_exit(0);
@ -1051,15 +1056,11 @@ static void io_wq_destroy(struct io_wq *wq)
set_bit(IO_WQ_BIT_EXIT, &wq->state);
io_wq_destroy_manager(wq);
spin_lock_irq(&wq->hash->wait.lock);
for_each_node(node) {
struct io_wqe *wqe = wq->wqes[node];
list_del_init(&wqe->wait.entry);
WARN_ON_ONCE(!wq_list_empty(&wqe->work_list));
kfree(wqe);
}
spin_unlock_irq(&wq->hash->wait.lock);
io_wq_put_hash(wq->hash);
kfree(wq->wqes);
kfree(wq);