6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joanne Koong [ Upstream commit 42df916e5a5f8fb4b60c8cefb54318d1ec02c580 ] fuse_uring_create_queue() initializes a fuse_ring_queue and then publishes the pointer into ring->queues[qid] with WRITE_ONCE() under the fch->lock. There are several readers that may concurrently be fetching that pointer locklessly and then deferencing it. WRITE_ONCE() doesn't ensure ordering of the queue's field initialization before the ring->queues[qid] pointer assignment. The queue must be published with smp_store_release() so the field initialization is guaranteed to happen before. Readers in paths where the read may happen concurrently with the store need to use READ_ONCE() because any race involving a plain access is undefined. Fixes: 24fe962c86f5 ("fuse: {io-uring} Handle SQEs - register commands") Cc: stable@vger.kernel.org Reviewed-by: Bernd Schubert Signed-off-by: Joanne Koong Signed-off-by: Miklos Szeredi [ renamed `fch->lock` to `fc->lock` since this tree lacks `struct fuse_chan` ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/fuse/dev_uring.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) --- a/fs/fuse/dev_uring.c +++ b/fs/fuse/dev_uring.c @@ -194,7 +194,7 @@ void fuse_uring_destruct(struct fuse_con return; for (qid = 0; qid < ring->nr_queues; qid++) { - struct fuse_ring_queue *queue = ring->queues[qid]; + struct fuse_ring_queue *queue = READ_ONCE(ring->queues[qid]); struct fuse_ring_ent *ent, *next; if (!queue) @@ -213,7 +213,7 @@ void fuse_uring_destruct(struct fuse_con kfree(queue->fpq.processing); kfree(queue); - ring->queues[qid] = NULL; + WRITE_ONCE(ring->queues[qid], NULL); } kfree(ring->queues); @@ -307,9 +307,11 @@ static struct fuse_ring_queue *fuse_urin } /* - * write_once and lock as the caller mostly doesn't take the lock at all + * fc->lock serializes concurrent creators for this qid. + * smp_store_release() are for the lockless readers who must see a + * fully initialized queue after &ring->queues[qid] is set */ - WRITE_ONCE(ring->queues[qid], queue); + smp_store_release(&ring->queues[qid], queue); spin_unlock(&fc->lock); return queue; @@ -406,7 +408,7 @@ static void fuse_uring_log_ent_state(str struct fuse_ring_ent *ent; for (qid = 0; qid < ring->nr_queues; qid++) { - struct fuse_ring_queue *queue = ring->queues[qid]; + struct fuse_ring_queue *queue = READ_ONCE(ring->queues[qid]); if (!queue) continue; @@ -911,7 +913,7 @@ static int fuse_uring_commit_fetch(struc if (qid >= ring->nr_queues) return -EINVAL; - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); if (!queue) return err; fpq = &queue->fpq; @@ -980,7 +982,7 @@ static bool is_ring_ready(struct fuse_ri if (current_qid == qid) continue; - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); if (!queue) { ready = false; break; @@ -1134,7 +1136,7 @@ static int fuse_uring_register(struct io return -EINVAL; } - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); if (!queue) { queue = fuse_uring_create_queue(ring, qid); if (!queue) @@ -1286,7 +1288,7 @@ static struct fuse_ring_queue *fuse_urin ring->nr_queues)) qid = 0; - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); WARN_ONCE(!queue, "Missing queue for qid %d\n", qid); return queue;