From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E8B2E2DB7BF for ; Mon, 31 Aug 2026 12:23:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788178986; cv=none; b=KNBgYlSQmMPWsjYRG7uPKqWcbZMEW03qOJF+hvDq+SoZS/ZifoV/gcIaFCChK0rm6e9VKrfuvCtGnuzPV6FgWP+JGmLDzD97Ruk1FEuzBy8P6tISGFC0/GgU5E69ArTgKCBp6yaYjF3H/ZhMmEkPO/Lw15Zb5b4a9VqthIexkuc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788178986; c=relaxed/simple; bh=O7Z/RQjeCn6BDPplwhcqO31oS6VxgpZQKPKP8XuBcdg=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=NwolpVyZjGaZhpkeewMp0UjTomSHVkw/wz/vHuKAiqQtoNquah58VmmDKGKPGZnwpjPlZmCxhXu3dyG9xxTRnok9bSoDX4H4rF3nqyuEGKRl1rqRKz0qyi5PlgSSvQLwCCye6SRjpztMquDA1DbUQgIFOZ2DxD5EdN/KpbHucdQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zRUFGKeu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zRUFGKeu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 503D41F000E9; Mon, 31 Aug 2026 12:23:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788178984; bh=yDsMvQ1xtJBVooy/0Qmys4mSG6wizfpaWeAIbFVfi8s=; h=Subject:To:Cc:From:Date; b=zRUFGKeu5SZnlW+3DLc7rz3BHHtzjCjBEWoG375lvLEAAMT+XZKe9NGXMwxDBqgcN r9yIHhtShXXVCTsQyiAFTCjRUEE2LBFTsmERfMDSx3KwyhHof3Gvfjp8gEHIOO91Be bO1kyCFZqWG+4jHwA5GMwh9lsruz6Lwhp87j6y6U= Subject: FAILED: patch "[PATCH] fuse: publish io-uring queues with release semantics" failed to apply to 6.18-stable tree To: joannelkoong@gmail.com,bernd@bsbernd.com,mszeredi@redhat.com Cc: From: Date: Mon, 31 Aug 2026 14:22:52 +0200 Message-ID: <2026083152-cucumber-unwieldy-2691@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 42df916e5a5f8fb4b60c8cefb54318d1ec02c580 # git commit -s git send-email --to '' --in-reply-to '2026083152-cucumber-unwieldy-2691@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 42df916e5a5f8fb4b60c8cefb54318d1ec02c580 Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Thu, 16 Jul 2026 11:31:44 -0700 Subject: [PATCH] fuse: publish io-uring queues with release semantics 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 diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c index 51f985154aa1..c8488ebc1d1f 100644 --- a/fs/fuse/dev_uring.c +++ b/fs/fuse/dev_uring.c @@ -204,7 +204,7 @@ void fuse_uring_destruct(struct fuse_chan *fch) 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) @@ -223,7 +223,7 @@ void fuse_uring_destruct(struct fuse_chan *fch) kfree(queue->fpq.processing); kfree(queue); - ring->queues[qid] = NULL; + WRITE_ONCE(ring->queues[qid], NULL); } kfree(ring->queues); @@ -321,9 +321,11 @@ static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring, } /* - * write_once and lock as the caller mostly doesn't take the lock at all + * fch->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(&fch->lock); return queue; @@ -434,7 +436,7 @@ static void fuse_uring_log_ent_state(struct fuse_ring *ring) 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; @@ -967,7 +969,7 @@ static int fuse_uring_commit_fetch(struct io_uring_cmd *cmd, int issue_flags, if (qid >= ring->nr_queues) return -EINVAL; - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); if (!queue) return err; fpq = &queue->fpq; @@ -1035,7 +1037,7 @@ static bool is_ring_ready(struct fuse_ring *ring, int current_qid) if (current_qid == qid) continue; - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); if (!queue) { ready = false; break; @@ -1191,7 +1193,7 @@ static int fuse_uring_register(struct io_uring_cmd *cmd, return -EINVAL; } - queue = ring->queues[qid]; + queue = READ_ONCE(ring->queues[qid]); if (!queue) { queue = fuse_uring_create_queue(ring, qid); if (!queue) @@ -1332,7 +1334,7 @@ static struct fuse_ring_queue *fuse_uring_task_to_queue(struct fuse_ring *ring) 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;