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 7ED3D3D8130 for ; Wed, 20 May 2026 14:41:41 +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=1779288102; cv=none; b=GaL8Buc8+82UgtXE+SjepL06SFcgZTruCyCgG9MYwOtNUsSPPIPWo2j2Pifp7cigeQG+wKRSw3DfJhcljOuRuKfrdWbGVE5POxjK+2K6FqYHGVY6FBpD/r7YrQfvg1cwamgsMHDhcJwJqrEni5cRBA+NZ5g6a6Dq2jZCO51RkYI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779288102; c=relaxed/simple; bh=2VLXjvz75Ar/4Jj3DavhPQYWXQjYmeDKKj25Uv6YWAc=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=ctj2970guQi02kdX21AmqImICQ82Nn91S0/pbelOU6dxaOdhPKHqfFnS71FBrNmH7iz5N0xAMc5QzApBq78OqINiv+rYOt3aR4nydsCMhFE5d3V3n0hCDZXHo1WLfjWdVi+L7PxjLSUoDQ4U13asfctyjDcpjqumU82cwgQ4LKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vpJAORba; 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="vpJAORba" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E21201F000E9; Wed, 20 May 2026 14:41:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779288101; bh=Koa59LwEfkGE5hkdc2aAutXWuMvfdctjyPrYzzjEdgc=; h=Subject:To:Cc:From:Date; b=vpJAORba8JTfcxDBNRjELkbTRDKAVnWB7H78xrg5qoD/4Q3aC7hXTgNUy9wIWSh1h LqPfR39jEHiGpfNLwyPh6tmcYRyFAZTZsbxcuf6GdhWbM/Gl7ydKgLa3Z3JTiKfJo1 zS8lhd/yj8XkQJ9gcfoLrQa7rep1n1M/dNoA7b8k= Subject: FAILED: patch "[PATCH] io-wq: check that the predecessor is hashed in" failed to apply to 5.15-stable tree To: nicholas@carlini.com,axboe@kernel.dk Cc: From: Date: Wed, 20 May 2026 16:41:36 +0200 Message-ID: <2026052036-arbitrate-wasp-6200@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x d6a2d7b04b5a093021a7a0e2e69e9d5237dfa8cc # git commit -s git send-email --to '' --in-reply-to '2026052036-arbitrate-wasp-6200@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d6a2d7b04b5a093021a7a0e2e69e9d5237dfa8cc Mon Sep 17 00:00:00 2001 From: Nicholas Carlini Date: Mon, 11 May 2026 18:02:16 +0000 Subject: [PATCH] io-wq: check that the predecessor is hashed in io_wq_remove_pending() io_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled work was the tail of its hash bucket. When doing this, it checks whether the preceding entry in acct->work_list has the same hash value, but never checks that the predecessor is hashed at all. io_get_work_hash() is simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash bits are never set for non-hashed work, so it returns 0. Thus, when a hashed bucket-0 work is cancelled while a non-hashed work is its list predecessor, the check spuriously passes and a pointer to the non-hashed io_kiocb is stored in wq->hash_tail[0]. Because non-hashed work is dequeued via the fast path in io_get_next_work(), which never touches hash_tail[], the stale pointer is never cleared. Therefore, after the non-hashed io_kiocb completes and is freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The io_wq is per-task (tctx->io_wq) and survives ring open/close, so the dangling pointer persists for the lifetime of the task; the next hashed bucket-0 enqueue dereferences it in io_wq_insert_work() and wq_list_add_after() writes through freed memory. Add the missing io_wq_is_hashed() check so a non-hashed predecessor never inherits a hash_tail[] slot. Cc: stable@vger.kernel.org Fixes: 204361a77f40 ("io-wq: fix hang after cancelling pending hashed work") Signed-off-by: Nicholas Carlini Signed-off-by: Jens Axboe diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 7a9f94a0ce6f..8cc7b47d3089 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -1124,7 +1124,8 @@ static inline void io_wq_remove_pending(struct io_wq *wq, if (io_wq_is_hashed(work) && work == wq->hash_tail[hash]) { if (prev) prev_work = container_of(prev, struct io_wq_work, list); - if (prev_work && io_get_work_hash(prev_work) == hash) + if (prev_work && io_wq_is_hashed(prev_work) && + io_get_work_hash(prev_work) == hash) wq->hash_tail[hash] = prev_work; else wq->hash_tail[hash] = NULL;