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 12E423F4DCC; Wed, 20 May 2026 17:15:30 +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=1779297332; cv=none; b=MFbCsFQciujYXYm8UwntMhVXOn4uFWoKa+ftMy9zG7ByL4ksIrhveKedZM+KQPUfDaJfBweLeO3PzcPWqbRpbIqE668GIx+V9B95jZYbT8WV03KzbhP1AGYNP47sGKy8Q3N0046WqKkaHwQUK3qzH1zn0mOvm/UOpoKrKPwN99I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779297332; c=relaxed/simple; bh=gk95xzrhW1HS+n3nui6aOvQRvfmCvenr8W60NHPsOvE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FJRtPd7CyjtX5jiyTwqaxjwdbhPUFr7zQsAiK3eyOMO92ycsjdfj3PVwWnW0zLYx08nKdg9WydTX0Or6xw8sy4XDYY4guZQQnE01nqd/mZ/dW+JkVnrnfDIkvCvrfN/p4X9QmA8GHgcnhPX0SL5NtmBpPzsq9Oqz0ITz8Eg+lxY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xu4ikFQA; 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="xu4ikFQA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 396811F000E9; Wed, 20 May 2026 17:15:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779297330; bh=AL8J+QawhwppXMlPloe8fJNk4EBfUr6aai3Th4STYDE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xu4ikFQAeRBwrUFnYG/v+SXYemeOC8boB+qTqgXcJ4boPZHEm/1bi9auaOBBsDMEQ FSr1uAoNlJcio+3zrNUeMzZLl3m69HhqcGJdILR/gRu50YQSn2J89ziILbEm+4/HQz 0fsPXewMJCkaXekTQKQx/zRuZTyF+CVYP92sobS4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nicholas Carlini , Jens Axboe Subject: [PATCH 7.0 1097/1146] io-wq: check that the predecessor is hashed in io_wq_remove_pending() Date: Wed, 20 May 2026 18:22:27 +0200 Message-ID: <20260520162213.069088714@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162148.390695140@linuxfoundation.org> References: <20260520162148.390695140@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nicholas Carlini commit d6a2d7b04b5a093021a7a0e2e69e9d5237dfa8cc upstream. 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 Signed-off-by: Greg Kroah-Hartman --- io_uring/io-wq.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -1124,7 +1124,8 @@ static inline void io_wq_remove_pending( 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;