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 5CBE434389F; Sat, 30 May 2026 17:30:29 +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=1780162230; cv=none; b=jxN8EnICFVh6Belo0Motwxukw0hUpZ9TgEEzwu7FG0QA9UiQvQ8oqbSEIntuyEPBRq11uSe+/6YAMonAkyxstCEf8r918M4NVZgZMRzJZRh29QocNDIXy773z9THVCPbDrMLBrSV12TA2zMbMUsyW8ItVeedK1E5kSrjzdkfRRM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780162230; c=relaxed/simple; bh=azm1CQf30HWxmEZntQe/z7S1HtA2aEo+ceB42OsOWRA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ef8x6wFCT9PE23A2gq+iWHYRhKNe4gArHMZFeqB6dDGDN22oFluJFsiwr1OAFUWbLDIpeubI1zHFDtx4iOsg2F0O7F0vHtzz7CXPEgbnr1FM1S/YRpHfKP3CXg8qHEdAJXN6lx62KPuHsd9EDBRKROwxGex3wBUJ9DcWMNAcqEw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=W6OcspnS; 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="W6OcspnS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 648C71F00898; Sat, 30 May 2026 17:30:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780162229; bh=s09xkT7xhoNk3o8M8rkj4S7wHfS3BihnPZ2Ce3uyiuI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=W6OcspnSXNxe8CofkEN1/jdC2RZi3dbYcB2iN5I4HpVfYFcbhN/LLGgM/m+HVAoEF YjRksO5E5fwIpGG9et3GJKtqQqS/h9J1i6orNLT48cvkyMMGLpgwcleOkX59vpqyzo 2WKrERpJk7mqo/HNviweUa/OSRcBL3V7hyJ+t0hU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nicholas Carlini Subject: [PATCH 6.1 830/969] io-wq: check that the predecessor is hashed in io_wq_remove_pending() Date: Sat, 30 May 2026 18:05:54 +0200 Message-ID: <20260530160323.565337954@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530160300.485627683@linuxfoundation.org> References: <20260530160300.485627683@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nicholas Carlini 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 # 5.7+ Fixes: 204361a77f40 ("io-wq: fix hang after cancelling pending hashed work") Signed-off-by: Nicholas Carlini 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 @@ -1034,7 +1034,8 @@ static inline void io_wqe_remove_pending if (io_wq_is_hashed(work) && work == wqe->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) wqe->hash_tail[hash] = prev_work; else wqe->hash_tail[hash] = NULL;