From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59BBCC43381 for ; Wed, 13 Mar 2019 19:17:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21D80213A2 for ; Wed, 13 Mar 2019 19:17:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552504629; bh=LC8+0NSKM2PdnlAhgKXO3km7DorsxRTeStsNSMrtj3U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=t2kbmHm2qwA4s/sysWDbyGzyD6m0YJjuqvXV0gQIOVUvWiz8lQ7/n1j1udn2REAFa +AQ4QU9aJvw59WovBoxoyGZNJUWTDkT9qNlC5Vbb8QJyrX9No5WajwJx2Jc1zOD3Wc 2Hrsr7P7sgWWlErE9uw3Yk898ibxthglJFF3FrwE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728829AbfCMTRH (ORCPT ); Wed, 13 Mar 2019 15:17:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:47452 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727545AbfCMTRE (ORCPT ); Wed, 13 Mar 2019 15:17:04 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 661242075C; Wed, 13 Mar 2019 19:17:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552504623; bh=LC8+0NSKM2PdnlAhgKXO3km7DorsxRTeStsNSMrtj3U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uNIaHUlX1b3QYsPwPXzzdAfwAsIctkrij/pR01Y6ColAzOj3y2y+TZ7wVxjSu5yPH i1xmAOZcx4olPkbaMAQkYTTpUiLcOGH1NmzFaPzKqTortfuzRN5jV/bnQDmQoIK8uP IXbyd42KBYYWA0bw3/7Nom5IlMIVe6nOkalZByn0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Anoob Soman , Bob Liu , "Martin K . Petersen" , Sasha Levin , open-iscsi@googlegroups.com, linux-scsi@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 04/24] scsi: libiscsi: Fix race between iscsi_xmit_task and iscsi_complete_task Date: Wed, 13 Mar 2019 15:16:27 -0400 Message-Id: <20190313191647.160171-4-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190313191647.160171-1-sashal@kernel.org> References: <20190313191647.160171-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anoob Soman [ Upstream commit 79edd00dc6a96644d76b4a1cb97d94d49e026768 ] When a target sends Check Condition, whilst initiator is busy xmiting re-queued data, could lead to race between iscsi_complete_task() and iscsi_xmit_task() and eventually crashing with the following kernel backtrace. [3326150.987523] ALERT: BUG: unable to handle kernel NULL pointer dereference at 0000000000000078 [3326150.987549] ALERT: IP: [] iscsi_xmit_task+0x2d/0xc0 [libiscsi] [3326150.987571] WARN: PGD 569c8067 PUD 569c9067 PMD 0 [3326150.987582] WARN: Oops: 0002 [#1] SMP [3326150.987593] WARN: Modules linked in: tun nfsv3 nfs fscache dm_round_robin [3326150.987762] WARN: CPU: 2 PID: 8399 Comm: kworker/u32:1 Tainted: G O 4.4.0+2 #1 [3326150.987774] WARN: Hardware name: Dell Inc. PowerEdge R720/0W7JN5, BIOS 2.5.4 01/22/2016 [3326150.987790] WARN: Workqueue: iscsi_q_13 iscsi_xmitworker [libiscsi] [3326150.987799] WARN: task: ffff8801d50f3800 ti: ffff8801f5458000 task.ti: ffff8801f5458000 [3326150.987810] WARN: RIP: e030:[] [] iscsi_xmit_task+0x2d/0xc0 [libiscsi] [3326150.987825] WARN: RSP: e02b:ffff8801f545bdb0 EFLAGS: 00010246 [3326150.987831] WARN: RAX: 00000000ffffffc3 RBX: ffff880282d2ab20 RCX: ffff88026b6ac480 [3326150.987842] WARN: RDX: 0000000000000000 RSI: 00000000fffffe01 RDI: ffff880282d2ab20 [3326150.987852] WARN: RBP: ffff8801f545bdc8 R08: 0000000000000000 R09: 0000000000000008 [3326150.987862] WARN: R10: 0000000000000000 R11: 000000000000fe88 R12: 0000000000000000 [3326150.987872] WARN: R13: ffff880282d2abe8 R14: ffff880282d2abd8 R15: ffff880282d2ac08 [3326150.987890] WARN: FS: 00007f5a866b4840(0000) GS:ffff88028a640000(0000) knlGS:0000000000000000 [3326150.987900] WARN: CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033 [3326150.987907] WARN: CR2: 0000000000000078 CR3: 0000000070244000 CR4: 0000000000042660 [3326150.987918] WARN: Stack: [3326150.987924] WARN: ffff880282d2ad58 ffff880282d2ab20 ffff880282d2abe8 ffff8801f545be18 [3326150.987938] WARN: ffffffffa05cea90 ffff880282d2abf8 ffff88026b59cc80 ffff88026b59cc00 [3326150.987951] WARN: ffff88022acf32c0 ffff880289491800 ffff880255a80800 0000000000000400 [3326150.987964] WARN: Call Trace: [3326150.987975] WARN: [] iscsi_xmitworker+0x2f0/0x360 [libiscsi] [3326150.987988] WARN: [] process_one_work+0x1fc/0x3b0 [3326150.987997] WARN: [] worker_thread+0x2a5/0x470 [3326150.988006] WARN: [] ? __schedule+0x648/0x870 [3326150.988015] WARN: [] ? rescuer_thread+0x300/0x300 [3326150.988023] WARN: [] kthread+0xd5/0xe0 [3326150.988031] WARN: [] ? kthread_stop+0x110/0x110 [3326150.988040] WARN: [] ret_from_fork+0x3f/0x70 [3326150.988048] WARN: [] ? kthread_stop+0x110/0x110 [3326150.988127] ALERT: RIP [] iscsi_xmit_task+0x2d/0xc0 [libiscsi] [3326150.988138] WARN: RSP [3326150.988144] WARN: CR2: 0000000000000078 [3326151.020366] WARN: ---[ end trace 1c60974d4678d81b ]--- Commit 6f8830f5bbab ("scsi: libiscsi: add lock around task lists to fix list corruption regression") introduced "taskqueuelock" to fix list corruption during the race, but this wasn't enough. Re-setting of conn->task to NULL, could race with iscsi_xmit_task(). iscsi_complete_task() { .... if (conn->task == task) conn->task = NULL; } conn->task in iscsi_xmit_task() could be NULL and so will be task. __iscsi_get_task(task) will crash (NullPtr de-ref), trying to access refcount. iscsi_xmit_task() { struct iscsi_task *task = conn->task; __iscsi_get_task(task); } This commit will take extra conn->session->back_lock in iscsi_xmit_task() to ensure iscsi_xmit_task() waits for iscsi_complete_task(), if iscsi_complete_task() wins the race. If iscsi_xmit_task() wins the race, iscsi_xmit_task() increments task->refcount (__iscsi_get_task) ensuring iscsi_complete_task() will not iscsi_free_task(). Signed-off-by: Anoob Soman Signed-off-by: Bob Liu Acked-by: Lee Duncan Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/scsi/libiscsi.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c index c79743de48f9..2ffe10453e30 100644 --- a/drivers/scsi/libiscsi.c +++ b/drivers/scsi/libiscsi.c @@ -1448,7 +1448,13 @@ static int iscsi_xmit_task(struct iscsi_conn *conn) if (test_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx)) return -ENODATA; + spin_lock_bh(&conn->session->back_lock); + if (conn->task == NULL) { + spin_unlock_bh(&conn->session->back_lock); + return -ENODATA; + } __iscsi_get_task(task); + spin_unlock_bh(&conn->session->back_lock); spin_unlock_bh(&conn->session->frwd_lock); rc = conn->session->tt->xmit_task(task); spin_lock_bh(&conn->session->frwd_lock); -- 2.19.1