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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 516A6C7618F for ; Mon, 15 Jul 2019 15:03:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2A48B2067C for ; Mon, 15 Jul 2019 15:03:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563203008; bh=oLaZZsiAsWPg5tIXJ0siM1ZrBH71h7yIil+f0MEhA/0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=OLKwpP5WCqsEEZcxGCXi5eXYpj961rMf00XQkvIh6N7+N3h7A6LH/+tByi04+xWE+ OqFWnMzHFVnTHDyQm4DOUPL06otPwvnljGuoFdrzxHyab4/DHNcrY6UNumI61EIBt6 gUpsBlC4hOq1L/ar1vvtYlcK7234lXJJytVVxRJs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388242AbfGOOJO (ORCPT ); Mon, 15 Jul 2019 10:09:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:60582 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731241AbfGOOJL (ORCPT ); Mon, 15 Jul 2019 10:09:11 -0400 Received: from sasha-vm.mshome.net (unknown [73.61.17.35]) (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 E146521841; Mon, 15 Jul 2019 14:09:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563199751; bh=oLaZZsiAsWPg5tIXJ0siM1ZrBH71h7yIil+f0MEhA/0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YUlHdat+StXVRr4EVSI9D7P4RSI+S1pV8JPq0Gb5pWess+IrJWyWDTsbtMheKgIM4 YJfxUq1jK1VCXn8T8c/RILiJfXVYhOAMrrJtXi5EcRnlhFuuLriboJEcfyXz62S44s FSxRQis1W4XasL6fRFw+G3R2Qvs32V/rPsRQBMvQ= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Bob Liu , Jens Axboe , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 5.1 095/219] block: null_blk: fix race condition for null_del_dev Date: Mon, 15 Jul 2019 10:01:36 -0400 Message-Id: <20190715140341.6443-95-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190715140341.6443-1-sashal@kernel.org> References: <20190715140341.6443-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Bob Liu [ Upstream commit 7602843fd873cae43a444b83b14dfdd114a9659c ] Dulicate call of null_del_dev() will trigger null pointer error like below. The reason is a race condition between nullb_device_power_store() and nullb_group_drop_item(). CPU#0 CPU#1 ---------------- ----------------- do_rmdir() >configfs_rmdir() >client_drop_item() >nullb_group_drop_item() nullb_device_power_store() >null_del_dev() >test_and_clear_bit(NULLB_DEV_FL_UP >null_del_dev() ^^^^^ Duplicated null_dev_dev() triger null pointer error >clear_bit(NULLB_DEV_FL_UP The fix could be keep the sequnce of clear NULLB_DEV_FL_UP and null_del_dev(). [ 698.613600] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 698.613608] #PF error: [normal kernel read fault] [ 698.613611] PGD 0 P4D 0 [ 698.613619] Oops: 0000 [#1] SMP PTI [ 698.613627] CPU: 3 PID: 6382 Comm: rmdir Not tainted 5.0.0+ #35 [ 698.613631] Hardware name: LENOVO 20LJS2EV08/20LJS2EV08, BIOS R0SET33W (1.17 ) 07/18/2018 [ 698.613644] RIP: 0010:null_del_dev+0xc/0x110 [null_blk] [ 698.613649] Code: 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b eb 97 e8 47 bb 2a e8 0f 1f 80 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 54 53 <8b> 77 18 48 89 fb 4c 8b 27 48 c7 c7 40 57 1e c1 e8 bf c7 cb e8 48 [ 698.613654] RSP: 0018:ffffb887888bfde0 EFLAGS: 00010286 [ 698.613659] RAX: 0000000000000000 RBX: ffff9d436d92bc00 RCX: ffff9d43a9184681 [ 698.613663] RDX: ffffffffc11e5c30 RSI: 0000000068be6540 RDI: 0000000000000000 [ 698.613667] RBP: ffffb887888bfdf0 R08: 0000000000000001 R09: 0000000000000000 [ 698.613671] R10: ffffb887888bfdd8 R11: 0000000000000f16 R12: ffff9d436d92bc08 [ 698.613675] R13: ffff9d436d94e630 R14: ffffffffc11e5088 R15: ffffffffc11e5000 [ 698.613680] FS: 00007faa68be6540(0000) GS:ffff9d43d14c0000(0000) knlGS:0000000000000000 [ 698.613685] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 698.613689] CR2: 0000000000000018 CR3: 000000042f70c002 CR4: 00000000003606e0 [ 698.613693] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 698.613697] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 698.613700] Call Trace: [ 698.613712] nullb_group_drop_item+0x50/0x70 [null_blk] [ 698.613722] client_drop_item+0x29/0x40 [ 698.613728] configfs_rmdir+0x1ed/0x300 [ 698.613738] vfs_rmdir+0xb2/0x130 [ 698.613743] do_rmdir+0x1c7/0x1e0 [ 698.613750] __x64_sys_rmdir+0x17/0x20 [ 698.613759] do_syscall_64+0x5a/0x110 [ 698.613768] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Signed-off-by: Bob Liu Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/block/null_blk_main.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c index d7ac09c092f2..21d0b651b335 100644 --- a/drivers/block/null_blk_main.c +++ b/drivers/block/null_blk_main.c @@ -326,11 +326,12 @@ static ssize_t nullb_device_power_store(struct config_item *item, set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags); dev->power = newp; } else if (dev->power && !newp) { - mutex_lock(&lock); - dev->power = newp; - null_del_dev(dev->nullb); - mutex_unlock(&lock); - clear_bit(NULLB_DEV_FL_UP, &dev->flags); + if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) { + mutex_lock(&lock); + dev->power = newp; + null_del_dev(dev->nullb); + mutex_unlock(&lock); + } clear_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags); } -- 2.20.1