From patchwork Wed Dec 6 00:57:51 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 10094553 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 2D3E360329 for ; Wed, 6 Dec 2017 00:58:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1EB4528C30 for ; Wed, 6 Dec 2017 00:58:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0E90528CD2; Wed, 6 Dec 2017 00:58:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A10B628CD1 for ; Wed, 6 Dec 2017 00:58:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753887AbdLFA6C (ORCPT ); Tue, 5 Dec 2017 19:58:02 -0500 Received: from esa4.hgst.iphmx.com ([216.71.154.42]:21752 "EHLO esa4.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753406AbdLFA5z (ORCPT ); Tue, 5 Dec 2017 19:57:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=wdc.com; i=@wdc.com; q=dns/txt; s=dkim.wdc.com; t=1512521876; x=1544057876; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=cQMhKEyF4JsN/7CG+AfO65ZUNiawRZbZ008g2xcKH5A=; b=InjqupBuFf8Bkl+Ncy/3y2zxFMCy1WaBlXpLK+7YPC5ojm4SjHyY2v6l vsOuslVYmhasZ7nQTQeXlsdE+bYngmG0CNYbEWX1UI7knzd6IFOsFdo6T ZVFWVs6OA0I9cucD5wMjRPJPl3ho9Z9qLrOjyY0z3RGc6ihe1RtFWQutY mx1nyj7XApShVaPoDbJVBqZw8wWh4wk8+ZSeclw3+8AYcyEv2lRuioWN4 MxeafXc+ew+msE6CULV5djbMnQZPgADptB4xN+UzOqabB68nrr7A8uID8 ENlmciU7YlHHTYAUAjt+pPuKqENdYyQi+SipTHiNP9RR3trAYP26ocdQ8 Q==; X-IronPort-AV: E=Sophos;i="5.45,366,1508774400"; d="scan'208";a="64068919" Received: from uls-op-cesaip01.wdc.com (HELO uls-op-cesaep01.wdc.com) ([199.255.45.14]) by ob1.hgst.iphmx.com with ESMTP; 06 Dec 2017 08:57:55 +0800 Received: from uls-op-cesaip02.wdc.com ([10.248.3.37]) by uls-op-cesaep01.wdc.com with ESMTP; 05 Dec 2017 16:55:03 -0800 Received: from thinkpad-bart.sdcorp.global.sandisk.com (HELO thinkpad-bart.int.fusionio.com) ([10.11.166.51]) by uls-op-cesaip02.wdc.com with ESMTP; 05 Dec 2017 16:57:55 -0800 From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, Christoph Hellwig , Bart Van Assche , "James E . J . Bottomley" , "Martin K . Petersen" , Ming Lei , Hannes Reinecke , Johannes Thumshirn , stable@vger.kernel.org Subject: [PATCH v2 1/3] scsi: Fix a scsi_show_rq() NULL pointer dereference Date: Tue, 5 Dec 2017 16:57:51 -0800 Message-Id: <20171206005753.28734-2-bart.vanassche@wdc.com> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171206005753.28734-1-bart.vanassche@wdc.com> References: <20171206005753.28734-1-bart.vanassche@wdc.com> Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Avoid that scsi_show_rq() triggers a NULL pointer dereference if called after sd_uninit_command(). Swap the NULL pointer assignment and the mempool_free() call in sd_uninit_command() to make it less likely that scsi_show_rq() triggers a use-after-free. Note: even with these changes scsi_show_rq() can trigger a use-after-free but that's a lesser evil than e.g. suppressing debug information for T10-PI commands completely. This patch fixes the following oops: BUG: unable to handle kernel NULL pointer dereference at (null) IP: scsi_format_opcode_name+0x1a/0x1c0 CPU: 1 PID: 1881 Comm: cat Not tainted 4.14.0-rc2.blk_mq_io_hang+ #516 Call Trace: __scsi_format_command+0x27/0xc0 scsi_show_rq+0x5c/0xc0 __blk_mq_debugfs_rq_show+0x116/0x130 blk_mq_debugfs_rq_show+0xe/0x10 seq_read+0xfe/0x3b0 full_proxy_read+0x54/0x90 __vfs_read+0x37/0x160 vfs_read+0x96/0x130 SyS_read+0x55/0xc0 entry_SYSCALL_64_fastpath+0x1a/0xa5 Fixes: 0eebd005dd07 ("scsi: Implement blk_mq_ops.show_rq()") Reported-by: Ming Lei Signed-off-by: Bart Van Assche Cc: James E.J. Bottomley Cc: Martin K. Petersen Cc: Ming Lei Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: stable@vger.kernel.org --- drivers/scsi/scsi_debugfs.c | 6 ++++-- drivers/scsi/sd.c | 4 +++- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/scsi_debugfs.c b/drivers/scsi/scsi_debugfs.c index 01f08c03f2c1..c3765d29fd3f 100644 --- a/drivers/scsi/scsi_debugfs.c +++ b/drivers/scsi/scsi_debugfs.c @@ -8,9 +8,11 @@ void scsi_show_rq(struct seq_file *m, struct request *rq) { struct scsi_cmnd *cmd = container_of(scsi_req(rq), typeof(*cmd), req); int msecs = jiffies_to_msecs(jiffies - cmd->jiffies_at_alloc); - char buf[80]; + const u8 *const cdb = READ_ONCE(cmd->cmnd); + char buf[80] = "(?)"; - __scsi_format_command(buf, sizeof(buf), cmd->cmnd, cmd->cmd_len); + if (cdb) + __scsi_format_command(buf, sizeof(buf), cdb, cmd->cmd_len); seq_printf(m, ", .cmd=%s, .retries=%d, allocated %d.%03d s ago", buf, cmd->retries, msecs / 1000, msecs % 1000); } diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index d175c5c5ccf8..d841743b2107 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1284,6 +1284,7 @@ static int sd_init_command(struct scsi_cmnd *cmd) static void sd_uninit_command(struct scsi_cmnd *SCpnt) { struct request *rq = SCpnt->request; + u8 *cmnd; if (SCpnt->flags & SCMD_ZONE_WRITE_LOCK) sd_zbc_write_unlock_zone(SCpnt); @@ -1292,9 +1293,10 @@ static void sd_uninit_command(struct scsi_cmnd *SCpnt) __free_page(rq->special_vec.bv_page); if (SCpnt->cmnd != scsi_req(rq)->cmd) { - mempool_free(SCpnt->cmnd, sd_cdb_pool); + cmnd = SCpnt->cmnd; SCpnt->cmnd = NULL; SCpnt->cmd_len = 0; + mempool_free(cmnd, sd_cdb_pool); } }