Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935928AbdLRQL4 (ORCPT ); Mon, 18 Dec 2017 11:11:56 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:42456 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933651AbdLRQLt (ORCPT ); Mon, 18 Dec 2017 11:11:49 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ming Lei , Bart Van Assche , "James E.J. Bottomley" , "Martin K. Petersen" , Christoph Hellwig , Hannes Reinecke , Johannes Thumshirn Subject: [PATCH 4.14 031/178] scsi: core: Fix a scsi_show_rq() NULL pointer dereference Date: Mon, 18 Dec 2017 16:47:47 +0100 Message-Id: <20171218152921.851263159@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171218152920.567991776@linuxfoundation.org> References: <20171218152920.567991776@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3069 Lines: 89 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bart Van Assche commit 14e3062fb18532175af4d1c4073597999f7a2248 upstream. 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 Type 2 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 [mkp: added Type 2] 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 Signed-off-by: Martin K. Petersen Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/scsi_debugfs.c | 6 ++++-- drivers/scsi/sd.c | 4 +++- 2 files changed, 7 insertions(+), 3 deletions(-) --- a/drivers/scsi/scsi_debugfs.c +++ b/drivers/scsi/scsi_debugfs.c @@ -8,9 +8,11 @@ void scsi_show_rq(struct seq_file *m, st { 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); } --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1284,6 +1284,7 @@ static int sd_init_command(struct scsi_c 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 scs __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); } }