Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759452AbcCDJ2t (ORCPT ); Fri, 4 Mar 2016 04:28:49 -0500 Received: from mx2.suse.de ([195.135.220.15]:59714 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758988AbcCDJDU (ORCPT ); Fri, 4 Mar 2016 04:03:20 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Nicholas Bellinger , Sagi Grimberg , Jiri Slaby Subject: [PATCH 3.12 059/116] target: Fix race for SCF_COMPARE_AND_WRITE_POST checking Date: Fri, 4 Mar 2016 10:01:44 +0100 Message-Id: X-Mailer: git-send-email 2.7.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5347 Lines: 137 From: Nicholas Bellinger 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 057085e522f8bf94c2e691a5b76880f68060f8ba upstream. This patch addresses a race + use after free where the first stage of COMPARE_AND_WRITE in compare_and_write_callback() is rescheduled after the backend sends the secondary WRITE, resulting in second stage compare_and_write_post() callback completing in target_complete_ok_work() before the first can return. Because current code depends on checking se_cmd->se_cmd_flags after return from se_cmd->transport_complete_callback(), this results in first stage having SCF_COMPARE_AND_WRITE_POST set, which incorrectly falls through into second stage CAW processing code, eventually triggering a NULL pointer dereference due to use after free. To address this bug, pass in a new *post_ret parameter into se_cmd->transport_complete_callback(), and depend upon this value instead of ->se_cmd_flags to determine when to return or fall through into ->queue_status() code for CAW. Cc: Sagi Grimberg Signed-off-by: Nicholas Bellinger Signed-off-by: Jiri Slaby --- drivers/target/target_core_sbc.c | 13 +++++++++---- drivers/target/target_core_transport.c | 14 ++++++++------ include/target/target_core_base.h | 2 +- 3 files changed, 18 insertions(+), 11 deletions(-) diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c index 75f126538a72..6e60ab250f55 100644 --- a/drivers/target/target_core_sbc.c +++ b/drivers/target/target_core_sbc.c @@ -298,7 +298,8 @@ sbc_setup_write_same(struct se_cmd *cmd, unsigned char *flags, struct sbc_ops *o return 0; } -static sense_reason_t xdreadwrite_callback(struct se_cmd *cmd, bool success) +static sense_reason_t xdreadwrite_callback(struct se_cmd *cmd, bool success, + int *post_ret) { unsigned char *buf, *addr; struct scatterlist *sg; @@ -362,7 +363,8 @@ sbc_execute_rw(struct se_cmd *cmd) cmd->data_direction); } -static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success) +static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success, + int *post_ret) { struct se_device *dev = cmd->se_dev; @@ -372,8 +374,10 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success) * sent to the backend driver. */ spin_lock_irq(&cmd->t_state_lock); - if ((cmd->transport_state & CMD_T_SENT) && !cmd->scsi_status) + if ((cmd->transport_state & CMD_T_SENT) && !cmd->scsi_status) { cmd->se_cmd_flags |= SCF_COMPARE_AND_WRITE_POST; + *post_ret = 1; + } spin_unlock_irq(&cmd->t_state_lock); /* @@ -385,7 +389,8 @@ static sense_reason_t compare_and_write_post(struct se_cmd *cmd, bool success) return TCM_NO_SENSE; } -static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success) +static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool success, + int *post_ret) { struct se_device *dev = cmd->se_dev; struct scatterlist *write_sg = NULL, *sg; diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c index b52bf3cad494..b335709f050f 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -1570,7 +1570,7 @@ bool target_stop_cmd(struct se_cmd *cmd, unsigned long *flags) void transport_generic_request_failure(struct se_cmd *cmd, sense_reason_t sense_reason) { - int ret = 0; + int ret = 0, post_ret = 0; pr_debug("-----[ Storage Engine Exception for cmd: %p ITT: 0x%08x" " CDB: 0x%02x\n", cmd, cmd->se_tfo->get_task_tag(cmd), @@ -1593,7 +1593,7 @@ void transport_generic_request_failure(struct se_cmd *cmd, */ if ((cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) && cmd->transport_complete_callback) - cmd->transport_complete_callback(cmd, false); + cmd->transport_complete_callback(cmd, false, &post_ret); switch (sense_reason) { case TCM_NON_EXISTENT_LUN: @@ -1941,11 +1941,13 @@ static void target_complete_ok_work(struct work_struct *work) */ if (cmd->transport_complete_callback) { sense_reason_t rc; + bool caw = (cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE); + bool zero_dl = !(cmd->data_length); + int post_ret = 0; - rc = cmd->transport_complete_callback(cmd, true); - if (!rc && !(cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE_POST)) { - if ((cmd->se_cmd_flags & SCF_COMPARE_AND_WRITE) && - !cmd->data_length) + rc = cmd->transport_complete_callback(cmd, true, &post_ret); + if (!rc && !post_ret) { + if (caw && zero_dl) goto queue_rsp; return; diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 085e6bedf393..5c5700bd1345 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -457,7 +457,7 @@ struct se_cmd { sense_reason_t (*execute_cmd)(struct se_cmd *); sense_reason_t (*execute_rw)(struct se_cmd *, struct scatterlist *, u32, enum dma_data_direction); - sense_reason_t (*transport_complete_callback)(struct se_cmd *, bool); + sense_reason_t (*transport_complete_callback)(struct se_cmd *, bool, int *); unsigned char *t_task_cdb; unsigned char __t_task_cdb[TCM_MAX_COMMAND_SIZE]; -- 2.7.2