From 5dd73bb38031a5d8f81bf7d9b4f10135ab950f64 Mon Sep 17 00:00:00 2001 From: Nicholas Bellinger Date: Sun, 6 Mar 2016 01:24:23 +0000 Subject: [PATCH] target: Fix race for SCF_COMPARE_AND_WRITE_POST checking [ Upstream commit 057085e522f8bf94c2e691a5b76880f68060f8ba ] 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: Sasha Levin --- 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 733824e..a3bfafc 100644 --- a/drivers/target/target_core_sbc.c +++ b/drivers/target/target_core_sbc.c @@ -321,7 +321,8 @@ 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; @@ -385,7 +386,8 @@ 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; @@ -395,8 +397,10 @@ 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); /* @@ -408,7 +412,8 @@ 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 3881504..316de3f 100644 --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -1638,7 +1638,7 @@ 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), @@ -1661,7 +1661,7 @@ 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: @@ -2056,11 +2056,13 @@ 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 480e9f8..b7a0594 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -522,7 +522,7 @@ 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]; -- 2.7.4