From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
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 <sagig@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.12+
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
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 0b4b2a6..ae24d0f 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -371,7 +371,8 @@ 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;
@@ -437,7 +438,8 @@ 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;
@@ -447,8 +449,10 @@ 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);
/*
@@ -460,7 +464,8 @@ 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 5bacc7b..010b8c4 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1658,7 +1658,7 @@ 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%08llx"
" CDB: 0x%02x\n", cmd, cmd->tag, cmd->t_task_cdb[0]);
@@ -1680,7 +1680,7 @@ 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:
@@ -2068,11 +2068,13 @@ 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 8b9c727..61a0393 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -474,7 +474,7 @@ struct se_cmd {
struct completion cmd_wait_comp;
const struct target_core_fabric_ops *se_tfo;
sense_reason_t (*execute_cmd)(struct se_cmd *);
- sense_reason_t (*transport_complete_callback)(struct se_cmd *, bool);
+ sense_reason_t (*transport_complete_callback)(struct se_cmd *, bool, int *);
void *protocol_data;
unsigned char *t_task_cdb;
--
1.9.1
--
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