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authorNicholas Bellinger <nab@linux-iscsi.org>2015-11-05 23:37:59 -0800
committerNicholas Bellinger <nab@linux-iscsi.org>2015-11-28 19:33:15 -0800
commit057085e522f8bf94c2e691a5b76880f68060f8ba (patch)
treed813e53ee7853a19eb2697e71bd2851b8acc5cc6
parentca82c2bded29b38d36140bfa1e76a7bbfcade390 (diff)
downloadlwn-057085e522f8bf94c2e691a5b76880f68060f8ba.tar.gz
lwn-057085e522f8bf94c2e691a5b76880f68060f8ba.zip
target: Fix race for SCF_COMPARE_AND_WRITE_POST checking
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@mellanox.com> Cc: <stable@vger.kernel.org> # v3.12+ Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
-rw-r--r--drivers/target/target_core_sbc.c13
-rw-r--r--drivers/target/target_core_transport.c14
-rw-r--r--include/target/target_core_base.h2
3 files changed, 18 insertions, 11 deletions
diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index 0b4b2a67d9f9..ae24d0fdcd76 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 5bacc7b5ed6d..010b8c46f1ef 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 0a2c74008e53..aabf0aca0171 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;