From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
This patch fixes a NULL pointer se_cmd->cmd_kref < 0
refcount bug during TMR LUN_RESET with active se_cmd
I/O, that can be triggered during se_cmd descriptor
shutdown + release via core_tmr_drain_state_list() code.
To address this bug, add common __target_check_io_state()
helper for ABORT_TASK + LUN_RESET w/ CMD_T_COMPLETE
checking, and set CMD_T_ABORTED + obtain ->cmd_kref for
both cases ahead of last target_put_sess_cmd() after
TFO->aborted_task() -> transport_cmd_finish_abort()
callback has completed.
It also introduces SCF_ACK_KREF to determine when
transport_cmd_finish_abort() needs to drop the second
extra reference, ahead of calling target_put_sess_cmd()
for the final kref_put(&se_cmd->cmd_kref).
It also updates transport_cmd_check_stop() to avoid
holding se_cmd->t_state_lock while dropping se_cmd
device state via target_remove_from_state_list(), now
that core_tmr_drain_state_list() is holding the
se_device lock while checking se_cmd state from
within TMR logic.
Finally, move transport_put_cmd() release of SGL +
TMR + extended CDB memory into target_free_cmd_mem()
in order to avoid potential resource leaks in TMR
ABORT_TASK + LUN_RESET code-paths. Also update
target_release_cmd_kref() accordingly.
Cc: Quinn Tran <quinn.tran@xxxxxxxxxx>
Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Andy Grover <agrover@xxxxxxxxxx>
Cc: Mike Christie <mchristi@xxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_tmr.c | 66 ++++++++++++++++++++++++----------
drivers/target/target_core_transport.c | 56 ++++++++++++++---------------
include/target/target_core_base.h | 1 +
3 files changed, 75 insertions(+), 48 deletions(-)
diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index 7137042..5f315b4 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -107,6 +107,34 @@ static int target_check_cdb_and_preempt(struct list_head *list,
return 1;
}
+static bool __target_check_io_state(struct se_cmd *se_cmd)
+{
+ struct se_session *sess = se_cmd->se_sess;
+
+ assert_spin_locked(&se_session->sess_cmd_lock);
+ WARN_ON_ONCE(!irqs_disabled());
+ /*
+ * If command already reached CMD_T_COMPLETE state within
+ * target_complete_cmd(), this se_cmd has been passed to
+ * fabric driver and will not be aborted.
+ *
+ * Otherwise, obtain a local se_cmd->cmd_kref now for TMR
+ * ABORT_TASK + LUN_RESET for CMD_T_ABORTED processing as
+ * long as se_cmd->cmd_kref is still active unless zero.
+ */
+ spin_lock(&se_cmd->t_state_lock);
+ if (se_cmd->transport_state & CMD_T_COMPLETE) {
+ pr_debug("Attempted to abort io tag: %llu already complete,"
+ " skipping\n", se_cmd->tag);
+ spin_unlock(&se_cmd->t_state_lock);
+ return false;
+ }
+ se_cmd->transport_state |= CMD_T_ABORTED;
+ spin_unlock(&se_cmd->t_state_lock);
+
+ return kref_get_unless_zero(&se_cmd->cmd_kref);
+}
+
void core_tmr_abort_task(
struct se_device *dev,
struct se_tmr_req *tmr,
@@ -133,26 +161,18 @@ void core_tmr_abort_task(
printk("ABORT_TASK: Found referenced %s task_tag: %llu\n",
se_cmd->se_tfo->get_fabric_name(), ref_tag);
- spin_lock(&se_cmd->t_state_lock);
- if (se_cmd->transport_state & CMD_T_COMPLETE) {
- printk("ABORT_TASK: ref_tag: %llu already complete,"
- " skipping\n", ref_tag);
- spin_unlock(&se_cmd->t_state_lock);
+ if (!__target_check_io_state(se_cmd)) {
spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
goto out;
}
- se_cmd->transport_state |= CMD_T_ABORTED;
- spin_unlock(&se_cmd->t_state_lock);
-
list_del_init(&se_cmd->se_cmd_list);
- kref_get(&se_cmd->cmd_kref);
spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
cancel_work_sync(&se_cmd->work);
transport_wait_for_tasks(se_cmd);
- target_put_sess_cmd(se_cmd);
transport_cmd_finish_abort(se_cmd, true);
+ target_put_sess_cmd(se_cmd);
printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
" ref_tag: %llu\n", ref_tag);
@@ -237,8 +257,10 @@ static void core_tmr_drain_state_list(
struct list_head *preempt_and_abort_list)
{
LIST_HEAD(drain_task_list);
+ struct se_session *sess;
struct se_cmd *cmd, *next;
unsigned long flags;
+ int rc;
/*
* Complete outstanding commands with TASK_ABORTED SAM status.
@@ -277,6 +299,17 @@ static void core_tmr_drain_state_list(
if (prout_cmd == cmd)
continue;
+ sess = cmd->se_sess;
+ if (WARN_ON_ONCE(!sess))
+ continue;
+
+ spin_lock(&sess->sess_cmd_lock);
+ rc = __target_check_io_state(cmd);
+ spin_unlock(&sess->sess_cmd_lock);
+ if (!rc) {
+ printk("LUN_RESET I/O: non-zero kref_get_unless_zero\n");
+ continue;
+ }
list_move_tail(&cmd->state_list, &drain_task_list);
cmd->state_active = false;
}
@@ -284,7 +317,7 @@ static void core_tmr_drain_state_list(
while (!list_empty(&drain_task_list)) {
cmd = list_entry(drain_task_list.next, struct se_cmd, state_list);
- list_del(&cmd->state_list);
+ list_del_init(&cmd->state_list);
pr_debug("LUN_RESET: %s cmd: %p"
" ITT/CmdSN: 0x%08llx/0x%08x, i_state: %d, t_state: %d"
@@ -308,16 +341,11 @@ static void core_tmr_drain_state_list(
* loop above, but we do it down here given that
* cancel_work_sync may block.
*/
- if (cmd->t_state == TRANSPORT_COMPLETE)
- cancel_work_sync(&cmd->work);
-
- spin_lock_irqsave(&cmd->t_state_lock, flags);
- target_stop_cmd(cmd, &flags);
-
- cmd->transport_state |= CMD_T_ABORTED;
- spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+ cancel_work_sync(&cmd->work);
+ transport_wait_for_tasks(cmd);
core_tmr_handle_tas_abort(tmr_nacl, cmd, tas);
+ target_put_sess_cmd(cmd);
}
}
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index a7c1bb5..19500e3 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -561,10 +561,6 @@ static int transport_cmd_check_stop(struct se_cmd *cmd, bool remove_from_lists,
{
unsigned long flags;
- spin_lock_irqsave(&cmd->t_state_lock, flags);
- if (write_pending)
- cmd->t_state = TRANSPORT_WRITE_PENDING;
-
if (remove_from_lists) {
target_remove_from_state_list(cmd);
@@ -574,6 +570,10 @@ static int transport_cmd_check_stop(struct se_cmd *cmd, bool remove_from_lists,
cmd->se_lun = NULL;
}
+ spin_lock_irqsave(&cmd->t_state_lock, flags);
+ if (write_pending)
+ cmd->t_state = TRANSPORT_WRITE_PENDING;
+
/*
* Determine if frontend context caller is requesting the stopping of
* this command for frontend exceptions.
@@ -627,6 +627,8 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
{
+ bool ack_kref = (cmd->se_cmd_flags & SCF_ACK_KREF);
+
if (cmd->se_cmd_flags & SCF_SE_LUN_CMD)
transport_lun_remove_cmd(cmd);
/*
@@ -638,7 +640,7 @@ void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
if (transport_cmd_check_stop_to_fabric(cmd))
return;
- if (remove)
+ if (remove && ack_kref)
transport_put_cmd(cmd);
}
@@ -706,7 +708,7 @@ void target_complete_cmd(struct se_cmd *cmd, u8 scsi_status)
* Check for case where an explicit ABORT_TASK has been received
* and transport_wait_for_tasks() will be waiting for completion..
*/
- if (cmd->transport_state & CMD_T_ABORTED &&
+ if (cmd->transport_state & CMD_T_ABORTED ||
cmd->transport_state & CMD_T_STOP) {
spin_unlock_irqrestore(&cmd->t_state_lock, flags);
complete_all(&cmd->t_transport_stop_comp);
@@ -2220,20 +2222,14 @@ static inline void transport_free_pages(struct se_cmd *cmd)
}
/**
- * transport_release_cmd - free a command
- * @cmd: command to free
+ * transport_put_cmd - release a reference to a command
+ * @cmd: command to release
*
- * This routine unconditionally frees a command, and reference counting
- * or list removal must be done in the caller.
+ * This routine releases our reference to the command and frees it if possible.
*/
-static int transport_release_cmd(struct se_cmd *cmd)
+static int transport_put_cmd(struct se_cmd *cmd)
{
BUG_ON(!cmd->se_tfo);
-
- if (cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
- core_tmr_release_req(cmd->se_tmr_req);
- if (cmd->t_task_cdb != cmd->__t_task_cdb)
- kfree(cmd->t_task_cdb);
/*
* If this cmd has been setup with target_get_sess_cmd(), drop
* the kref and call ->release_cmd() in kref callback.
@@ -2241,18 +2237,6 @@ static int transport_release_cmd(struct se_cmd *cmd)
return target_put_sess_cmd(cmd);
}
-/**
- * transport_put_cmd - release a reference to a command
- * @cmd: command to release
- *
- * This routine releases our reference to the command and frees it if possible.
- */
-static int transport_put_cmd(struct se_cmd *cmd)
-{
- transport_free_pages(cmd);
- return transport_release_cmd(cmd);
-}
-
void *transport_kmap_data_sg(struct se_cmd *cmd)
{
struct scatterlist *sg = cmd->t_data_sg;
@@ -2457,7 +2441,7 @@ int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
if (wait_for_tasks && (cmd->se_cmd_flags & SCF_SCSI_TMR_CDB))
transport_wait_for_tasks(cmd);
- ret = transport_release_cmd(cmd);
+ ret = transport_put_cmd(cmd);
} else {
if (wait_for_tasks)
transport_wait_for_tasks(cmd);
@@ -2515,6 +2499,16 @@ out:
}
EXPORT_SYMBOL(target_get_sess_cmd);
+static void target_free_cmd_mem(struct se_cmd *cmd)
+{
+ transport_free_pages(cmd);
+
+ if (cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
+ core_tmr_release_req(cmd->se_tmr_req);
+ if (cmd->t_task_cdb != cmd->__t_task_cdb)
+ kfree(cmd->t_task_cdb);
+}
+
static void target_release_cmd_kref(struct kref *kref)
__releases(&se_cmd->se_sess->sess_cmd_lock)
{
@@ -2523,17 +2517,20 @@ static void target_release_cmd_kref(struct kref *kref)
if (list_empty(&se_cmd->se_cmd_list)) {
spin_unlock(&se_sess->sess_cmd_lock);
+ target_free_cmd_mem(se_cmd);
se_cmd->se_tfo->release_cmd(se_cmd);
return;
}
if (se_sess->sess_tearing_down && se_cmd->cmd_wait_set) {
spin_unlock(&se_sess->sess_cmd_lock);
+ target_free_cmd_mem(se_cmd);
complete(&se_cmd->cmd_wait_comp);
return;
}
list_del(&se_cmd->se_cmd_list);
spin_unlock(&se_sess->sess_cmd_lock);
+ target_free_cmd_mem(se_cmd);
se_cmd->se_tfo->release_cmd(se_cmd);
}
@@ -2545,6 +2542,7 @@ int target_put_sess_cmd(struct se_cmd *se_cmd)
struct se_session *se_sess = se_cmd->se_sess;
if (!se_sess) {
+ target_free_cmd_mem(se_cmd);
se_cmd->se_tfo->release_cmd(se_cmd);
return 1;
}
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index a4bed07..1060c52 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -140,6 +140,7 @@ enum se_cmd_flags_table {
SCF_COMPARE_AND_WRITE = 0x00080000,
SCF_COMPARE_AND_WRITE_POST = 0x00100000,
SCF_PASSTHROUGH_PROT_SG_TO_MEM_NOALLOC = 0x00200000,
+ SCF_ACK_KREF = 0x00400000,
};
/* struct se_dev_entry->lun_flags and struct se_lun->lun_access */
--
1.9.1
--
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