Skip to content

Commit

Permalink
target: Fix LUN_RESET active I/O handling for ACK_KREF
Browse files Browse the repository at this point in the history 
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.

Reviewed-by: Quinn Tran <quinn.tran@qlogic.com>
Cc: Himanshu Madhani <himanshu.madhani@qlogic.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: Mike Christie <mchristi@redhat.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
  • Loading branch information
Nicholas Bellinger committed Feb 3, 2016
1 parent a07100e commit febe562
Show file tree
Hide file tree
Showing 3 changed files with 76 additions and 61 deletions.
69 changes: 46 additions & 23 deletions drivers/target/target_core_tmr.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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(&sess->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,
Expand All @@ -130,34 +158,22 @@ void core_tmr_abort_task(
if (tmr->ref_task_tag != ref_tag)
continue;

if (!kref_get_unless_zero(&se_cmd->cmd_kref))
continue;

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);

target_put_sess_cmd(se_cmd);

goto out;
}
se_cmd->transport_state |= CMD_T_ABORTED;
spin_unlock(&se_cmd->t_state_lock);

list_del_init(&se_cmd->se_cmd_list);
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);
Expand Down Expand Up @@ -242,8 +258,10 @@ 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.
Expand Down Expand Up @@ -282,14 +300,24 @@ 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)
continue;

list_move_tail(&cmd->state_list, &drain_task_list);
cmd->state_active = false;
}
spin_unlock_irqrestore(&dev->execute_task_lock, flags);

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"
Expand All @@ -313,16 +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);
}
}

Expand Down
67 changes: 29 additions & 38 deletions drivers/target/target_core_transport.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -534,9 +534,6 @@ void transport_deregister_session(struct se_session *se_sess)
}
EXPORT_SYMBOL(transport_deregister_session);

/*
* Called with cmd->t_state_lock held.
*/
static void target_remove_from_state_list(struct se_cmd *cmd)
{
struct se_device *dev = cmd->se_dev;
Expand All @@ -561,10 +558,6 @@ 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);

Expand All @@ -574,6 +567,10 @@ 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.
Expand Down Expand Up @@ -627,6 +624,8 @@ 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);
/*
Expand All @@ -638,7 +637,7 @@ 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);
}

Expand Down Expand Up @@ -706,7 +705,7 @@ 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);
Expand Down Expand Up @@ -2222,39 +2221,21 @@ 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.
*/
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;
Expand Down Expand Up @@ -2452,14 +2433,13 @@ static void transport_write_pending_qf(struct se_cmd *cmd)

int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
{
unsigned long flags;
int ret = 0;

if (!(cmd->se_cmd_flags & SCF_SE_LUN_CMD)) {
if (wait_for_tasks && (cmd->se_cmd_flags & SCF_SCSI_TMR_CDB))
transport_wait_for_tasks(cmd);
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);
Expand All @@ -2468,11 +2448,8 @@ int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
* has already added se_cmd to state_list, but fabric has
* failed command before I/O submission.
*/
if (cmd->state_active) {
spin_lock_irqsave(&cmd->t_state_lock, flags);
if (cmd->state_active)
target_remove_from_state_list(cmd);
spin_unlock_irqrestore(&cmd->t_state_lock, flags);
}

if (cmd->se_lun)
transport_lun_remove_cmd(cmd);
Expand Down Expand Up @@ -2517,6 +2494,16 @@ int target_get_sess_cmd(struct se_cmd *se_cmd, bool ack_kref)
}
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)
{
struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
Expand All @@ -2526,17 +2513,20 @@ static void target_release_cmd_kref(struct kref *kref)
spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
if (list_empty(&se_cmd->se_cmd_list)) {
spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
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_irqrestore(&se_sess->sess_cmd_lock, flags);
target_free_cmd_mem(se_cmd);
complete(&se_cmd->cmd_wait_comp);
return;
}
list_del(&se_cmd->se_cmd_list);
spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

target_free_cmd_mem(se_cmd);
se_cmd->se_tfo->release_cmd(se_cmd);
}

Expand All @@ -2548,6 +2538,7 @@ 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;
}
Expand Down
1 change: 1 addition & 0 deletions include/target/target_core_base.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down

0 comments on commit febe562

Please sign in to comment.