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scsi: target: tcmu: Userspace must not complete queued commands
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When tcmu queues a new command - no matter whether in command ring or in
qfull_queue - a cmd_id from IDR udev->commands is assigned to the command.

If userspace sends a wrong command completion containing the cmd_id of a
command on the qfull_queue, tcmu_handle_completions() finds the command in
the IDR and calls tcmu_handle_completion() for it. This might do some nasty
things because commands in qfull_queue do not have a valid dbi list.

To fix this bug, we no longer add queued commands to the idr.  Instead the
cmd_id is assign when a command is written to the command ring.

Due to this change I had to adapt the source code at several places where
up to now an idr_for_each had been done.

[mkp: fix checkpatch warnings]

Link: https://lore.kernel.org/r/20200518164833.12775-1-bstroesser@ts.fujitsu.com
Acked-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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Bodo Stroesser authored and Martin K. Petersen committed May 20, 2020
1 parent 5482d56 commit 61fb248
Showing 1 changed file with 71 additions and 83 deletions.
154 changes: 71 additions & 83 deletions drivers/target/target_core_user.c
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Original file line number Diff line number Diff line change
Expand Up @@ -882,41 +882,24 @@ static inline size_t tcmu_cmd_get_cmd_size(struct tcmu_cmd *tcmu_cmd,
return command_size;
}

static int tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd, unsigned int tmo,
struct timer_list *timer)
static void tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd, unsigned int tmo,
struct timer_list *timer)
{
struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
int cmd_id;

if (tcmu_cmd->cmd_id)
goto setup_timer;

cmd_id = idr_alloc(&udev->commands, tcmu_cmd, 1, USHRT_MAX, GFP_NOWAIT);
if (cmd_id < 0) {
pr_err("tcmu: Could not allocate cmd id.\n");
return cmd_id;
}
tcmu_cmd->cmd_id = cmd_id;

pr_debug("allocated cmd %u for dev %s tmo %lu\n", tcmu_cmd->cmd_id,
udev->name, tmo / MSEC_PER_SEC);

setup_timer:
if (!tmo)
return 0;
return;

tcmu_cmd->deadline = round_jiffies_up(jiffies + msecs_to_jiffies(tmo));
if (!timer_pending(timer))
mod_timer(timer, tcmu_cmd->deadline);

return 0;
pr_debug("Timeout set up for cmd %p, dev = %s, tmo = %lu\n", tcmu_cmd,
tcmu_cmd->tcmu_dev->name, tmo / MSEC_PER_SEC);
}

static int add_to_qfull_queue(struct tcmu_cmd *tcmu_cmd)
{
struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
unsigned int tmo;
int ret;

/*
* For backwards compat if qfull_time_out is not set use
Expand All @@ -931,13 +914,11 @@ static int add_to_qfull_queue(struct tcmu_cmd *tcmu_cmd)
else
tmo = TCMU_TIME_OUT;

ret = tcmu_setup_cmd_timer(tcmu_cmd, tmo, &udev->qfull_timer);
if (ret)
return ret;
tcmu_setup_cmd_timer(tcmu_cmd, tmo, &udev->qfull_timer);

list_add_tail(&tcmu_cmd->queue_entry, &udev->qfull_queue);
pr_debug("adding cmd %u on dev %s to ring space wait queue\n",
tcmu_cmd->cmd_id, udev->name);
pr_debug("adding cmd %p on dev %s to ring space wait queue\n",
tcmu_cmd, udev->name);
return 0;
}

Expand All @@ -959,7 +940,7 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err)
struct tcmu_mailbox *mb;
struct tcmu_cmd_entry *entry;
struct iovec *iov;
int iov_cnt, ret;
int iov_cnt, cmd_id;
uint32_t cmd_head;
uint64_t cdb_off;
bool copy_to_data_area;
Expand Down Expand Up @@ -1060,14 +1041,21 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err)
}
entry->req.iov_bidi_cnt = iov_cnt;

ret = tcmu_setup_cmd_timer(tcmu_cmd, udev->cmd_time_out,
&udev->cmd_timer);
if (ret) {
tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
cmd_id = idr_alloc(&udev->commands, tcmu_cmd, 1, USHRT_MAX, GFP_NOWAIT);
if (cmd_id < 0) {
pr_err("tcmu: Could not allocate cmd id.\n");

tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
*scsi_err = TCM_OUT_OF_RESOURCES;
return -1;
}
tcmu_cmd->cmd_id = cmd_id;

pr_debug("allocated cmd id %u for cmd %p dev %s\n", tcmu_cmd->cmd_id,
tcmu_cmd, udev->name);

tcmu_setup_cmd_timer(tcmu_cmd, udev->cmd_time_out, &udev->cmd_timer);

entry->hdr.cmd_id = tcmu_cmd->cmd_id;

/*
Expand Down Expand Up @@ -1279,50 +1267,39 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
return handled;
}

static int tcmu_check_expired_cmd(int id, void *p, void *data)
static void tcmu_check_expired_ring_cmd(struct tcmu_cmd *cmd)
{
struct tcmu_cmd *cmd = p;
struct tcmu_dev *udev = cmd->tcmu_dev;
u8 scsi_status;
struct se_cmd *se_cmd;
bool is_running;

if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
return 0;

if (!time_after(jiffies, cmd->deadline))
return 0;
return;

is_running = test_bit(TCMU_CMD_BIT_INFLIGHT, &cmd->flags);
set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
list_del_init(&cmd->queue_entry);
se_cmd = cmd->se_cmd;
cmd->se_cmd = NULL;

if (is_running) {
/*
* If cmd_time_out is disabled but qfull is set deadline
* will only reflect the qfull timeout. Ignore it.
*/
if (!udev->cmd_time_out)
return 0;
pr_debug("Timing out inflight cmd %u on dev %s.\n",
cmd->cmd_id, cmd->tcmu_dev->name);

set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
/*
* target_complete_cmd will translate this to LUN COMM FAILURE
*/
scsi_status = SAM_STAT_CHECK_CONDITION;
list_del_init(&cmd->queue_entry);
cmd->se_cmd = NULL;
} else {
list_del_init(&cmd->queue_entry);
idr_remove(&udev->commands, id);
tcmu_free_cmd(cmd);
scsi_status = SAM_STAT_TASK_SET_FULL;
}
target_complete_cmd(se_cmd, SAM_STAT_CHECK_CONDITION);
}

pr_debug("Timing out cmd %u on dev %s that is %s.\n",
id, udev->name, is_running ? "inflight" : "queued");
static void tcmu_check_expired_queue_cmd(struct tcmu_cmd *cmd)
{
struct se_cmd *se_cmd;

target_complete_cmd(se_cmd, scsi_status);
return 0;
if (!time_after(jiffies, cmd->deadline))
return;

list_del_init(&cmd->queue_entry);
se_cmd = cmd->se_cmd;
tcmu_free_cmd(cmd);

pr_debug("Timing out queued cmd %p on dev %s.\n",
cmd, cmd->tcmu_dev->name);

target_complete_cmd(se_cmd, SAM_STAT_TASK_SET_FULL);
}

static void tcmu_device_timedout(struct tcmu_dev *udev)
Expand Down Expand Up @@ -1407,16 +1384,15 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
return &udev->se_dev;
}

static bool run_qfull_queue(struct tcmu_dev *udev, bool fail)
static void run_qfull_queue(struct tcmu_dev *udev, bool fail)
{
struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
LIST_HEAD(cmds);
bool drained = true;
sense_reason_t scsi_ret;
int ret;

if (list_empty(&udev->qfull_queue))
return true;
return;

pr_debug("running %s's cmdr queue forcefail %d\n", udev->name, fail);

Expand All @@ -1425,11 +1401,10 @@ static bool run_qfull_queue(struct tcmu_dev *udev, bool fail)
list_for_each_entry_safe(tcmu_cmd, tmp_cmd, &cmds, queue_entry) {
list_del_init(&tcmu_cmd->queue_entry);

pr_debug("removing cmd %u on dev %s from queue\n",
tcmu_cmd->cmd_id, udev->name);
pr_debug("removing cmd %p on dev %s from queue\n",
tcmu_cmd, udev->name);

if (fail) {
idr_remove(&udev->commands, tcmu_cmd->cmd_id);
/*
* We were not able to even start the command, so
* fail with busy to allow a retry in case runner
Expand All @@ -1444,10 +1419,8 @@ static bool run_qfull_queue(struct tcmu_dev *udev, bool fail)

ret = queue_cmd_ring(tcmu_cmd, &scsi_ret);
if (ret < 0) {
pr_debug("cmd %u on dev %s failed with %u\n",
tcmu_cmd->cmd_id, udev->name, scsi_ret);

idr_remove(&udev->commands, tcmu_cmd->cmd_id);
pr_debug("cmd %p on dev %s failed with %u\n",
tcmu_cmd, udev->name, scsi_ret);
/*
* Ignore scsi_ret for now. target_complete_cmd
* drops it.
Expand All @@ -1462,13 +1435,11 @@ static bool run_qfull_queue(struct tcmu_dev *udev, bool fail)
* the queue
*/
list_splice_tail(&cmds, &udev->qfull_queue);
drained = false;
break;
}
}

tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);
return drained;
}

static int tcmu_irqcontrol(struct uio_info *info, s32 irq_on)
Expand Down Expand Up @@ -1652,6 +1623,8 @@ static void tcmu_dev_kref_release(struct kref *kref)
if (tcmu_check_and_free_pending_cmd(cmd) != 0)
all_expired = false;
}
if (!list_empty(&udev->qfull_queue))
all_expired = false;
idr_destroy(&udev->commands);
WARN_ON(!all_expired);

Expand Down Expand Up @@ -2037,9 +2010,6 @@ static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
mutex_lock(&udev->cmdr_lock);

idr_for_each_entry(&udev->commands, cmd, i) {
if (!test_bit(TCMU_CMD_BIT_INFLIGHT, &cmd->flags))
continue;

pr_debug("removing cmd %u on dev %s from ring (is expired %d)\n",
cmd->cmd_id, udev->name,
test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags));
Expand Down Expand Up @@ -2076,6 +2046,8 @@ static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)

del_timer(&udev->cmd_timer);

run_qfull_queue(udev, false);

mutex_unlock(&udev->cmdr_lock);
}

Expand Down Expand Up @@ -2699,6 +2671,7 @@ static void find_free_blocks(void)
static void check_timedout_devices(void)
{
struct tcmu_dev *udev, *tmp_dev;
struct tcmu_cmd *cmd, *tmp_cmd;
LIST_HEAD(devs);

spin_lock_bh(&timed_out_udevs_lock);
Expand All @@ -2709,9 +2682,24 @@ static void check_timedout_devices(void)
spin_unlock_bh(&timed_out_udevs_lock);

mutex_lock(&udev->cmdr_lock);
idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);

tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
/*
* If cmd_time_out is disabled but qfull is set deadline
* will only reflect the qfull timeout. Ignore it.
*/
if (udev->cmd_time_out) {
list_for_each_entry_safe(cmd, tmp_cmd,
&udev->inflight_queue,
queue_entry) {
tcmu_check_expired_ring_cmd(cmd);
}
tcmu_set_next_deadline(&udev->inflight_queue,
&udev->cmd_timer);
}
list_for_each_entry_safe(cmd, tmp_cmd, &udev->qfull_queue,
queue_entry) {
tcmu_check_expired_queue_cmd(cmd);
}
tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);

mutex_unlock(&udev->cmdr_lock);
Expand Down

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