[PATCH AUTOSEL 5.15 05/22] scsi: ibmvfc: Remove BUG_ON in the case of an empty event pool

Sasha Levin
2023-11-07T16:01:15Z

From: Tyrel Datwyler <tyreld@linux.ibm.com>

[ Upstream commit b39f2d10b86d0af353ea339e5815820026bca48f ]

In practice the driver should never send more commands than are allocated
to a queue's event pool. In the unlikely event that this happens, the code
asserts a BUG_ON, and in the case that the kernel is not configured to
crash on panic returns a junk event pointer from the empty event list
causing things to spiral from there. This BUG_ON is a historical artifact
of the ibmvfc driver first being upstreamed, and it is well known now that
the use of BUG_ON is bad practice except in the most unrecoverable
scenario. There is nothing about this scenario that prevents the driver
from recovering and carrying on.

Remove the BUG_ON in question from ibmvfc_get_event() and return a NULL
pointer in the case of an empty event pool. Update all call sites to
ibmvfc_get_event() to check for a NULL pointer and perfrom the appropriate
failure or recovery action.

Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Link: https://lore.kernel.org/r/20230921225435.3537728-2-tyreld@linux.ibm.com
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/ibmvscsi/ibmvfc.c | 124 ++++++++++++++++++++++++++++++++-
1 file changed, 122 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
index 45ef78f388dc9..e1895686987f0 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc.c
@@ -1519,7 +1519,11 @@ static struct ibmvfc_event *ibmvfc_get_event(struct ibmvfc_queue *queue)
unsigned long flags;

spin_lock_irqsave(&queue->l_lock, flags);
- BUG_ON(list_empty(&queue->free));
+ if (list_empty(&queue->free)) {
+ ibmvfc_log(queue->vhost, 4, "empty event pool on queue:%ld\n", queue->hwq_id);
+ spin_unlock_irqrestore(&queue->l_lock, flags);
+ return NULL;
+ }
evt = list_entry(queue->free.next, struct ibmvfc_event, queue_list);
atomic_set(&evt->free, 0);
list_del(&evt->queue_list);
@@ -1948,9 +1952,15 @@ static int ibmvfc_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *cmnd)
if (vhost->using_channels) {
scsi_channel = hwq % vhost->scsi_scrqs.active_queues;
evt = ibmvfc_get_event(&vhost->scsi_scrqs.scrqs[scsi_channel]);
+ if (!evt)
+ return SCSI_MLQUEUE_HOST_BUSY;
+
evt->hwq = hwq % vhost->scsi_scrqs.active_queues;
- } else
+ } else {
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt)
+ return SCSI_MLQUEUE_HOST_BUSY;
+ }

ibmvfc_init_event(evt, ibmvfc_scsi_done, IBMVFC_CMD_FORMAT);
evt->cmnd = cmnd;
@@ -2038,6 +2048,11 @@ static int ibmvfc_bsg_timeout(struct bsg_job *job)

vhost->aborting_passthru = 1;
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ spin_unlock_irqrestore(vhost->host->host_lock, flags);
+ return -ENOMEM;
+ }
+
ibmvfc_init_event(evt, ibmvfc_bsg_timeout_done, IBMVFC_MAD_FORMAT);

tmf = &evt->iu.tmf;
@@ -2096,6 +2111,10 @@ static int ibmvfc_bsg_plogi(struct ibmvfc_host *vhost, unsigned int port_id)
goto unlock_out;

evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ rc = -ENOMEM;
+ goto unlock_out;
+ }
ibmvfc_init_event(evt, ibmvfc_sync_completion, IBMVFC_MAD_FORMAT);
plogi = &evt->iu.plogi;
memset(plogi, 0, sizeof(*plogi));
@@ -2214,6 +2233,11 @@ static int ibmvfc_bsg_request(struct bsg_job *job)
}

evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ spin_unlock_irqrestore(vhost->host->host_lock, flags);
+ rc = -ENOMEM;
+ goto out;
+ }
ibmvfc_init_event(evt, ibmvfc_sync_completion, IBMVFC_MAD_FORMAT);
mad = &evt->iu.passthru;

@@ -2302,6 +2326,11 @@ static int ibmvfc_reset_device(struct scsi_device *sdev, int type, char *desc)
else
evt = ibmvfc_get_event(&vhost->crq);

+ if (!evt) {
+ spin_unlock_irqrestore(vhost->host->host_lock, flags);
+ return -ENOMEM;
+ }
+
ibmvfc_init_event(evt, ibmvfc_sync_completion, IBMVFC_CMD_FORMAT);
tmf = ibmvfc_init_vfc_cmd(evt, sdev);
iu = ibmvfc_get_fcp_iu(vhost, tmf);
@@ -2505,6 +2534,8 @@ static struct ibmvfc_event *ibmvfc_init_tmf(struct ibmvfc_queue *queue,
struct ibmvfc_tmf *tmf;

evt = ibmvfc_get_event(queue);
+ if (!evt)
+ return NULL;
ibmvfc_init_event(evt, ibmvfc_sync_completion, IBMVFC_MAD_FORMAT);

tmf = &evt->iu.tmf;
@@ -2561,6 +2592,11 @@ static int ibmvfc_cancel_all_mq(struct scsi_device *sdev, int type)

if (found_evt && vhost->logged_in) {
evt = ibmvfc_init_tmf(&queues[i], sdev, type);
+ if (!evt) {
+ spin_unlock(queues[i].q_lock);
+ spin_unlock_irqrestore(vhost->host->host_lock, flags);
+ return -ENOMEM;
+ }
evt->sync_iu = &queues[i].cancel_rsp;
ibmvfc_send_event(evt, vhost, default_timeout);
list_add_tail(&evt->cancel, &cancelq);
@@ -2774,6 +2810,10 @@ static int ibmvfc_abort_task_set(struct scsi_device *sdev)

if (vhost->state == IBMVFC_ACTIVE) {
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ spin_unlock_irqrestore(vhost->host->host_lock, flags);
+ return -ENOMEM;
+ }
ibmvfc_init_event(evt, ibmvfc_sync_completion, IBMVFC_CMD_FORMAT);
tmf = ibmvfc_init_vfc_cmd(evt, sdev);
iu = ibmvfc_get_fcp_iu(vhost, tmf);
@@ -4030,6 +4070,12 @@ static void ibmvfc_tgt_send_prli(struct ibmvfc_target *tgt)

kref_get(&tgt->kref);
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_NONE);
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ return;
+ }
vhost->discovery_threads++;
ibmvfc_init_event(evt, ibmvfc_tgt_prli_done, IBMVFC_MAD_FORMAT);
evt->tgt = tgt;
@@ -4137,6 +4183,12 @@ static void ibmvfc_tgt_send_plogi(struct ibmvfc_target *tgt)
kref_get(&tgt->kref);
tgt->logo_rcvd = 0;
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_NONE);
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ return;
+ }
vhost->discovery_threads++;
ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_INIT_WAIT);
ibmvfc_init_event(evt, ibmvfc_tgt_plogi_done, IBMVFC_MAD_FORMAT);
@@ -4213,6 +4265,8 @@ static struct ibmvfc_event *__ibmvfc_tgt_get_implicit_logout_evt(struct ibmvfc_t

kref_get(&tgt->kref);
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt)
+ return NULL;
ibmvfc_init_event(evt, done, IBMVFC_MAD_FORMAT);
evt->tgt = tgt;
mad = &evt->iu.implicit_logout;
@@ -4240,6 +4294,13 @@ static void ibmvfc_tgt_implicit_logout(struct ibmvfc_target *tgt)
vhost->discovery_threads++;
evt = __ibmvfc_tgt_get_implicit_logout_evt(tgt,
ibmvfc_tgt_implicit_logout_done);
+ if (!evt) {
+ vhost->discovery_threads--;
+ ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_NONE);
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ return;
+ }

ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_INIT_WAIT);
if (ibmvfc_send_event(evt, vhost, default_timeout)) {
@@ -4379,6 +4440,12 @@ static void ibmvfc_tgt_move_login(struct ibmvfc_target *tgt)

kref_get(&tgt->kref);
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_DEL_RPORT);
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ return;
+ }
vhost->discovery_threads++;
ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_INIT_WAIT);
ibmvfc_init_event(evt, ibmvfc_tgt_move_login_done, IBMVFC_MAD_FORMAT);
@@ -4545,6 +4612,14 @@ static void ibmvfc_adisc_timeout(struct timer_list *t)
vhost->abort_threads++;
kref_get(&tgt->kref);
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ tgt_err(tgt, "Failed to get cancel event for ADISC.\n");
+ vhost->abort_threads--;
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ spin_unlock_irqrestore(vhost->host->host_lock, flags);
+ return;
+ }
ibmvfc_init_event(evt, ibmvfc_tgt_adisc_cancel_done, IBMVFC_MAD_FORMAT);

evt->tgt = tgt;
@@ -4595,6 +4670,12 @@ static void ibmvfc_tgt_adisc(struct ibmvfc_target *tgt)

kref_get(&tgt->kref);
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_NONE);
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ return;
+ }
vhost->discovery_threads++;
ibmvfc_init_event(evt, ibmvfc_tgt_adisc_done, IBMVFC_MAD_FORMAT);
evt->tgt = tgt;
@@ -4698,6 +4779,12 @@ static void ibmvfc_tgt_query_target(struct ibmvfc_target *tgt)

kref_get(&tgt->kref);
evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ ibmvfc_set_tgt_action(tgt, IBMVFC_TGT_ACTION_NONE);
+ kref_put(&tgt->kref, ibmvfc_release_tgt);
+ __ibmvfc_reset_host(vhost);
+ return;
+ }
vhost->discovery_threads++;
evt->tgt = tgt;
ibmvfc_init_event(evt, ibmvfc_tgt_query_target_done, IBMVFC_MAD_FORMAT);
@@ -4870,6 +4957,13 @@ static void ibmvfc_discover_targets(struct ibmvfc_host *vhost)
{
struct ibmvfc_discover_targets *mad;
struct ibmvfc_event *evt = ibmvfc_get_event(&vhost->crq);
+ int level = IBMVFC_DEFAULT_LOG_LEVEL;
+
+ if (!evt) {
+ ibmvfc_log(vhost, level, "Discover Targets failed: no available events\n");
+ ibmvfc_hard_reset_host(vhost);
+ return;
+ }

ibmvfc_init_event(evt, ibmvfc_discover_targets_done, IBMVFC_MAD_FORMAT);
mad = &evt->iu.discover_targets;
@@ -4947,8 +5041,15 @@ static void ibmvfc_channel_setup(struct ibmvfc_host *vhost)
struct ibmvfc_scsi_channels *scrqs = &vhost->scsi_scrqs;
unsigned int num_channels =
min(vhost->client_scsi_channels, vhost->max_vios_scsi_channels);
+ int level = IBMVFC_DEFAULT_LOG_LEVEL;
int i;

+ if (!evt) {
+ ibmvfc_log(vhost, level, "Channel Setup failed: no available events\n");
+ ibmvfc_hard_reset_host(vhost);
+ return;
+ }
+
memset(setup_buf, 0, sizeof(*setup_buf));
if (num_channels == 0)
setup_buf->flags = cpu_to_be32(IBMVFC_CANCEL_CHANNELS);
@@ -5010,6 +5111,13 @@ static void ibmvfc_channel_enquiry(struct ibmvfc_host *vhost)
{
struct ibmvfc_channel_enquiry *mad;
struct ibmvfc_event *evt = ibmvfc_get_event(&vhost->crq);
+ int level = IBMVFC_DEFAULT_LOG_LEVEL;
+
+ if (!evt) {
+ ibmvfc_log(vhost, level, "Channel Enquiry failed: no available events\n");
+ ibmvfc_hard_reset_host(vhost);
+ return;
+ }

ibmvfc_init_event(evt, ibmvfc_channel_enquiry_done, IBMVFC_MAD_FORMAT);
mad = &evt->iu.channel_enquiry;
@@ -5132,6 +5240,12 @@ static void ibmvfc_npiv_login(struct ibmvfc_host *vhost)
struct ibmvfc_npiv_login_mad *mad;
struct ibmvfc_event *evt = ibmvfc_get_event(&vhost->crq);

+ if (!evt) {
+ ibmvfc_dbg(vhost, "NPIV Login failed: no available events\n");
+ ibmvfc_hard_reset_host(vhost);
+ return;
+ }
+
ibmvfc_gather_partition_info(vhost);
ibmvfc_set_login_info(vhost);
ibmvfc_init_event(evt, ibmvfc_npiv_login_done, IBMVFC_MAD_FORMAT);
@@ -5196,6 +5310,12 @@ static void ibmvfc_npiv_logout(struct ibmvfc_host *vhost)
struct ibmvfc_event *evt;

evt = ibmvfc_get_event(&vhost->crq);
+ if (!evt) {
+ ibmvfc_dbg(vhost, "NPIV Logout failed: no available events\n");
+ ibmvfc_hard_reset_host(vhost);
+ return;
+ }
+
ibmvfc_init_event(evt, ibmvfc_npiv_logout_done, IBMVFC_MAD_FORMAT);

mad = &evt->iu.npiv_logout;
--
2.42.0