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Subject[PATCH 2/2] mpt2sas: Refcount fw_events and fix unsafe list usage
Date
The fw_event_work struct is concurrently referenced at shutdown, so
add a refcount to protect it, and refactor the code to use it.

Additionally, refactor _scsih_fw_event_cleanup_queue() such that it
no longer iterates over the list without holding the lock, since
_firmware_event_work() concurrently deletes items from the list.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Calvin Owens <calvinowens@fb.com>
---
drivers/scsi/mpt2sas/mpt2sas_scsih.c | 101 ++++++++++++++++++++++++++++-------
1 file changed, 81 insertions(+), 20 deletions(-)

diff --git a/drivers/scsi/mpt2sas/mpt2sas_scsih.c b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
index fad80ce..8b267af 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_scsih.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
@@ -176,9 +176,37 @@ struct fw_event_work {
u8 VP_ID;
u8 ignore;
u16 event;
+ struct kref refcount;
char event_data[0] __aligned(4);
};

+static void fw_event_work_free(struct kref *r)
+{
+ kfree(container_of(r, struct fw_event_work, refcount));
+}
+
+static void fw_event_work_get(struct fw_event_work *fw_work)
+{
+ kref_get(&fw_work->refcount);
+}
+
+static void fw_event_work_put(struct fw_event_work *fw_work)
+{
+ kref_put(&fw_work->refcount, fw_event_work_free);
+}
+
+static struct fw_event_work *alloc_fw_event_work(int len)
+{
+ struct fw_event_work *fw_event;
+
+ fw_event = kzalloc(sizeof(*fw_event) + len, GFP_ATOMIC);
+ if (!fw_event)
+ return NULL;
+
+ kref_init(&fw_event->refcount);
+ return fw_event;
+}
+
/* raid transport support */
static struct raid_template *mpt2sas_raid_template;

@@ -2844,36 +2872,39 @@ _scsih_fw_event_add(struct MPT2SAS_ADAPTER *ioc, struct fw_event_work *fw_event)
return;

spin_lock_irqsave(&ioc->fw_event_lock, flags);
+ fw_event_work_get(fw_event);
list_add_tail(&fw_event->list, &ioc->fw_event_list);
INIT_DELAYED_WORK(&fw_event->delayed_work, _firmware_event_work);
+ fw_event_work_get(fw_event);
queue_delayed_work(ioc->firmware_event_thread,
&fw_event->delayed_work, 0);
spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
}

/**
- * _scsih_fw_event_free - delete fw_event
+ * _scsih_fw_event_del_from_list - delete fw_event from the list
* @ioc: per adapter object
* @fw_event: object describing the event
* Context: This function will acquire ioc->fw_event_lock.
*
- * This removes firmware event object from link list, frees associated memory.
+ * If the fw_event is on the fw_event_list, remove it and do a put.
*
* Return nothing.
*/
static void
-_scsih_fw_event_free(struct MPT2SAS_ADAPTER *ioc, struct fw_event_work
+_scsih_fw_event_del_from_list(struct MPT2SAS_ADAPTER *ioc, struct fw_event_work
*fw_event)
{
unsigned long flags;

spin_lock_irqsave(&ioc->fw_event_lock, flags);
- list_del(&fw_event->list);
- kfree(fw_event);
+ if (!list_empty(&fw_event->list)) {
+ list_del_init(&fw_event->list);
+ fw_event_work_put(fw_event);
+ }
spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
}

-
/**
* _scsih_error_recovery_delete_devices - remove devices not responding
* @ioc: per adapter object
@@ -2888,13 +2919,14 @@ _scsih_error_recovery_delete_devices(struct MPT2SAS_ADAPTER *ioc)
if (ioc->is_driver_loading)
return;

- fw_event = kzalloc(sizeof(struct fw_event_work), GFP_ATOMIC);
+ fw_event = alloc_fw_event_work(0);
if (!fw_event)
return;

fw_event->event = MPT2SAS_REMOVE_UNRESPONDING_DEVICES;
fw_event->ioc = ioc;
_scsih_fw_event_add(ioc, fw_event);
+ fw_event_work_put(fw_event);
}

/**
@@ -2908,12 +2940,29 @@ mpt2sas_port_enable_complete(struct MPT2SAS_ADAPTER *ioc)
{
struct fw_event_work *fw_event;

- fw_event = kzalloc(sizeof(struct fw_event_work), GFP_ATOMIC);
+ fw_event = alloc_fw_event_work(0);
if (!fw_event)
return;
fw_event->event = MPT2SAS_PORT_ENABLE_COMPLETE;
fw_event->ioc = ioc;
_scsih_fw_event_add(ioc, fw_event);
+ fw_event_work_put(fw_event);
+}
+
+static struct fw_event_work *dequeue_next_fw_event(struct MPT2SAS_ADAPTER *ioc)
+{
+ unsigned long flags;
+ struct fw_event_work *fw_event = NULL;
+
+ spin_lock_irqsave(&ioc->fw_event_lock, flags);
+ if (!list_empty(&ioc->fw_event_list)) {
+ fw_event = list_first_entry(&ioc->fw_event_list,
+ struct fw_event_work, list);
+ list_del_init(&fw_event->list);
+ }
+ spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
+
+ return fw_event;
}

/**
@@ -2928,17 +2977,25 @@ mpt2sas_port_enable_complete(struct MPT2SAS_ADAPTER *ioc)
static void
_scsih_fw_event_cleanup_queue(struct MPT2SAS_ADAPTER *ioc)
{
- struct fw_event_work *fw_event, *next;
+ struct fw_event_work *fw_event;

if (list_empty(&ioc->fw_event_list) ||
!ioc->firmware_event_thread || in_interrupt())
return;

- list_for_each_entry_safe(fw_event, next, &ioc->fw_event_list, list) {
- if (cancel_delayed_work_sync(&fw_event->delayed_work)) {
- _scsih_fw_event_free(ioc, fw_event);
- continue;
- }
+ while ((fw_event = dequeue_next_fw_event(ioc))) {
+ /*
+ * Wait on the fw_event to complete. If this returns 1, then
+ * the event was never executed, and we need a put for the
+ * reference the delayed_work had on the fw_event.
+ *
+ * If it did execute, we wait for it to finish, and the put will
+ * happen from _firmware_event_work()
+ */
+ if (cancel_delayed_work_sync(&fw_event->delayed_work))
+ fw_event_work_put(fw_event);
+
+ fw_event_work_put(fw_event);
}
}

@@ -4419,13 +4476,14 @@ _scsih_send_event_to_turn_on_pfa_led(struct MPT2SAS_ADAPTER *ioc, u16 handle)
{
struct fw_event_work *fw_event;

- fw_event = kzalloc(sizeof(struct fw_event_work), GFP_ATOMIC);
+ fw_event = alloc_fw_event_work(0);
if (!fw_event)
return;
fw_event->event = MPT2SAS_TURN_ON_PFA_LED;
fw_event->device_handle = handle;
fw_event->ioc = ioc;
_scsih_fw_event_add(ioc, fw_event);
+ fw_event_work_put(fw_event);
}

/**
@@ -7523,10 +7581,11 @@ _firmware_event_work(struct work_struct *work)
struct fw_event_work, delayed_work.work);
struct MPT2SAS_ADAPTER *ioc = fw_event->ioc;

+ _scsih_fw_event_del_from_list(ioc, fw_event);
+
/* the queue is being flushed so ignore this event */
- if (ioc->remove_host ||
- ioc->pci_error_recovery) {
- _scsih_fw_event_free(ioc, fw_event);
+ if (ioc->remove_host || ioc->pci_error_recovery) {
+ fw_event_work_put(fw_event);
return;
}

@@ -7582,7 +7641,8 @@ _firmware_event_work(struct work_struct *work)
_scsih_sas_ir_operation_status_event(ioc, fw_event);
break;
}
- _scsih_fw_event_free(ioc, fw_event);
+
+ fw_event_work_put(fw_event);
}

/**
@@ -7720,7 +7780,7 @@ mpt2sas_scsih_event_callback(struct MPT2SAS_ADAPTER *ioc, u8 msix_index,
}

sz = le16_to_cpu(mpi_reply->EventDataLength) * 4;
- fw_event = kzalloc(sizeof(*fw_event) + sz, GFP_ATOMIC);
+ fw_event = alloc_fw_event_work(sz);
if (!fw_event) {
printk(MPT2SAS_ERR_FMT "failure at %s:%d/%s()!\n",
ioc->name, __FILE__, __LINE__, __func__);
@@ -7733,6 +7793,7 @@ mpt2sas_scsih_event_callback(struct MPT2SAS_ADAPTER *ioc, u8 msix_index,
fw_event->VP_ID = mpi_reply->VP_ID;
fw_event->event = event;
_scsih_fw_event_add(ioc, fw_event);
+ fw_event_work_put(fw_event);
return;
}

--
1.8.1


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