Staging: ipack/bridges/tpci200: RCU protect slot_irq pointers.

In tpci200_request_irq as well as tpci200_free_irq we set and unset the
pointer to struct slot_irq.  This pointer is accessed in
tpci200_interrupt.  To ensure that the pointer is not freed after it has
been fetched in tpci200_interrupt() it is now protected through RCU.

Signed-off-by: Jens Taprogge <jens.taprogge@taprogge.org>
Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/staging/ipack/bridges/tpci200.c b/drivers/staging/ipack/bridges/tpci200.c
index 24e2a119dd16..9ce577ab9437 100644
--- a/drivers/staging/ipack/bridges/tpci200.c
+++ b/drivers/staging/ipack/bridges/tpci200.c
@@ -132,10 +132,11 @@ static irqreturn_t tpci200_interrupt(int irq, void *dev_id)
 
         if (status_reg & TPCI200_SLOT_INT_MASK) {
                 /* callback to the IRQ handler for the corresponding slot */
+                rcu_read_lock();
                 for (i = 0; i < TPCI200_NB_SLOT; i++) {
                         if (!(status_reg & ((TPCI200_A_INT0 | TPCI200_A_INT1) << (2*i))))
                                 continue;
-                        slot_irq = tpci200->slots[i].irq;
+                        slot_irq = rcu_dereference(tpci200->slots[i].irq);
                         if (slot_irq) {
                                 ret = tpci200_slot_irq(slot_irq);
                         } else {
@@ -147,6 +148,7 @@ static irqreturn_t tpci200_interrupt(int irq, void *dev_id)
                                         TPCI200_INT0_EN | TPCI200_INT1_EN);
                         }
                 }
+                rcu_read_unlock();
         }
 
         return ret;
@@ -303,9 +305,9 @@ static int tpci200_free_irq(struct ipack_device *dev)
 
         __tpci200_free_irq(tpci200, dev);
         slot_irq = tpci200->slots[dev->slot].irq;
-        tpci200->slots[dev->slot].irq = NULL;
+        RCU_INIT_POINTER(tpci200->slots[dev->slot].irq, NULL);
+        synchronize_rcu();
         kfree(slot_irq);
-
         mutex_unlock(&tpci200->mutex);
         return 0;
 }
@@ -490,7 +492,7 @@ static int tpci200_request_irq(struct ipack_device *dev, int vector,
         slot_irq->arg = arg;
         slot_irq->holder = dev;
 
-        tpci200->slots[dev->slot].irq = slot_irq;
+        rcu_assign_pointer(tpci200->slots[dev->slot].irq, slot_irq);
         res = __tpci200_request_irq(tpci200, dev);
 
 out_unlock: