b43: Fix possible NULL pointer dereference in DMA code

This fixes a possible NULL pointer dereference in an error path of the
DMA allocation error checking code. This is also necessary for a future
DMA API change that is on its way into the mainline kernel that adds
an additional dev parameter to dma_mapping_error().

This patch moves the whole struct b43_dmaring struct initialization
right before any DMA allocation operation.

Reported-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 32 insertions, 33 deletions

diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
index 6dcbb3c87e7..e23f2f172bd 100644
--- a/drivers/net/wireless/b43/dma.c
+++ b/drivers/net/wireless/b43/dma.c
@@ -795,24 +795,49 @@ struct b43_dmaring *b43_setup_dmaring(struct b43_wldev *dev,
 {
         struct b43_dmaring *ring;
         int err;
-        int nr_slots;
         dma_addr_t dma_test;
 
         ring = kzalloc(sizeof(*ring), GFP_KERNEL);
         if (!ring)
                 goto out;
-        ring->type = type;
 
-        nr_slots = B43_RXRING_SLOTS;
+        ring->nr_slots = B43_RXRING_SLOTS;
         if (for_tx)
-                nr_slots = B43_TXRING_SLOTS;
+                ring->nr_slots = B43_TXRING_SLOTS;
 
-        ring->meta = kcalloc(nr_slots, sizeof(struct b43_dmadesc_meta),
+        ring->meta = kcalloc(ring->nr_slots, sizeof(struct b43_dmadesc_meta),
                              GFP_KERNEL);
         if (!ring->meta)
                 goto err_kfree_ring;
+
+        ring->type = type;
+        ring->dev = dev;
+        ring->mmio_base = b43_dmacontroller_base(type, controller_index);
+        ring->index = controller_index;
+        if (type == B43_DMA_64BIT)
+                ring->ops = &dma64_ops;
+        else
+                ring->ops = &dma32_ops;
         if (for_tx) {
-                ring->txhdr_cache = kcalloc(nr_slots,
+                ring->tx = 1;
+                ring->current_slot = -1;
+        } else {
+                if (ring->index == 0) {
+                        ring->rx_buffersize = B43_DMA0_RX_BUFFERSIZE;
+                        ring->frameoffset = B43_DMA0_RX_FRAMEOFFSET;
+                } else if (ring->index == 3) {
+                        ring->rx_buffersize = B43_DMA3_RX_BUFFERSIZE;
+                        ring->frameoffset = B43_DMA3_RX_FRAMEOFFSET;
+                } else
+                        B43_WARN_ON(1);
+        }
+        spin_lock_init(&ring->lock);
+#ifdef CONFIG_B43_DEBUG
+        ring->last_injected_overflow = jiffies;
+#endif
+
+        if (for_tx) {
+                ring->txhdr_cache = kcalloc(ring->nr_slots,
                                             b43_txhdr_size(dev),
                                             GFP_KERNEL);
                 if (!ring->txhdr_cache)
@@ -828,7 +853,7 @@ struct b43_dmaring *b43_setup_dmaring(struct b43_wldev *dev,
                                           b43_txhdr_size(dev), 1)) {
                         /* ugh realloc */
                         kfree(ring->txhdr_cache);
-                        ring->txhdr_cache = kcalloc(nr_slots,
+                        ring->txhdr_cache = kcalloc(ring->nr_slots,
                                                     b43_txhdr_size(dev),
                                                     GFP_KERNEL | GFP_DMA);
                         if (!ring->txhdr_cache)
@@ -853,32 +878,6 @@ struct b43_dmaring *b43_setup_dmaring(struct b43_wldev *dev,
                                  DMA_TO_DEVICE);
         }
 
-        ring->dev = dev;
-        ring->nr_slots = nr_slots;
-        ring->mmio_base = b43_dmacontroller_base(type, controller_index);
-        ring->index = controller_index;
-        if (type == B43_DMA_64BIT)
-                ring->ops = &dma64_ops;
-        else
-                ring->ops = &dma32_ops;
-        if (for_tx) {
-                ring->tx = 1;
-                ring->current_slot = -1;
-        } else {
-                if (ring->index == 0) {
-                        ring->rx_buffersize = B43_DMA0_RX_BUFFERSIZE;
-                        ring->frameoffset = B43_DMA0_RX_FRAMEOFFSET;
-                } else if (ring->index == 3) {
-                        ring->rx_buffersize = B43_DMA3_RX_BUFFERSIZE;
-                        ring->frameoffset = B43_DMA3_RX_FRAMEOFFSET;
-                } else
-                        B43_WARN_ON(1);
-        }
-        spin_lock_init(&ring->lock);
-#ifdef CONFIG_B43_DEBUG
-        ring->last_injected_overflow = jiffies;
-#endif
-
         err = alloc_ringmemory(ring);
         if (err)
                 goto err_kfree_txhdr_cache;