[PATCH V2 1/1] ARM: dmabounce: fix dmabounce may cause crash issue

[b29396@freescale.com (Aisheng.Dong)]

The map_single does not check if dev is NULL which may cause kernel panic
like follows:
Unable to handle kernel NULL pointer dereference at virtual address 000000bc
pgd = 80004000
[000000bc] *pgd=00000000
Internal error: Oops: 5 [#1] PREEMPT
last sysfs file:
Modules linked in:
CPU: 0    Not tainted  (2.6.35.3-00845-g204c152-dirty #112)
PC is at dma_map_single+0x2c/0x2a0
LR is at fec_enet_interrupt+0x1d4/0x450
pc : [<8003cf04>]    lr : [<802936b8>]    psr: 60000193
sp : 80809ec8  ip : 00000080  fp : 99308040
r10: 99308040  r9 : 00000002  r8 : 99074f00
r7 : fa0a5000  r6 : 00000000  r5 : 00000060  r4 : 992e4000
r3 : 00000002  r2 : 8080cac0  r1 : 99308040  r0 : 00000000

The patch checks the dev to avoid this issue and align with the
original dma_map_single to allow dev is NULL.

Signed-off-by: Aisheng.Dong <b29396@freescale.com>
Signed-off-by: Jason.Liu <r64343@freescale.com>

---
Changes for v2:
 Address the comments from Mikael:
 -Fix device_info may be used uninitialized.
---
 arch/arm/common/dmabounce.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm/common/dmabounce.c b/arch/arm/common/dmabounce.c
index e568163..789e84a 100644
--- a/arch/arm/common/dmabounce.c
+++ b/arch/arm/common/dmabounce.c
@@ -222,16 +222,19 @@ static struct safe_buffer *find_safe_buffer_dev(struct device *dev,
 static inline dma_addr_t map_single(struct device *dev, void *ptr, size_t size,
 		enum dma_data_direction dir)
 {
-	struct dmabounce_device_info *device_info = dev->archdata.dmabounce;
+	struct dmabounce_device_info *device_info = NULL;
 	dma_addr_t dma_addr;
 	int needs_bounce = 0;
 
+	if (dev)
+		device_info = dev->archdata.dmabounce;
+
 	if (device_info)
 		DO_STATS ( device_info->map_op_count++ );
 
 	dma_addr = virt_to_dma(dev, ptr);
 
-	if (dev->dma_mask) {
+	if (dev && dev->dma_mask) {
 		unsigned long mask = *dev->dma_mask;
 		unsigned long limit;
 
-- 
1.7.0.4