[PATCH -next] mtip32xx: fix potential NULL pointer dereference in mtip_timeout_function()

[PATCH -next] mtip32xx: fix potential NULL pointer dereference in mtip_timeout_function()

[Wei Yongjun]

From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>

The dereference to port should be moved below the NULL test.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
---
 drivers/block/mtip32xx/mtip32xx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index adc6f36..fe16b32 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -559,7 +559,7 @@ static void mtip_timeout_function(unsigned long int data)
 	struct mtip_cmd *command;
 	int tag, cmdto_cnt = 0;
 	unsigned int bit, group;
-	unsigned int num_command_slots = port->dd->slot_groups * 32;
+	unsigned int num_command_slots;
 	unsigned long to, tagaccum[SLOTBITS_IN_LONGS];
 
 	if (unlikely(!port))
@@ -572,6 +572,7 @@ static void mtip_timeout_function(unsigned long int data)
 	}
 	/* clear the tag accumulator */
 	memset(tagaccum, 0, SLOTBITS_IN_LONGS * sizeof(long));
+	num_command_slots = port->dd->slot_groups * 32;
 
 	for (tag = 0; tag < num_command_slots; tag++) {
 		/*

Re: [PATCH -next] mtip32xx: fix potential NULL pointer dereference in mtip_timeout_function()

[Jens Axboe]

On 2012-11-08 10:35, Wei Yongjun wrote:
> From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
> 
> The dereference to port should be moved below the NULL test.
> 
> dpatch engine is used to auto generate this patch.
> (https://github.com/weiyj/dpatch)

Thanks, it definitely doesn't make sense to check for !port after having
dereferenced it. Applied.

-- 
Jens Axboe