[PATCH] drivers:block:mtip32xx:mtip32xx:change the order of null-pointer dereference validation

[PATCH] drivers:block:mtip32xx:mtip32xx:change the order of null-pointer dereference validation

[Heloise]

Signed-off-by: Heloise <os@iscas.ac.cn>

mtip_async_complete() uses the variable port 'port->dd'at the begining, then
validates null-pointer dereference of port 'unlikely(!port)'. Change the order
of validation.
---
 drivers/block/mtip32xx/mtip32xx.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 1d1dc11..feed61a 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -228,10 +228,13 @@ static struct mtip_cmd *mtip_cmd_from_tag(struct driver_data *dd,
 static void mtip_async_complete(struct mtip_port *port,
 				int tag, struct mtip_cmd *cmd, int status)
 {
+	if (unlikely(!port))
+		return;
+
 	struct driver_data *dd = port->dd;
 	struct request *rq;
 
-	if (unlikely(!dd) || unlikely(!port))
+	if (unlikely(!dd))
 		return;
 
 	if (unlikely(status == PORT_IRQ_TF_ERR)) {
-- 
2.1.0

Re: [PATCH] drivers:block:mtip32xx:mtip32xx:change the order of null-pointer dereference validation

[Jens Axboe]

On 04/25/2017 06:30 PM, Heloise wrote:
> Signed-off-by: Heloise <os@iscas.ac.cn>
> 
> mtip_async_complete() uses the variable port 'port->dd'at the begining, then
> validates null-pointer dereference of port 'unlikely(!port)'. Change the order
> of validation.
> ---
>  drivers/block/mtip32xx/mtip32xx.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
> index 1d1dc11..feed61a 100644
> --- a/drivers/block/mtip32xx/mtip32xx.c
> +++ b/drivers/block/mtip32xx/mtip32xx.c
> @@ -228,10 +228,13 @@ static struct mtip_cmd *mtip_cmd_from_tag(struct driver_data *dd,
>  static void mtip_async_complete(struct mtip_port *port,
>  				int tag, struct mtip_cmd *cmd, int status)
>  {
> +	if (unlikely(!port))
> +		return;
> +
>  	struct driver_data *dd = port->dd;
>  	struct request *rq;
>  
> -	if (unlikely(!dd) || unlikely(!port))
> +	if (unlikely(!dd))
>  		return;

Doesn't matter, since 'dd' isn't dereferenced before checking if
'port' is NULL.

-- 
Jens Axboe

Re: [PATCH] drivers:block:mtip32xx:mtip32xx:change the order of null-pointer dereference validation

[kbuild test robot]

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Hi Heloise,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.11-rc8 next-20170426]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Heloise/drivers-block-mtip32xx-mtip32xx-change-the-order-of-null-pointer-dereference-validation/20170426-235410
config: x86_64-acpi-redef (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   drivers/block/mtip32xx/mtip32xx.c: In function 'mtip_async_complete':
>> drivers/block/mtip32xx/mtip32xx.c:234:2: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
     struct driver_data *dd = port->dd;
     ^~~~~~

vim +234 drivers/block/mtip32xx/mtip32xx.c

8f8b8995 Asai Thambi S P 2013-09-11  218   * clears the allocated bit associated with the completed command.
8f8b8995 Asai Thambi S P 2013-09-11  219   *
8f8b8995 Asai Thambi S P 2013-09-11  220   * @port   Pointer to the port data structure.
8f8b8995 Asai Thambi S P 2013-09-11  221   * @tag    Tag of the command.
8f8b8995 Asai Thambi S P 2013-09-11  222   * @data   Pointer to driver_data.
8f8b8995 Asai Thambi S P 2013-09-11  223   * @status Completion status.
8f8b8995 Asai Thambi S P 2013-09-11  224   *
8f8b8995 Asai Thambi S P 2013-09-11  225   * return value
8f8b8995 Asai Thambi S P 2013-09-11  226   *	None
8f8b8995 Asai Thambi S P 2013-09-11  227   */
8f8b8995 Asai Thambi S P 2013-09-11  228  static void mtip_async_complete(struct mtip_port *port,
ffc771b3 Jens Axboe      2014-05-09  229  				int tag, struct mtip_cmd *cmd, int status)
8f8b8995 Asai Thambi S P 2013-09-11  230  {
6a63892e Heloise         2017-04-25  231  	if (unlikely(!port))
6a63892e Heloise         2017-04-25  232  		return;
6a63892e Heloise         2017-04-25  233  
ffc771b3 Jens Axboe      2014-05-09 @234  	struct driver_data *dd = port->dd;
ffc771b3 Jens Axboe      2014-05-09  235  	struct request *rq;
8f8b8995 Asai Thambi S P 2013-09-11  236  
6a63892e Heloise         2017-04-25  237  	if (unlikely(!dd))
8f8b8995 Asai Thambi S P 2013-09-11  238  		return;
8f8b8995 Asai Thambi S P 2013-09-11  239  
8f8b8995 Asai Thambi S P 2013-09-11  240  	if (unlikely(status == PORT_IRQ_TF_ERR)) {
8f8b8995 Asai Thambi S P 2013-09-11  241  		dev_warn(&port->dd->pdev->dev,
8f8b8995 Asai Thambi S P 2013-09-11  242  			"Command tag %d failed due to TFE\n", tag);

:::::: The code at line 234 was first introduced by commit
:::::: ffc771b3ca8b2c03e5e9faa6335b4862108f111f mtip32xx: convert to use blk-mq

:::::: TO: Jens Axboe <axboe@fb.com>
:::::: CC: Jens Axboe <axboe@fb.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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