[PATCH] usb: storage: initialize variable

[PATCH] usb: storage: initialize variable

[trix]

From: Tom Rix <trix@redhat.com>

clang static analysis reports this representative problem

transport.c:495:15: warning: Assigned value is garbage or
  undefined
        length_left -= partial;
                   ^  ~~~~~~~
partial is set only when usb_stor_bulk_transfer_sglist()
is successful.

So initialize to partial to 0.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 drivers/usb/storage/transport.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index 238a8088e17f..ce920851b1f2 100644
--- a/drivers/usb/storage/transport.c
+++ b/drivers/usb/storage/transport.c
@@ -461,7 +461,7 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe,
 int usb_stor_bulk_srb(struct us_data* us, unsigned int pipe,
 		      struct scsi_cmnd* srb)
 {
-	unsigned int partial;
+	unsigned int partial = 0;
 	int result = usb_stor_bulk_transfer_sglist(us, pipe, scsi_sglist(srb),
 				      scsi_sg_count(srb), scsi_bufflen(srb),
 				      &partial);
@@ -484,7 +484,7 @@ int usb_stor_bulk_transfer_sg(struct us_data* us, unsigned int pipe,
 		void *buf, unsigned int length_left, int use_sg, int *residual)
 {
 	int result;
-	unsigned int partial;
+	unsigned int partial = 0;
 
 	/* are we scatter-gathering? */
 	if (use_sg) {
-- 
2.18.1

Re: [PATCH] usb: storage: initialize variable

[Alan Stern]

On Sat, Aug 22, 2020 at 02:18:39PM -0700, trix@redhat.com wrote:
> From: Tom Rix <trix@redhat.com>
> 
> clang static analysis reports this representative problem
> 
> transport.c:495:15: warning: Assigned value is garbage or
>   undefined
>         length_left -= partial;
>                    ^  ~~~~~~~
> partial is set only when usb_stor_bulk_transfer_sglist()
> is successful.
> 
> So initialize to partial to 0.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  drivers/usb/storage/transport.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
> index 238a8088e17f..ce920851b1f2 100644
> --- a/drivers/usb/storage/transport.c
> +++ b/drivers/usb/storage/transport.c
> @@ -461,7 +461,7 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe,
>  int usb_stor_bulk_srb(struct us_data* us, unsigned int pipe,
>  		      struct scsi_cmnd* srb)
>  {
> -	unsigned int partial;
> +	unsigned int partial = 0;
>  	int result = usb_stor_bulk_transfer_sglist(us, pipe, scsi_sglist(srb),
>  				      scsi_sg_count(srb), scsi_bufflen(srb),
>  				      &partial);
> @@ -484,7 +484,7 @@ int usb_stor_bulk_transfer_sg(struct us_data* us, unsigned int pipe,
>  		void *buf, unsigned int length_left, int use_sg, int *residual)
>  {
>  	int result;
> -	unsigned int partial;
> +	unsigned int partial = 0;
>  
>  	/* are we scatter-gathering? */
>  	if (use_sg) {

Yes, this is a bug.  But the right way to fix it is to change 
usb_stor_bulk_transfer_sglist(): Make it store 0 to *act_len at the 
start.

That way you change only one localized piece of code, instead of 
changing multiple callers and leaving a possibility of more errors being 
added in the future.

Alan Stern

Re: [PATCH] usb: storage: initialize variable

[Tom Rix]

On 8/22/20 5:49 PM, Alan Stern wrote:
> On Sat, Aug 22, 2020 at 02:18:39PM -0700, trix@redhat.com wrote:
>> From: Tom Rix <trix@redhat.com>
>>
>> clang static analysis reports this representative problem
>>
>> transport.c:495:15: warning: Assigned value is garbage or
>>   undefined
>>         length_left -= partial;
>>                    ^  ~~~~~~~
>> partial is set only when usb_stor_bulk_transfer_sglist()
>> is successful.
>>
>> So initialize to partial to 0.
>>
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Tom Rix <trix@redhat.com>
>> ---
>>  drivers/usb/storage/transport.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
>> index 238a8088e17f..ce920851b1f2 100644
>> --- a/drivers/usb/storage/transport.c
>> +++ b/drivers/usb/storage/transport.c
>> @@ -461,7 +461,7 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe,
>>  int usb_stor_bulk_srb(struct us_data* us, unsigned int pipe,
>>  		      struct scsi_cmnd* srb)
>>  {
>> -	unsigned int partial;
>> +	unsigned int partial = 0;
>>  	int result = usb_stor_bulk_transfer_sglist(us, pipe, scsi_sglist(srb),
>>  				      scsi_sg_count(srb), scsi_bufflen(srb),
>>  				      &partial);
>> @@ -484,7 +484,7 @@ int usb_stor_bulk_transfer_sg(struct us_data* us, unsigned int pipe,
>>  		void *buf, unsigned int length_left, int use_sg, int *residual)
>>  {
>>  	int result;
>> -	unsigned int partial;
>> +	unsigned int partial = 0;
>>  
>>  	/* are we scatter-gathering? */
>>  	if (use_sg) {
> Yes, this is a bug.  But the right way to fix it is to change 
> usb_stor_bulk_transfer_sglist(): Make it store 0 to *act_len at the 
> start.
>
> That way you change only one localized piece of code, instead of 
> changing multiple callers and leaving a possibility of more errors being 
> added in the future.

I'll respin the patch.

It will exchange the compile time initialization fix for a run time if-check fix.

> Alan Stern
>