[PATCH] scsi: Fix a harmless double shift bug

[PATCH] scsi: Fix a harmless double shift bug

[Dan Carpenter]

Smatch generates a warning:

    drivers/scsi/scsi_lib.c:1656 scsi_mq_done() warn: test_bit() takes a bit number

The problem is that SCMD_STATE_COMPLETE is supposed to be bit number 0
and not a mask like "(1 << 0)".  It is used like this:

	if (test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state))

The test_and_set_bit() has a shift built in so it's a double left shift
and uses bit number 1 instead of number 0.  This bug is harmless because
it's done consistently and it doesn't clash with any other flags.

Fixes: f1342709d18a ("scsi: Do not rely on blk-mq for double completions")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 include/scsi/scsi_cmnd.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 3de905e205ce..d85e6befa26b 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -62,7 +62,7 @@ struct scsi_pointer {
 #define SCMD_PRESERVED_FLAGS	(SCMD_UNCHECKED_ISA_DMA | SCMD_INITIALIZED)
 
 /* for scmd->state */
-#define SCMD_STATE_COMPLETE	(1 << 0)
+#define SCMD_STATE_COMPLETE	0
 
 struct scsi_cmnd {
 	struct scsi_request req;
-- 
2.11.0

Re: [PATCH] scsi: Fix a harmless double shift bug

[Keith Busch]

On Thu, Nov 29, 2018 at 01:37:10PM +0300, Dan Carpenter wrote:
> Smatch generates a warning:
> 
>     drivers/scsi/scsi_lib.c:1656 scsi_mq_done() warn: test_bit() takes a bit number
> 
> The problem is that SCMD_STATE_COMPLETE is supposed to be bit number 0
> and not a mask like "(1 << 0)".  It is used like this:
> 
> 	if (test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state))
> 
> The test_and_set_bit() has a shift built in so it's a double left shift
> and uses bit number 1 instead of number 0.  This bug is harmless because
> it's done consistently and it doesn't clash with any other flags.
> 
> Fixes: f1342709d18a ("scsi: Do not rely on blk-mq for double completions")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Nice catch, thanks for the fix.

Reviewed-by: Keith Busch <keith.busch@intel.com>

Re: [PATCH] scsi: Fix a harmless double shift bug

[Martin K. Petersen]

Jens,

This went in through your tree. Can you please pick this fix up?

> On Thu, Nov 29, 2018 at 01:37:10PM +0300, Dan Carpenter wrote:
>> Smatch generates a warning:
>> 
>>     drivers/scsi/scsi_lib.c:1656 scsi_mq_done() warn: test_bit() takes a bit number
>> 
>> The problem is that SCMD_STATE_COMPLETE is supposed to be bit number 0
>> and not a mask like "(1 << 0)".  It is used like this:
>> 
>> 	if (test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state))
>> 
>> The test_and_set_bit() has a shift built in so it's a double left shift
>> and uses bit number 1 instead of number 0.  This bug is harmless because
>> it's done consistently and it doesn't clash with any other flags.
>> 
>> Fixes: f1342709d18a ("scsi: Do not rely on blk-mq for double completions")
>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> Nice catch, thanks for the fix.
>
> Reviewed-by: Keith Busch <keith.busch@intel.com>

Acked-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH] scsi: Fix a harmless double shift bug

[Jens Axboe]

On 12/7/18 8:20 PM, Martin K. Petersen wrote:
> 
> Jens,
> 
> This went in through your tree. Can you please pick this fix up?

Yep, applied, thanks Dan.

-- 
Jens Axboe