2021-12-24 12:02:30

by Yue Haibing

Subject: [PATCH -next] scsi: storvsc: Fix unsigned comparison to zero

The unsigned variable sg_count is being assigned a return value
from the call to scsi_dma_map() that can return -ENOMEM.

Fixes: 743b237c3a7b ("scsi: storvsc: Add Isolation VM support for storvsc driver")
Signed-off-by: YueHaibing <[email protected]>
---
drivers/scsi/storvsc_drv.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index ae293600d799..072c752a8c36 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1837,7 +1837,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
struct scatterlist *sg;
unsigned long hvpfn, hvpfns_to_add;
- int j, i = 0;
+ int sg_cnt, j, i = 0;

if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {

@@ -1851,11 +1851,11 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
payload->range.len = length;
payload->range.offset = offset_in_hvpg;

- sg_count = scsi_dma_map(scmnd);
- if (sg_count < 0)
+ sg_cnt = scsi_dma_map(scmnd);
+ if (sg_cnt < 0)
return SCSI_MLQUEUE_DEVICE_BUSY;

- for_each_sg(sgl, sg, sg_count, j) {
+ for_each_sg(sgl, sg, sg_cnt, j) {
/*
* Init values for the current sgl entry. hvpfns_to_add
* is in units of Hyper-V size pages. Handling the
--
2.17.1

2021-12-26 19:49:49

by Michael Kelley (LINUX)

Subject: RE: [PATCH -next] scsi: storvsc: Fix unsigned comparison to zero

From: YueHaibing <[email protected]> Sent: Friday, December 24, 2021 4:02 AM
>
> The unsigned variable sg_count is being assigned a return value
> from the call to scsi_dma_map() that can return -ENOMEM.
>
> Fixes: 743b237c3a7b ("scsi: storvsc: Add Isolation VM support for storvsc driver")
> Signed-off-by: YueHaibing <[email protected]>

Good catch! But I wonder if a simpler fix is to just remove the "unsigned"
from the declaration of sg_count. Then we don't need to add the
sg_cnt local variable. A little less complexity is almost always better. :-)

Michael

> ---
> drivers/scsi/storvsc_drv.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index ae293600d799..072c752a8c36 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1837,7 +1837,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
> unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
> struct scatterlist *sg;
> unsigned long hvpfn, hvpfns_to_add;
> - int j, i = 0;
> + int sg_cnt, j, i = 0;
>
> if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
>
> @@ -1851,11 +1851,11 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
> payload->range.len = length;
> payload->range.offset = offset_in_hvpg;
>
> - sg_count = scsi_dma_map(scmnd);
> - if (sg_count < 0)
> + sg_cnt = scsi_dma_map(scmnd);
> + if (sg_cnt < 0)
> return SCSI_MLQUEUE_DEVICE_BUSY;
>
> - for_each_sg(sgl, sg, sg_count, j) {
> + for_each_sg(sgl, sg, sg_cnt, j) {
> /*
> * Init values for the current sgl entry. hvpfns_to_add
> * is in units of Hyper-V size pages. Handling the
> --
> 2.17.1

2021-12-27 04:04:36

by Yue Haibing

Subject: Re: [PATCH -next] scsi: storvsc: Fix unsigned comparison to zero

On 2021/12/27 3:49, Michael Kelley (LINUX) wrote:
> From: YueHaibing <[email protected]> Sent: Friday, December 24, 2021 4:02 AM
>>
>> The unsigned variable sg_count is being assigned a return value
>> from the call to scsi_dma_map() that can return -ENOMEM.
>>
>> Fixes: 743b237c3a7b ("scsi: storvsc: Add Isolation VM support for storvsc driver")
>> Signed-off-by: YueHaibing <[email protected]>
>
> Good catch! But I wonder if a simpler fix is to just remove the "unsigned"
> from the declaration of sg_count. Then we don't need to add the
> sg_cnt local variable. A little less complexity is almost always better. :-)

Ok， will respine
>
> Michael
>
>> ---
>> drivers/scsi/storvsc_drv.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
>> index ae293600d799..072c752a8c36 100644
>> --- a/drivers/scsi/storvsc_drv.c
>> +++ b/drivers/scsi/storvsc_drv.c
>> @@ -1837,7 +1837,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
>> unsigned int hvpg_count = HVPFN_UP(offset_in_hvpg + length);
>> struct scatterlist *sg;
>> unsigned long hvpfn, hvpfns_to_add;
>> - int j, i = 0;
>> + int sg_cnt, j, i = 0;
>>
>> if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
>>
>> @@ -1851,11 +1851,11 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
>> payload->range.len = length;
>> payload->range.offset = offset_in_hvpg;
>>
>> - sg_count = scsi_dma_map(scmnd);
>> - if (sg_count < 0)
>> + sg_cnt = scsi_dma_map(scmnd);
>> + if (sg_cnt < 0)
>> return SCSI_MLQUEUE_DEVICE_BUSY;
>>
>> - for_each_sg(sgl, sg, sg_count, j) {
>> + for_each_sg(sgl, sg, sg_cnt, j) {
>> /*
>> * Init values for the current sgl entry. hvpfns_to_add
>> * is in units of Hyper-V size pages. Handling the
>> --
>> 2.17.1
>
> .
>