2021-08-07 13:52:26

by Tuo Li

Subject: [PATCH] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

The return value of transport_kmap_data_sg() is assigned to the variable
buf:
buf = transport_kmap_data_sg(cmd);

And then it is checked:
if (!buf) {

This indicates that buf can be NULL. However, it is dereferenced in the
following statements:
if (!(buf[3] & 0x80))
buf[3] |= 0x80;
if (!(buf[2] & 0x80))
buf[2] |= 0x80;

To fix these possible null-pointer dereferences, dereference buf only when
it is not NULL.

Reported-by: TOTE Robot <[email protected]>
Signed-off-by: Tuo Li <[email protected]>
---
drivers/target/target_core_pscsi.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 2629d2ef3970..560815729182 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -620,14 +620,14 @@ static void pscsi_complete_cmd(struct se_cmd *cmd, u8 scsi_status,
buf = transport_kmap_data_sg(cmd);
if (!buf) {
; /* XXX: TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE */
- }
-
- if (cdb[0] == MODE_SENSE_10) {
- if (!(buf[3] & 0x80))
- buf[3] |= 0x80;
} else {
- if (!(buf[2] & 0x80))
- buf[2] |= 0x80;
+ if (cdb[0] == MODE_SENSE_10) {
+ if (!(buf[3] & 0x80))
+ buf[3] |= 0x80;
+ } else {
+ if (!(buf[2] & 0x80))
+ buf[2] |= 0x80;
+ }
}

transport_kunmap_data_sg(cmd);
--
2.25.1

2021-08-09 10:51:27

by Bodo Stroesser

Subject: Re: [PATCH] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

On 07.08.21 15:46, Tuo Li wrote:
> The return value of transport_kmap_data_sg() is assigned to the variable
> buf:
> buf = transport_kmap_data_sg(cmd);
>
> And then it is checked:
> if (!buf) {
>
> This indicates that buf can be NULL. However, it is dereferenced in the
> following statements:
> if (!(buf[3] & 0x80))
> buf[3] |= 0x80;
> if (!(buf[2] & 0x80))
> buf[2] |= 0x80;
>
> To fix these possible null-pointer dereferences, dereference buf only when
> it is not NULL.
>
> Reported-by: TOTE Robot <[email protected]>
> Signed-off-by: Tuo Li <[email protected]>
> ---
> drivers/target/target_core_pscsi.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
> index 2629d2ef3970..560815729182 100644
> --- a/drivers/target/target_core_pscsi.c
> +++ b/drivers/target/target_core_pscsi.c
> @@ -620,14 +620,14 @@ static void pscsi_complete_cmd(struct se_cmd *cmd, u8 scsi_status,
> buf = transport_kmap_data_sg(cmd);
> if (!buf) {
> ; /* XXX: TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE */
> - }
> -
> - if (cdb[0] == MODE_SENSE_10) {
> - if (!(buf[3] & 0x80))
> - buf[3] |= 0x80;
> } else {
> - if (!(buf[2] & 0x80))
> - buf[2] |= 0x80;
> + if (cdb[0] == MODE_SENSE_10) {
> + if (!(buf[3] & 0x80))
> + buf[3] |= 0x80;
> + } else {
> + if (!(buf[2] & 0x80))
> + buf[2] |= 0x80;
> + }
> }
>
> transport_kunmap_data_sg(cmd);
>

I'm wondering whether we should better put the
transport_kunmap_data_sg into the else-branch of the if (!buf)?
AFAICS, calling it after transport_kmap_data_sg failed does not
cause problems, but I feel it would be cleaner.

Otherwise it looks good to me.

2021-08-09 12:40:51

by Tuo Li

Subject: Re: [PATCH] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

Thanks for your feedback. We will prepare a V2 patch and put the
transport_kunmap_data_sg()
into the else-branch of the if (!buf).

Best wishes,
Tuo Li

On 2021/8/9 18:36, Bodo Stroesser wrote:
> On 07.08.21 15:46, Tuo Li wrote:
>> The return value of transport_kmap_data_sg() is assigned to the variable
>> buf:
>>    buf = transport_kmap_data_sg(cmd);
>>
>> And then it is checked:
>>    if (!buf) {
>>
>> This indicates that buf can be NULL. However, it is dereferenced in the
>> following statements:
>>    if (!(buf[3] & 0x80))
>>      buf[3] |= 0x80;
>>    if (!(buf[2] & 0x80))
>>     buf[2] |= 0x80;
>>
>> To fix these possible null-pointer dereferences, dereference buf only
>> when
>> it is not NULL.
>>
>> Reported-by: TOTE Robot <[email protected]>
>> Signed-off-by: Tuo Li <[email protected]>
>> ---
>>   drivers/target/target_core_pscsi.c | 14 +++++++-------
>>   1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/target/target_core_pscsi.c
>> b/drivers/target/target_core_pscsi.c
>> index 2629d2ef3970..560815729182 100644
>> --- a/drivers/target/target_core_pscsi.c
>> +++ b/drivers/target/target_core_pscsi.c
>> @@ -620,14 +620,14 @@ static void pscsi_complete_cmd(struct se_cmd
>> *cmd, u8 scsi_status,
>>               buf = transport_kmap_data_sg(cmd);
>>               if (!buf) {
>>                   ; /* XXX: TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE */
>> -            }
>> -
>> -            if (cdb[0] == MODE_SENSE_10) {
>> -                if (!(buf[3] & 0x80))
>> -                    buf[3] |= 0x80;
>>               } else {
>> -                if (!(buf[2] & 0x80))
>> -                    buf[2] |= 0x80;
>> +                if (cdb[0] == MODE_SENSE_10) {
>> +                    if (!(buf[3] & 0x80))
>> +                        buf[3] |= 0x80;
>> +                } else {
>> +                    if (!(buf[2] & 0x80))
>> +                        buf[2] |= 0x80;
>> +                }
>>               }
>>                 transport_kunmap_data_sg(cmd);
>>
>
> I'm wondering whether we should better put the
> transport_kunmap_data_sg into the else-branch of the if (!buf)?
> AFAICS, calling it after transport_kmap_data_sg failed does not
> cause problems, but I feel it would be cleaner.
>
> Otherwise it looks good to me.