[PATCH v2] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

[PATCH v2] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

[Tuo Li]

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 and call 
transport_kunmap_data_sg() only when buf is not NULL.

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Tuo Li <islituo@gmail.com>
---
v2:
* Put transport_kunmap_data_sg() into the else-branch of the if (!bug).
  Thank Bodo Stroesser for helpful advice.
---
 drivers/target/target_core_pscsi.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 2629d2ef3970..75ef52f008ff 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -620,17 +620,17 @@ 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);
+				transport_kunmap_data_sg(cmd);
+			}
 		}
 	}
 after_mode_sense:
-- 
2.25.1

Re: [PATCH v2] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

[Bodo Stroesser]

On 10.08.21 06:04, 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 and call
> transport_kunmap_data_sg() only when buf is not NULL.
> 
> Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
> Signed-off-by: Tuo Li <islituo@gmail.com>
> ---
> v2:
> * Put transport_kunmap_data_sg() into the else-branch of the if (!bug).
>    Thank Bodo Stroesser for helpful advice.
> ---
>   drivers/target/target_core_pscsi.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
> index 2629d2ef3970..75ef52f008ff 100644
> --- a/drivers/target/target_core_pscsi.c
> +++ b/drivers/target/target_core_pscsi.c
> @@ -620,17 +620,17 @@ 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);
> +				transport_kunmap_data_sg(cmd);
> +			}
>   		}
>   	}
>   after_mode_sense:
> 

Reviewed-by: Bodo Stroesser <bostroesser@gmail.com>

Regards,
Bodo

Re: [PATCH v2] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

[Martin K. Petersen]

Tuo,

> The return value of transport_kmap_data_sg() is assigned to the variable
> buf:

Applied to 5.15/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH v2] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()

[Martin K. Petersen]

On Mon, 9 Aug 2021 21:04:13 -0700, 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) {
> 
> [...]

Applied to 5.15/scsi-queue, thanks!

[1/1] scsi: target: pscsi: Fix possible null-pointer dereference in pscsi_complete_cmd()
      https://git.kernel.org/mkp/scsi/c/0f99792c01d1

-- 
Martin K. Petersen	Oracle Linux Engineering