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

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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 <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
---
  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.



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