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

[Tuo Li]

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 <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.