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SubjectRe: [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@tsinghua.edu.cn>
> Signed-off-by: Tuo Li <islituo@gmail.com>
> ---
> 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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