libata: add SG safety checks in SFF pio transfers

Abort processing of a command if we run out of mapped data in the
SG list. This should never happen, but a previous bug caused it to
be possible. Play it safe and attempt to abort nicely if we don't
have more SG segments left.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
index 10aa278..4f115ad 100644 (file)
--- a/drivers/ata/libata-sff.c
+++ b/drivers/ata/libata-sff.c
@@ -658,6 +658,10 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
        unsigned int offset;
        unsigned char *buf;
 
+       if (!qc->cursg) {
+               qc->curbytes = qc->nbytes;
+               return;
+       }
        if (qc->curbytes == qc->nbytes - qc->sect_size)
                ap->hsm_task_state = HSM_ST_LAST;
 
@@ -683,6 +687,8 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
 
        if (qc->cursg_ofs == qc->cursg->length) {
                qc->cursg = sg_next(qc->cursg);
+               if (!qc->cursg)
+                       ap->hsm_task_state = HSM_ST_LAST;
                qc->cursg_ofs = 0;
        }
 }