firewire: fw-sbp2: add a boundary check

Add rudimentary check for the case that the page table overflows due to
merging of s/g elements by the IOMMU.  This would have lead to
overwriting of arbitrary memory.

After this change I expect that an offending command will be
unsuccessfully retried until the scsi_device is taken offline by SCSI
core.  It's a border case and not worth to implement a recovery
strategy.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Kristian Høgsberg <krh@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
index 212674d723e3..c7518ea4c8ee 100644
--- a/drivers/firewire/fw-sbp2.c
+++ b/drivers/firewire/fw-sbp2.c
@@ -937,6 +937,11 @@ static int sbp2_command_orb_map_scatterlist(struct sbp2_command_orb *orb)
                 sg_len = sg_dma_len(sg + i);
                 sg_addr = sg_dma_address(sg + i);
                 while (sg_len) {
+                        /* FIXME: This won't get us out of the pinch. */
+                        if (unlikely(j >= ARRAY_SIZE(orb->page_table))) {
+                                fw_error("page table overflow\n");
+                                goto fail_page_table;
+                        }
                         l = min(sg_len, SBP2_MAX_SG_ELEMENT_LENGTH);
                         orb->page_table[j].low = sg_addr;
                         orb->page_table[j].high = (l << 16);