[PATCH 3.12 40/82] xhci: fix off by one error in TRB DMA address boundary check
From: Jiri Slaby
Date: Mon Aug 24 2015 - 05:25:31 EST
From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
commit 7895086afde2a05fa24a0e410d8e6b75ca7c8fdd upstream.
We need to check that a TRB is part of the current segment
before calculating its DMA address.
Previously a ring segment didn't use a full memory page, and every
new ring segment got a new memory page, so the off by one
error in checking the upper bound was never seen.
Now that we use a full memory page, 256 TRBs (4096 bytes), the off by one
didn't catch the case when a TRB was the first element of the next segment.
This is triggered if the virtual memory pages for a ring segment are
next to each in increasing order where the ring buffer wraps around and
causes errors like:
[ 106.398223] xhci_hcd 0000:00:14.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 0 comp_code 1
[ 106.398230] xhci_hcd 0000:00:14.0: Looking for event-dma fffd3000 trb-start fffd4fd0 trb-end fffd5000 seg-start fffd4000 seg-end fffd4ff0
The trb-end address is one outside the end-seg address.
Tested-by: Arkadiusz MiÅkiewicz <arekm@xxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
drivers/usb/host/xhci-ring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index b16404723fc2..66deb0af258e 100644
@@ -86,7 +86,7 @@ dma_addr_t xhci_trb_virt_to_dma(struct xhci_segment *seg,
/* offset in TRBs */
segment_offset = trb - seg->trbs;
- if (segment_offset > TRBS_PER_SEGMENT)
+ if (segment_offset >= TRBS_PER_SEGMENT)
return seg->dma + (segment_offset * sizeof(*trb));
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