| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 055/130] xhci: fix off by one error in TRB DMA address boundary check | Date | Fri, 4 Sep 2015 14:07:23 +0100 |
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3.16.7-ckt17 -stable review patch. If anyone has any objections, please let me know.
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From: Mathias Nyman <mathias.nyman@linux.intel.com>
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 Miśkiewicz <arekm@maven.pl> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- 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 3f40772962ec..735659f69599 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -82,7 +82,7 @@ dma_addr_t xhci_trb_virt_to_dma(struct xhci_segment *seg, return 0; /* offset in TRBs */ segment_offset = trb - seg->trbs; - if (segment_offset > TRBS_PER_SEGMENT) + if (segment_offset >= TRBS_PER_SEGMENT) return 0; return seg->dma + (segment_offset * sizeof(*trb)); }
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