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Sarah Sharp authored
The length of the scatter gather list a driver can enqueue is limited by the bus' sg_tablesize to 62 entries. Each entry will be described by at least one transfer request block (TRB). If the entry's buffer crosses a 64KB boundary, then that entry will have to be described by two or more TRBs. So even if the USB device driver respects sg_tablesize, the whole scatter list may take more than 62 TRBs to describe, and won't fit on the ring. Don't assume that an empty ring means there is enough room on the transfer ring. The old code would unconditionally queue this too-large transfer, and over write the beginning of the transfer. This would mean the cycle bit was unchanged in those overwritten transfers, causing the hardware to think it didn't own the TRBs, and the host would seem to hang. Now drivers may see submit_urb() fail with -ENOMEM if the transfers are too big to fit on the ring. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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