USB: EHCI: fix divide-by-zero bug

This patch (as1164) fixes a bug in the EHCI scheduler.  The interval
value it uses is already in linear format, not logarithmically coded.
The existing code can sometimes crash the system by trying to divide
by zero.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <david-b@pacbell.net>
Cc: Stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 4a0c5a78b2ed74358055e800d5181b1a1e2cb1c7..a081ee65bde6d933f3f2000c67028d461ece27c7 100644 (file)
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -918,7 +918,7 @@ iso_stream_init (
                 */
                stream->usecs = HS_USECS_ISO (maxp);
                bandwidth = stream->usecs * 8;
-               bandwidth /= 1 << (interval - 1);
+               bandwidth /= interval;
 
        } else {
                u32             addr;
@@ -951,7 +951,7 @@ iso_stream_init (
                } else
                        stream->raw_mask = smask_out [hs_transfers - 1];
                bandwidth = stream->usecs + stream->c_usecs;
-               bandwidth /= 1 << (interval + 2);
+               bandwidth /= interval << 3;
 
                /* stream->splits gets created from raw_mask later */
                stream->address = cpu_to_hc32(ehci, addr);