From: Alan Stern <stern@rowland.harvard.edu>
Date: Wed, 12 Nov 2008 22:02:57 +0000 (-0500)
Subject: USB: EHCI: fix divide-by-zero bug
X-Git-Tag: v2.6.27.7~8
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b060be07052aa48ff66879c0c47d40d2bbd2c698;p=thirdparty%2Fkernel%2Fstable.git

USB: EHCI: fix divide-by-zero bug

commit 372dd6e8ed924e876f3beb598721e813ad7fa323 upstream.

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>
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 4a0c5a78b2ed7..a081ee65bde6d 100644
--- 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);