linux-kernel - [PATCH][stable] b44 WOL setup: one-bit-off stack corruption kernel panic fix

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Date:	Wed, 02 Dec 2009 14:45:47 +0100
From:	Stanislav Brabec <sbrabec@...e.cz>
To:	Gary Zambrano <zambrano@...adcom.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH][stable] b44 WOL setup: one-bit-off stack corruption kernel
 panic fix

About 50% of shutdowns of b44 Ethernet adapter ends by kernel panic with
kernels compiled with stack-protector.

Checking b44_magic_pattern() return values, one call of
b44_magic_pattern() returns 127. It means, that set_bit(128, pmask) was
called on line 1509. It means that bit 0 of 17th byte of pmask was
overwritten. But pmask has only 16 bytes. Stack corruption happens.

It seems that set_bit() on line 1509 always writes one bit off.

The fix does not only solve the stack corruption, but also makes Wake On
LAN working on my onboard B44 on Asus A7V-333X mainboard.

It seems that this problem affects all kernel versions since commit
725ad800 on 2006-06-20.

Signed-off-by: Stanislav Brabec <sbrabec@...e.cz>

diff --git a/drivers/net/b44.c b/drivers/net/b44.c
index 2a91323..4869adb 100644
--- a/drivers/net/b44.c
+++ b/drivers/net/b44.c
@@ -1505,8 +1505,7 @@ static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset)
 		for (k = 0; k< ethaddr_bytes; k++) {
 			ppattern[offset + magicsync +
 				(j * ETH_ALEN) + k] = macaddr[k];
-			len++;
-			set_bit(len, (unsigned long *) pmask);
+			set_bit(len++, (unsigned long *) pmask);
 		}
 	}
 	return len - 1;

-- 
Best Regards / S pozdravem,

Stanislav Brabec
software developer
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