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

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Date:	Thu, 03 Dec 2009 15:56:28 +0100
From:	Stanislav Brabec <sbrabec@...e.cz>
To:	David Miller <davem@...emloft.net>
Cc:	zambrano@...adcom.com, linux-kernel@...r.kernel.org,
	stable@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH][stable] b44 WOL setup: one-bit-off stack corruption
 kernel panic fix

David Miller wrote:
> From: Stanislav Brabec <sbrabec@...e.cz>
> Date: Wed, 02 Dec 2009 15:35:20 +0100
> >> 
> >> It seems that this problem affects all kernel versions since commit
> >> 725ad800 on 2006-06-20.
> > 
> > stable@...nel.org may be interested as well. Adding Cc:.
> 
> netdev@...r.kernel.org is even more interested.  Please post all
> networking patches CC:'d there so they get properly logged
> and tracked in patchwork.

OK, sending again with another Cc::

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>
Cc: netdev@...r.kernel.org
Cc: stable@...nel.org
Cc: Gary Zambrano <zambrano@...adcom.com>

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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