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 ([PATCH] b44: add wol for old nic) on 2006-06-20.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/b44.c b/drivers/net/b44.c
index 2a9132343b66135fb2487c30a20ba6ce0db786ec..4869adb695865a3f7dc4ff3bacd1ee5a260b296d 100644 (file)
--- 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;