tg3: fix length overflow in VPD firmware parsing

commit 715230a44310a8cf66fbfb5a46f9a62a9b2de424 upstream.

Commit 184b89044fb6e2a74611dafa69b1dce0d98612c6 ("tg3: Use VPD fw version
when present") introduced VPD parsing that contained a potential length
overflow.

Limit the hardware's reported firmware string length (max 255 bytes) to
stay inside the driver's firmware string length (32 bytes). On overflow,
truncate the formatted firmware string instead of potentially overwriting
portions of the tg3 struct.

http://cansecwest.com/slides/2013/PrivateCore%20CSW%202013.pdf

Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Oded Horovitz <oded@privatecore.com>
Reported-by: Brad Spengler <spender@grsecurity.net>
Cc: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index c86fa50..c6b9903 100644 (file)
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -13433,8 +13433,11 @@ static void __devinit tg3_read_vpd(struct tg3 *tp)
                if (j + len > block_end)
                        goto partno;
 
-               memcpy(tp->fw_ver, &vpd_data[j], len);
-               strncat(tp->fw_ver, " bc ", vpdlen - len - 1);
+               if (len >= sizeof(tp->fw_ver))
+                       len = sizeof(tp->fw_ver) - 1;
+               memset(tp->fw_ver, 0, sizeof(tp->fw_ver));
+               snprintf(tp->fw_ver, sizeof(tp->fw_ver), "%.*s bc ", len,
+                        &vpd_data[j]);
        }
 
 partno: