tg3: fix length overflow in VPD firmware parsing

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: stable@vger.kernel.org
Cc: Matt Carlson <mcarlson@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index 67d2663b3974aeaf03acfeb9500704ee5659ab8a..17a972734ba746d9218df4bf025218a91ebee947 100644 (file)
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -14604,8 +14604,11 @@ static void 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: