net ax25: Fix signed comparison in the sockopt handler

fixed upstream in commit b7058842c940ad2c08dd829b21e5c92ebe3b8758 in a different way

The ax25 code tried to use

        if (optlen < sizeof(int))
                return -EINVAL;

as a security check against optlen being negative (or zero) in the
set socket option.

Unfortunately, "sizeof(int)" is an unsigned property, with the
result that the whole comparison is done in unsigned, letting
negative values slip through.

This patch changes this to

        if (optlen < (int)sizeof(int))
                return -EINVAL;

so that the comparison is done as signed, and negative values
get properly caught.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index da0f64f82b5771f65ada62e157b042119ade99b8..f03529cabcb02497ff316cc14ae32de7c3c09cb1 100644 (file)
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -538,7 +538,7 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname,
        if (level != SOL_AX25)
                return -ENOPROTOOPT;
 
-       if (optlen < sizeof(int))
+       if (optlen < (int)sizeof(int))
                return -EINVAL;
 
        if (get_user(opt, (int __user *)optval))