netfilter: nf_conntrack_h323: restore boundary check correctness

[ Upstream commit f5e85ce8e733c2547827f6268136b70b802eabdb ]

Since commit bc7d811a ("netfilter: nf_ct_h323: Convert
CHECK_BOUND macro to function"), NAT traversal for H.323
doesn't work, failing to parse H323-UserInformation.
nf_h323_error_boundary() compares contents of the bitstring,
not the addresses, preventing valid H.323 packets from being
conntrack'd.

This looks like an oversight from when CHECK_BOUND macro was
converted to a function.

To fix it, stop dereferencing bs->cur and bs->end.

Fixes: bc7d811a ("netfilter: nf_ct_h323: Convert CHECK_BOUND macro to function")
Signed-off-by: NJakub Jankowski <shasta@toxcorp.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>

net/netfilter/nf_conntrack_h323_asn1.c

@@ -172,7 +172,7 @@ static int nf_h323_error_boundary(struct bitstr *bs, size_t bytes, size_t bits)
 	if (bits % BITS_PER_BYTE > 0)
 		bytes++;
 
-	if (*bs->cur + bytes > *bs->end)
+	if (bs->cur + bytes > bs->end)
 		return 1;
 
 	return 0;