[PATCH 1/2] cipso: fix total option length computation

[Ondrej Mosnacek]

As evident from the definition of ip_options_get(), the IP option
IPOPT_END is used to pad the IP option data array, not IPOPT_NOP. Yet
the loop that walks the IP options to determine the total IP options
length in cipso_v4_delopt() doesn't take it into account.

Fix it by recognizing the IPOPT_END value as the end of actual options.
Also add safety checks in case the options are invalid/corrupted.

Fixes: 014ab19a69c3 ("selinux: Set socket NetLabel based on connection endpoint")
Signed-off-by: Ondrej Mosnacek <omosnace at redhat.com>
---
 net/ipv4/cipso_ipv4.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 8b17d83e5fde4..75b5e3c35f9bf 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -2012,12 +2012,21 @@ static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
 		 * from there we can determine the new total option length */
 		iter = 0;
 		optlen_new = 0;
-		while (iter < opt->opt.optlen)
-			if (opt->opt.__data[iter] != IPOPT_NOP) {
-				iter += opt->opt.__data[iter + 1];
-				optlen_new = iter;
-			} else
+		while (iter < opt->opt.optlen) {
+			if (opt->opt.__data[iter] == IPOPT_END) {
+				break;
+			} else if (opt->opt.__data[iter] == IPOPT_NOP) {
 				iter++;
+			} else {
+				if (WARN_ON(opt->opt.__data[iter + 1] < 2))
+					iter += 2;
+				else
+					iter += opt->opt.__data[iter + 1];
+				optlen_new = iter;
+			}
+		}
+		if (WARN_ON(optlen_new > opt->opt.optlen))
+			optlen_new = opt->opt.optlen;
 		hdr_delta = opt->opt.optlen;
 		opt->opt.optlen = (optlen_new + 3) & ~3;
 		hdr_delta -= opt->opt.optlen;
-- 
2.44.0