netdev - [PATCH v2 1/2] cipso: fix total option length computation

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Date: Fri,  7 Jun 2024 18:07:52 +0200
From: Ondrej Mosnacek <omosnace@...hat.com>
To: Paul Moore <paul@...l-moore.com>
Cc: netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: [PATCH v2 1/2] cipso: fix total option length computation

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 IPOPT_END into account.

Fix it by recognizing the IPOPT_END value as the end of actual options.

Fixes: 014ab19a69c3 ("selinux: Set socket NetLabel based on connection endpoint")
Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
---
 net/ipv4/cipso_ipv4.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index dd6d460150580..5e9ac68444f89 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -2013,12 +2013,16 @@ 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) {
+		while (iter < opt->opt.optlen) {
+			if (opt->opt.__data[iter] == IPOPT_END) {
+				break;
+			} else if (opt->opt.__data[iter] == IPOPT_NOP) {
+				iter++;
+			} else {
 				iter += opt->opt.__data[iter + 1];
 				optlen_new = iter;
-			} else
-				iter++;
+			}
+		}
 		hdr_delta = opt->opt.optlen;
 		opt->opt.optlen = (optlen_new + 3) & ~3;
 		hdr_delta -= opt->opt.optlen;
-- 
2.45.1