netdev - [PATCH v2 net 1/4] xfrm: Don't accidentally set RTO_ONLINK in decode

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Date:   Mon, 10 Jan 2022 14:43:06 +0100
From:   Guillaume Nault <gnault@...hat.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH v2 net 1/4] xfrm: Don't accidentally set RTO_ONLINK in
 decode_session4()

Similar to commit 94e2238969e8 ("xfrm4: strip ECN bits from tos field"),
clear the ECN bits from iph->tos when setting ->flowi4_tos.
This ensures that the last bit of ->flowi4_tos is cleared, so
ip_route_output_key_hash() isn't going to restrict the scope of the
route lookup.

Use ~INET_ECN_MASK instead of IPTOS_RT_MASK, because we have no reason
to clear the high order bits.

Found by code inspection, compile tested only.

Fixes: 4da3089f2b58 ("[IPSEC]: Use TOS when doing tunnel lookups")
Signed-off-by: Guillaume Nault <gnault@...hat.com>
---
 net/xfrm/xfrm_policy.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 84d2361da015..4924b9135c6e 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -31,6 +31,7 @@
 #include <linux/if_tunnel.h>
 #include <net/dst.h>
 #include <net/flow.h>
+#include <net/inet_ecn.h>
 #include <net/xfrm.h>
 #include <net/ip.h>
 #include <net/gre.h>
@@ -3295,7 +3296,7 @@ decode_session4(struct sk_buff *skb, struct flowi *fl, bool reverse)
 	fl4->flowi4_proto = iph->protocol;
 	fl4->daddr = reverse ? iph->saddr : iph->daddr;
 	fl4->saddr = reverse ? iph->daddr : iph->saddr;
-	fl4->flowi4_tos = iph->tos;
+	fl4->flowi4_tos = iph->tos & ~INET_ECN_MASK;
 
 	if (!ip_is_fragment(iph)) {
 		switch (iph->protocol) {
-- 
2.21.3