From 574fa55c2e70449887c7714d7b043f4e8b6d28da Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw@strlen.de>
Date: Fri, 14 Jul 2023 16:53:57 +0200
Subject: [PATCH] exthdr: prefer raw_type instead of desc->type

On ancient kernels desc can be NULL, because such kernels do not
understand NFTA_EXTHDR_TYPE.

Thus they don't include it in the reverse dump, so the tcp/ip
option gets treated like an ipv6 exthdr, but no matching
description will be found.

This then gives a crash due to the null deref.

Just use the raw value here, this avoid a crash and at least
print *something*, e.g.:

unknown-exthdr unknown & 0xf0 [invalid type] == 0x0 [invalid type]

Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/exthdr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/exthdr.c b/src/exthdr.c
index f5527ddb..0358005b 100644
--- a/src/exthdr.c
+++ b/src/exthdr.c
@@ -405,7 +405,7 @@ bool exthdr_find_template(struct expr *expr, const struct expr *mask, unsigned i
 		found = tcpopt_find_template(expr, off, mask_len - mask_offset);
 		break;
 	case NFT_EXTHDR_OP_IPV6:
-		exthdr_init_raw(expr, expr->exthdr.desc->type,
+		exthdr_init_raw(expr, expr->exthdr.raw_type,
 				off, mask_len - mask_offset, expr->exthdr.op, 0);
 
 		/* still failed to find a template... Bug. */
-- 
2.33.0