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From 55c537734f476d04c18f67083642b96bbead6219 Mon Sep 17 00:00:00 2001
From: Phil Sutter <psutter@redhat.com>
Date: Mon, 27 Jan 2020 16:11:41 +0100
Subject: [PATCH] netlink: Avoid potential NULL-pointer deref in
 netlink_gen_payload_stmt()

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1793030
Upstream Status: nftables commit c9ddf0bff363f

commit c9ddf0bff363fc9101b563b592db600bdf4d65c5
Author: Phil Sutter <phil@nwl.cc>
Date:   Mon Jan 20 16:32:40 2020 +0100

    netlink: Avoid potential NULL-pointer deref in netlink_gen_payload_stmt()

    With payload_needs_l4csum_update_pseudohdr() unconditionally
    dereferencing passed 'desc' parameter and a previous check for it to be
    non-NULL, make sure to call the function only if input is sane.

    Fixes: 68de70f2b3fc6 ("netlink_linearize: fix IPv6 layer 4 checksum mangling")
    Signed-off-by: Phil Sutter <phil@nwl.cc>
    Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 src/netlink_linearize.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c
index 498326d..cb1b7fe 100644
--- a/src/netlink_linearize.c
+++ b/src/netlink_linearize.c
@@ -941,7 +941,7 @@ static void netlink_gen_payload_stmt(struct netlink_linearize_ctx *ctx,
 		nftnl_expr_set_u32(nle, NFTNL_EXPR_PAYLOAD_CSUM_OFFSET,
 				   csum_off / BITS_PER_BYTE);
 	}
-	if (expr->payload.base == PROTO_BASE_NETWORK_HDR &&
+	if (expr->payload.base == PROTO_BASE_NETWORK_HDR && desc &&
 	    payload_needs_l4csum_update_pseudohdr(expr, desc))
 		nftnl_expr_set_u32(nle, NFTNL_EXPR_PAYLOAD_FLAGS,
 				   NFT_PAYLOAD_L4CSUM_PSEUDOHDR);
-- 
1.8.3.1