linux-kernel - [PATCH 5.10 081/100] net: ipv4: Fix the warning for dereference

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Message-Id: <20220131105223.166114763@linuxfoundation.org>
Date:   Mon, 31 Jan 2022 11:56:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Yajun Deng <yajun.deng@...ux.dev>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 081/100] net: ipv4: Fix the warning for dereference

From: Yajun Deng <yajun.deng@...ux.dev>

[ Upstream commit 1b9fbe813016b08e08b22ddba4ddbf9cb1b04b00 ]

Add a if statements to avoid the warning.

Dan Carpenter report:
The patch faf482ca196a: "net: ipv4: Move ip_options_fragment() out of
loop" from Aug 23, 2021, leads to the following Smatch complaint:

    net/ipv4/ip_output.c:833 ip_do_fragment()
    warn: variable dereferenced before check 'iter.frag' (see line 828)

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: faf482ca196a ("net: ipv4: Move ip_options_fragment() out of loop")
Link: https://lore.kernel.org/netdev/20210830073802.GR7722@kadam/T/#t
Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv4/ip_output.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index fb91a466b2d34..e77afaecc9818 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -833,7 +833,9 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 
 		/* Everything is OK. Generate! */
 		ip_fraglist_init(skb, iph, hlen, &iter);
-		ip_options_fragment(iter.frag);
+
+		if (iter.frag)
+			ip_options_fragment(iter.frag);
 
 		for (;;) {
 			/* Prepare header of the next frame,
-- 
2.34.1