netdev - [PATCH net] hsr: Prevent use after free in prp_create_tagged

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Message-ID: <57af1f28-7f57-4a96-bcd3-b7a0f2340845@moroto.mountain>
Date: Fri, 27 Oct 2023 15:19:01 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Murali Karicheri <m-karicheri2@...com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	YueHaibing <yuehaibing@...wei.com>,
	Ziyang Xuan <william.xuanziyang@...wei.com>, netdev@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [PATCH net] hsr: Prevent use after free in prp_create_tagged_frame()

The prp_fill_rct() function can fail.  In that situation, it frees the
skb and returns NULL.  Meanwhile on the success path, it returns the
original skb.  So it's straight forward to fix bug by using the returned
value.

Fixes: 451d8123f897 ("net: prp: add packet handling support")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 net/hsr/hsr_forward.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index b71dab630a87..80cdc6f6b34c 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -342,9 +342,7 @@ struct sk_buff *prp_create_tagged_frame(struct hsr_frame_info *frame,
 	skb = skb_copy_expand(frame->skb_std, 0,
 			      skb_tailroom(frame->skb_std) + HSR_HLEN,
 			      GFP_ATOMIC);
-	prp_fill_rct(skb, frame, port);
-
-	return skb;
+	return prp_fill_rct(skb, frame, port);
 }
 
 static void hsr_deliver_master(struct sk_buff *skb, struct net_device *dev,
-- 
2.42.0