linux-kernel - [PATCH net] net: fix skb leak in __skb_tstamp

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Message-ID: <20230522153020.32422-1-ptyadav@amazon.de>
Date:   Mon, 22 May 2023 17:30:20 +0200
From:   Pratyush Yadav <ptyadav@...zon.de>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
CC:     Pratyush Yadav <ptyadav@...zon.de>,
        Kuniyuki Iwashima <kuniyu@...zon.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Norbert Manthey <nmanthey@...zon.de>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH net] net: fix skb leak in __skb_tstamp_tx()

Commit 50749f2dd685 ("tcp/udp: Fix memleaks of sk and zerocopy skbs with
TX timestamp.") added a call to skb_orphan_frags_rx() to fix leaks with
zerocopy skbs. But it ended up adding a leak of its own. When
skb_orphan_frags_rx() fails, the function just returns, leaking the skb
it just cloned. Free it before returning.

This bug was discovered and resolved using Coverity Static Analysis
Security Testing (SAST) by Synopsys, Inc.

Fixes: 50749f2dd685 ("tcp/udp: Fix memleaks of sk and zerocopy skbs with TX timestamp.")
Signed-off-by: Pratyush Yadav <ptyadav@...zon.de>
---

I do not know this code very well, this was caught by our static
analysis tool. I did not try specifically reproducing the leak but I did
do a boot test by adding this patch on 6.4-rc3 and the kernel boots
fine.

 net/core/skbuff.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 515ec5cdc79c..cea28d30abb5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5224,8 +5224,10 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
 	} else {
 		skb = skb_clone(orig_skb, GFP_ATOMIC);

-		if (skb_orphan_frags_rx(skb, GFP_ATOMIC))
+		if (skb_orphan_frags_rx(skb, GFP_ATOMIC)) {
+			kfree_skb(skb);
 			return;
+		}
 	}
 	if (!skb)
 		return;
--
2.39.2