linux-kernel - [PATCH 5.10 061/167] bpf, sockmap: Fix potential memory leak on unlikely error case

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Message-Id: <20210726153841.453111153@linuxfoundation.org>
Date:   Mon, 26 Jul 2021 17:38:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Cong Wang <cong.wang@...edance.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 061/167] bpf, sockmap: Fix potential memory leak on unlikely error case

From: John Fastabend <john.fastabend@...il.com>

[ Upstream commit 7e6b27a69167f97c56b5437871d29e9722c3e470 ]

If skb_linearize is needed and fails we could leak a msg on the error
handling. To fix ensure we kfree the msg block before returning error.
Found during code review.

Fixes: 4363023d2668e ("bpf, sockmap: Avoid failures from skb_to_sgvec when skb has frag_list")
Signed-off-by: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Cong Wang <cong.wang@...edance.com>
Link: https://lore.kernel.org/bpf/20210712195546.423990-2-john.fastabend@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/core/skmsg.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 923a1d0f84ca..c4c224a5b9de 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -433,10 +433,8 @@ static int sk_psock_skb_ingress_enqueue(struct sk_buff *skb,
 	if (skb_linearize(skb))
 		return -EAGAIN;
 	num_sge = skb_to_sgvec(skb, msg->sg.data, 0, skb->len);
-	if (unlikely(num_sge < 0)) {
-		kfree(msg);
+	if (unlikely(num_sge < 0))
 		return num_sge;
-	}
 
 	copied = skb->len;
 	msg->sg.start = 0;
@@ -455,6 +453,7 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
 {
 	struct sock *sk = psock->sk;
 	struct sk_msg *msg;
+	int err;
 
 	/* If we are receiving on the same sock skb->sk is already assigned,
 	 * skip memory accounting and owner transition seeing it already set
@@ -473,7 +472,10 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
 	 * into user buffers.
 	 */
 	skb_set_owner_r(skb, sk);
-	return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+	err = sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+	if (err < 0)
+		kfree(msg);
+	return err;
 }
 
 /* Puts an skb on the ingress queue of the socket already assigned to the
@@ -484,12 +486,16 @@ static int sk_psock_skb_ingress_self(struct sk_psock *psock, struct sk_buff *skb
 {
 	struct sk_msg *msg = kzalloc(sizeof(*msg), __GFP_NOWARN | GFP_ATOMIC);
 	struct sock *sk = psock->sk;
+	int err;
 
 	if (unlikely(!msg))
 		return -EAGAIN;
 	sk_msg_init(msg);
 	skb_set_owner_r(skb, sk);
-	return sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+	err = sk_psock_skb_ingress_enqueue(skb, psock, sk, msg);
+	if (err < 0)
+		kfree(msg);
+	return err;
 }
 
 static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
-- 
2.30.2