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Message-ID: <20231204065952.GA16224@ubuntu>
Date: Sun, 3 Dec 2023 22:59:52 -0800
From: Hyunwoo Kim <v4bel@...ori.io>
To: courmisch@...il.com
Cc: v4bel@...ori.io, imv4bel@...il.com, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
netdev@...r.kernel.org
Subject: [PATCH] net: phonet: Fix Use-After-Free in pep_recvmsg
Because pep_recvmsg() fetches the skb from pn->ctrlreq_queue
without holding the lock_sock and then frees it,
a race can occur with pep_ioctl().
A use-after-free for a skb occurs with the following flow.
```
pep_recvmsg() -> skb_dequeue() -> skb_free_datagram()
pep_ioctl() -> skb_peek()
```
Fix this by adjusting the scope of lock_sock in pep_recvmsg().
Signed-off-by: Hyunwoo Kim <v4bel@...ori.io>
---
net/phonet/pep.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/net/phonet/pep.c b/net/phonet/pep.c
index faba31f2eff2..212d8a9ddaee 100644
--- a/net/phonet/pep.c
+++ b/net/phonet/pep.c
@@ -1250,12 +1250,17 @@ static int pep_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
if (unlikely(1 << sk->sk_state & (TCPF_LISTEN | TCPF_CLOSE)))
return -ENOTCONN;
+ lock_sock(sk);
+
if ((flags & MSG_OOB) || sock_flag(sk, SOCK_URGINLINE)) {
/* Dequeue and acknowledge control request */
struct pep_sock *pn = pep_sk(sk);
- if (flags & MSG_PEEK)
+ if (flags & MSG_PEEK) {
+ release_sock(sk);
return -EOPNOTSUPP;
+ }
+
skb = skb_dequeue(&pn->ctrlreq_queue);
if (skb) {
pep_ctrlreq_error(sk, skb, PN_PIPE_NO_ERROR,
@@ -1263,12 +1268,14 @@ static int pep_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
msg->msg_flags |= MSG_OOB;
goto copy;
}
- if (flags & MSG_OOB)
+
+ if (flags & MSG_OOB) {
+ release_sock(sk);
return -EINVAL;
+ }
}
skb = skb_recv_datagram(sk, flags, &err);
- lock_sock(sk);
if (skb == NULL) {
if (err == -ENOTCONN && sk->sk_state == TCP_CLOSE_WAIT)
err = -ECONNRESET;
@@ -1278,7 +1285,7 @@ static int pep_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
if (sk->sk_state == TCP_ESTABLISHED)
pipe_grant_credits(sk, GFP_KERNEL);
- release_sock(sk);
+
copy:
msg->msg_flags |= MSG_EOR;
if (skb->len > len)
@@ -1291,6 +1298,8 @@ static int pep_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
err = (flags & MSG_TRUNC) ? skb->len : len;
skb_free_datagram(sk, skb);
+
+ release_sock(sk);
return err;
}
--
2.25.1
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