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authorCong Wang <cong.wang@bytedance.com>2022-11-13 16:51:19 -0800
committerPaolo Abeni <pabeni@redhat.com>2022-11-15 12:42:26 +0100
commit5121197ecc5db58c07da95eb1ff82b98b121a221 (patch)
tree88035496d9ecd825ad38a68b7e47a95878058995 /net/kcm
parent280c0f7cd0aa4d190619b18243110e052a90775c (diff)
kcm: close race conditions on sk_receive_queue
sk->sk_receive_queue is protected by skb queue lock, but for KCM sockets its RX path takes mux->rx_lock to protect more than just skb queue. However, kcm_recvmsg() still only grabs the skb queue lock, so race conditions still exist. We can teach kcm_recvmsg() to grab mux->rx_lock too but this would introduce a potential performance regression as struct kcm_mux can be shared by multiple KCM sockets. So we have to enforce skb queue lock in requeue_rx_msgs() and handle skb peek case carefully in kcm_wait_data(). Fortunately, skb_recv_datagram() already handles it nicely and is widely used by other sockets, we can just switch to skb_recv_datagram() after getting rid of the unnecessary sock lock in kcm_recvmsg() and kcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets, so it is safe to get rid of this check too. I ran the original syzbot reproducer for 30 min without seeing any issue. Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Reported-by: syzbot+278279efdd2730dd14bf@syzkaller.appspotmail.com Reported-by: shaozhengchao <shaozhengchao@huawei.com> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Tom Herbert <tom@herbertland.com> Signed-off-by: Cong Wang <cong.wang@bytedance.com> Link: https://lore.kernel.org/r/20221114005119.597905-1-xiyou.wangcong@gmail.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/kcm')
-rw-r--r--net/kcm/kcmsock.c58
1 files changed, 6 insertions, 52 deletions
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index a5004228111d..890a2423f559 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -222,7 +222,7 @@ static void requeue_rx_msgs(struct kcm_mux *mux, struct sk_buff_head *head)
struct sk_buff *skb;
struct kcm_sock *kcm;
- while ((skb = __skb_dequeue(head))) {
+ while ((skb = skb_dequeue(head))) {
/* Reset destructor to avoid calling kcm_rcv_ready */
skb->destructor = sock_rfree;
skb_orphan(skb);
@@ -1085,53 +1085,17 @@ out_error:
return err;
}
-static struct sk_buff *kcm_wait_data(struct sock *sk, int flags,
- long timeo, int *err)
-{
- struct sk_buff *skb;
-
- while (!(skb = skb_peek(&sk->sk_receive_queue))) {
- if (sk->sk_err) {
- *err = sock_error(sk);
- return NULL;
- }
-
- if (sock_flag(sk, SOCK_DONE))
- return NULL;
-
- if ((flags & MSG_DONTWAIT) || !timeo) {
- *err = -EAGAIN;
- return NULL;
- }
-
- sk_wait_data(sk, &timeo, NULL);
-
- /* Handle signals */
- if (signal_pending(current)) {
- *err = sock_intr_errno(timeo);
- return NULL;
- }
- }
-
- return skb;
-}
-
static int kcm_recvmsg(struct socket *sock, struct msghdr *msg,
size_t len, int flags)
{
struct sock *sk = sock->sk;
struct kcm_sock *kcm = kcm_sk(sk);
int err = 0;
- long timeo;
struct strp_msg *stm;
int copied = 0;
struct sk_buff *skb;
- timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
-
- lock_sock(sk);
-
- skb = kcm_wait_data(sk, flags, timeo, &err);
+ skb = skb_recv_datagram(sk, flags, &err);
if (!skb)
goto out;
@@ -1162,14 +1126,11 @@ msg_finished:
/* Finished with message */
msg->msg_flags |= MSG_EOR;
KCM_STATS_INCR(kcm->stats.rx_msgs);
- skb_unlink(skb, &sk->sk_receive_queue);
- kfree_skb(skb);
}
}
out:
- release_sock(sk);
-
+ skb_free_datagram(sk, skb);
return copied ? : err;
}
@@ -1179,7 +1140,6 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos,
{
struct sock *sk = sock->sk;
struct kcm_sock *kcm = kcm_sk(sk);
- long timeo;
struct strp_msg *stm;
int err = 0;
ssize_t copied;
@@ -1187,11 +1147,7 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos,
/* Only support splice for SOCKSEQPACKET */
- timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
-
- lock_sock(sk);
-
- skb = kcm_wait_data(sk, flags, timeo, &err);
+ skb = skb_recv_datagram(sk, flags, &err);
if (!skb)
goto err_out;
@@ -1219,13 +1175,11 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos,
* finish reading the message.
*/
- release_sock(sk);
-
+ skb_free_datagram(sk, skb);
return copied;
err_out:
- release_sock(sk);
-
+ skb_free_datagram(sk, skb);
return err;
}