From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
commit 5121197ecc5db58c07da95eb1ff82b98b121a221 upstream.
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: shaozhengchao <shaozhengchao@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Tom Herbert <tom@xxxxxxxxxxxxxxx>
Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221114005119.597905-1-xiyou.wangcong@xxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/kcm/kcmsock.c | 60 +++++++-----------------------------------------------
1 file changed, 8 insertions(+), 52 deletions(-)
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -221,7 +221,7 @@ static void requeue_rx_msgs(struct kcm_m
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);
@@ -1084,53 +1084,18 @@ 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)
{
+ int noblock = flags & MSG_DONTWAIT;
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, noblock, &err);
if (!skb)
goto out;
@@ -1161,14 +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;
}
@@ -1176,9 +1138,9 @@ static ssize_t kcm_splice_read(struct so
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
+ int noblock = flags & MSG_DONTWAIT;
struct sock *sk = sock->sk;
struct kcm_sock *kcm = kcm_sk(sk);
- long timeo;
struct strp_msg *stm;
int err = 0;
ssize_t copied;
@@ -1186,11 +1148,7 @@ static ssize_t kcm_splice_read(struct so
/* 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, noblock, &err);
if (!skb)
goto err_out;
@@ -1218,13 +1176,11 @@ static ssize_t kcm_splice_read(struct so
* 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;
}
