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af_unix: Don't call skb_get() for OOB skb.

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Since introduced, OOB skb holds an additional reference count with no
special reason and caused many issues.

Also, kfree_skb() and consume_skb() are used to decrement the count,
which is confusing.

Let's drop the unnecessary skb_get() in queue_oob() and corresponding
kfree_skb(), consume_skb(), and skb_unref().

Now unix_sk(sk)->oob_skb is just a pointer to skb in the receive queue,
so special handing is no longer needed in GC.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20240816233921.57800-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2024-08-16 16:39:21 -07:00 committed by Jakub Kicinski
parent 2862c9349d
commit 8594d9b85c
2 changed files with 7 additions and 36 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

27
net/unix/af_unix.c
View file

@ -693,10 +693,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
unix_state_unlock(sk);
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
if (u->oob_skb) {
kfree_skb(u->oob_skb);
u->oob_skb = NULL;
}
u->oob_skb = NULL;
#endif
wake_up_interruptible_all(&u->peer_wait);
@ -2226,13 +2223,9 @@ static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other
}
maybe_add_creds(skb, sock, other);
skb_get(skb);
scm_stat_add(other, skb);
spin_lock(&other->sk_receive_queue.lock);
if (ousk->oob_skb)
consume_skb(ousk->oob_skb);
WRITE_ONCE(ousk->oob_skb, skb);
__skb_queue_tail(&other->sk_receive_queue, skb);
spin_unlock(&other->sk_receive_queue.lock);
@ -2640,8 +2633,6 @@ static int unix_stream_recv_urg(struct unix_stream_read_state *state)
if (!(state->flags & MSG_PEEK))
WRITE_ONCE(u->oob_skb, NULL);
else
skb_get(oob_skb);
spin_unlock(&sk->sk_receive_queue.lock);
unix_state_unlock(sk);
@ -2651,8 +2642,6 @@ static int unix_stream_recv_urg(struct unix_stream_read_state *state)
if (!(state->flags & MSG_PEEK))
UNIXCB(oob_skb).consumed += 1;
consume_skb(oob_skb);
mutex_unlock(&u->iolock);
if (chunk < 0)
@ -2694,12 +2683,10 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
if (copied) {
skb = NULL;
} else if (!(flags & MSG_PEEK)) {
if (sock_flag(sk, SOCK_URGINLINE)) {
WRITE_ONCE(u->oob_skb, NULL);
consume_skb(skb);
} else {
WRITE_ONCE(u->oob_skb, NULL);
if (!sock_flag(sk, SOCK_URGINLINE)) {
__skb_unlink(skb, &sk->sk_receive_queue);
WRITE_ONCE(u->oob_skb, NULL);
unlinked_skb = skb;
skb = skb_peek(&sk->sk_receive_queue);
}
@ -2710,10 +2697,7 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
spin_unlock(&sk->sk_receive_queue.lock);
if (unlinked_skb) {
WARN_ON_ONCE(skb_unref(unlinked_skb));
kfree_skb(unlinked_skb);
}
kfree_skb(unlinked_skb);
}
return skb;
}
@ -2756,7 +2740,6 @@ static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
unix_state_unlock(sk);
if (drop) {
WARN_ON_ONCE(skb_unref(skb));
kfree_skb(skb);
return -EAGAIN;
}

16
net/unix/garbage.c
View file

@ -337,18 +337,6 @@ static bool unix_vertex_dead(struct unix_vertex *vertex)
return true;
}
static void unix_collect_queue(struct unix_sock *u, struct sk_buff_head *hitlist)
{
skb_queue_splice_init(&u->sk.sk_receive_queue, hitlist);
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
if (u->oob_skb) {
WARN_ON_ONCE(skb_unref(u->oob_skb));
u->oob_skb = NULL;
}
#endif
}
static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist)
{
struct unix_vertex *vertex;
@ -371,11 +359,11 @@ static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist
struct sk_buff_head *embryo_queue = &skb->sk->sk_receive_queue;
spin_lock(&embryo_queue->lock);
unix_collect_queue(unix_sk(skb->sk), hitlist);
skb_queue_splice_init(embryo_queue, hitlist);
spin_unlock(&embryo_queue->lock);
}
} else {
unix_collect_queue(u, hitlist);
skb_queue_splice_init(queue, hitlist);
}
spin_unlock(&queue->lock);