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phonet/pep: fix racy skb_queue_empty() use

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The receive queues are protected by their respective spin-lock, not
the socket lock. This could lead to skb_peek() unexpectedly
returning NULL or a pointer to an already dequeued socket buffer.

Fixes: 9641458d3ec4 ("Phonet: Pipe End Point for Phonet Pipes protocol")
Signed-off-by: Rémi Denis-Courmont <courmisch@gmail.com>
Link: https://lore.kernel.org/r/20240218081214.4806-2-remi@remlab.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Rémi Denis-Courmont 2024-02-18 10:12:14 +02:00 committed by Paolo Abeni
parent 3b2d9bc4d4
commit 7d2a894d7f
1 changed files with 32 additions and 9 deletions
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41
net/phonet/pep.c
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@ -917,6 +917,37 @@ static int pep_sock_enable(struct sock *sk, struct sockaddr *addr, int len)
return 0;
}
static unsigned int pep_first_packet_length(struct sock *sk)
{
struct pep_sock *pn = pep_sk(sk);
struct sk_buff_head *q;
struct sk_buff *skb;
unsigned int len = 0;
bool found = false;
if (sock_flag(sk, SOCK_URGINLINE)) {
q = &pn->ctrlreq_queue;
spin_lock_bh(&q->lock);
skb = skb_peek(q);
if (skb) {
len = skb->len;
found = true;
}
spin_unlock_bh(&q->lock);
}
if (likely(!found)) {
q = &sk->sk_receive_queue;
spin_lock_bh(&q->lock);
skb = skb_peek(q);
if (skb)
len = skb->len;
spin_unlock_bh(&q->lock);
}
return len;
}
static int pep_ioctl(struct sock *sk, int cmd, int *karg)
{
struct pep_sock *pn = pep_sk(sk);
@ -929,15 +960,7 @@ static int pep_ioctl(struct sock *sk, int cmd, int *karg)
break;
}
lock_sock(sk);
if (sock_flag(sk, SOCK_URGINLINE) &&
!skb_queue_empty(&pn->ctrlreq_queue))
*karg = skb_peek(&pn->ctrlreq_queue)->len;
else if (!skb_queue_empty(&sk->sk_receive_queue))
*karg = skb_peek(&sk->sk_receive_queue)->len;
else
*karg = 0;
release_sock(sk);
*karg = pep_first_packet_length(sk);
ret = 0;
break;