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net: let skb_orphan_partial wake-up waiters.

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Currently the mentioned helper can end-up freeing the socket wmem
without waking-up any processes waiting for more write memory.

If the partially orphaned skb is attached to an UDP (or raw) socket,
the lack of wake-up can hang the user-space.

Even for TCP sockets not calling the sk destructor could have bad
effects on TSQ.

Address the issue using skb_orphan to release the sk wmem before
setting the new sock_efree destructor. Additionally bundle the
whole ownership update in a new helper, so that later other
potential users could avoid duplicate code.

v1 -> v2:
 - use skb_orphan() instead of sort of open coding it (Eric)
 - provide an helper for the ownership change (Eric)

Fixes: f6ba8d33cf ("netem: fix skb_orphan_partial()")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2021-03-30 18:43:54 +02:00 committed by David S. Miller
parent ae81feb733
commit 9adc89af72
2 changed files with 12 additions and 9 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

9
include/net/sock.h
View file

@ -2221,6 +2221,15 @@ static inline void skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
sk_mem_charge(sk, skb->truesize);
}
static inline void skb_set_owner_sk_safe(struct sk_buff *skb, struct sock *sk)
{
if (sk && refcount_inc_not_zero(&sk->sk_refcnt)) {
skb_orphan(skb);
skb->destructor = sock_efree;
skb->sk = sk;
}
}
void sk_reset_timer(struct sock *sk, struct timer_list *timer,
unsigned long expires);

12
net/core/sock.c
View file

@ -2132,16 +2132,10 @@ void skb_orphan_partial(struct sk_buff *skb)
if (skb_is_tcp_pure_ack(skb))
return;
if (can_skb_orphan_partial(skb)) {
struct sock *sk = skb->sk;
if (refcount_inc_not_zero(&sk->sk_refcnt)) {
WARN_ON(refcount_sub_and_test(skb->truesize, &sk->sk_wmem_alloc));
skb->destructor = sock_efree;
}
} else {
if (can_skb_orphan_partial(skb))
skb_set_owner_sk_safe(skb, skb->sk);
else
skb_orphan(skb);
}
}
EXPORT_SYMBOL(skb_orphan_partial);