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netlink: handle errors from netlink_dump() 

netlink_dump() may failed, but nobody handle its error.
It generates output data, when a previous portion has been returned to
user space. This mechanism works when all data isn't go in skb. If we
enter in netlink_recvmsg() and skb is absent in the recv queue, the
netlink_dump() will not been executed. So if netlink_dump() is failed
one time, the new data never appear and the reader will sleep forever.

netlink_dump() is called from two places:

1. from netlink_sendmsg->...->netlink_dump_start().
   In this place we can report error directly and it will be returned
   by sendmsg().

2. from netlink_recvmsg
   There we can't report error directly, because we have a portion of
   valid output data and call netlink_dump() for prepare the next portion.
   If netlink_dump() is failed, the socket will be mark as error and the
   next recvmsg will be failed.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Andrey Vagin 2011-02-21 02:40:47 +00:00 committed by David S. Miller
parent dad3d44dcb
commit b44d211e16
1 changed files with 14 additions and 4 deletions
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18
net/netlink/af_netlink.c
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@ -1407,7 +1407,7 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
int noblock = flags&MSG_DONTWAIT;
size_t copied;
struct sk_buff *skb, *data_skb;
int err;
int err, ret;
if (flags&MSG_OOB)
return -EOPNOTSUPP;
@ -1470,8 +1470,13 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
skb_free_datagram(sk, skb);
if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2)
netlink_dump(sk);
if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
ret = netlink_dump(sk);
if (ret) {
sk->sk_err = ret;
sk->sk_error_report(sk);
}
}
scm_recv(sock, msg, siocb->scm, flags);
out:
@ -1736,6 +1741,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
struct netlink_callback *cb;
struct sock *sk;
struct netlink_sock *nlk;
int ret;
cb = kzalloc(sizeof(*cb), GFP_KERNEL);
if (cb == NULL)
@ -1764,9 +1770,13 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
nlk->cb = cb;
mutex_unlock(nlk->cb_mutex);
netlink_dump(sk);
ret = netlink_dump(sk);
sock_put(sk);
if (ret)
return ret;
/* We successfully started a dump, by returning -EINTR we
* signal not to send ACK even if it was requested.
*/