ipx: fix locking regression in ipx_sendmsg and ipx_recvmsg
This fixes an old regression introduced by commitb0d0d915
(ipx: remove the BKL). When a recvmsg syscall blocks waiting for new data, no data can be sent on the same socket with sendmsg because ipx_recvmsg() sleeps with the socket locked. This breaks mars-nwe (NetWare emulator): - the ncpserv process reads the request using recvmsg - ncpserv forks and spawns nwconn - ncpserv calls a (blocking) recvmsg and waits for new requests - nwconn deadlocks in sendmsg on the same socket Commitb0d0d915
has simply replaced BKL locking with lock_sock/release_sock. Unlike now, BKL got unlocked while sleeping, so a blocking recvmsg did not block a concurrent sendmsg. Only keep the socket locked while actually working with the socket data and release it prior to calling skb_recv_datagram(). Signed-off-by: Jiri Bohac <jbohac@suse.cz> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: David S. Miller <davem@davemloft.net>
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parent
d3052bb5d3
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@ -1764,6 +1764,7 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
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struct ipxhdr *ipx = NULL;
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struct sk_buff *skb;
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int copied, rc;
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bool locked = true;
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lock_sock(sk);
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/* put the autobinding in */
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@ -1790,6 +1791,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
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if (sock_flag(sk, SOCK_ZAPPED))
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goto out;
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release_sock(sk);
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locked = false;
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skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
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flags & MSG_DONTWAIT, &rc);
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if (!skb) {
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@ -1826,7 +1829,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
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out_free:
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skb_free_datagram(sk, skb);
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out:
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release_sock(sk);
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if (locked)
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release_sock(sk);
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return rc;
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}
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