diff options
| author | Jiri Bohac <jbohac@suse.cz> | 2014-11-19 23:05:49 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-11-20 22:57:03 -0500 |
| commit | 01462405f0c093b2f8dfddafcadcda6c9e4c5cdf (patch) | |
| tree | b405f0cb9c2f653335ef88507f8ba6d16600c87a /net/ipx | |
| parent | d3052bb5d306b29c1e7d9e5998c5ac4ca1ff0ca9 (diff) | |
| download | lwn-01462405f0c093b2f8dfddafcadcda6c9e4c5cdf.tar.gz lwn-01462405f0c093b2f8dfddafcadcda6c9e4c5cdf.zip | |
ipx: fix locking regression in ipx_sendmsg and ipx_recvmsg
This fixes an old regression introduced by commit
b0d0d915 (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
Commit b0d0d915 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>
Diffstat (limited to 'net/ipx')
| -rw-r--r-- | net/ipx/af_ipx.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c index 91729b807c7d..1b095ca37aa4 100644 --- a/net/ipx/af_ipx.c +++ b/net/ipx/af_ipx.c @@ -1764,6 +1764,7 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock, struct ipxhdr *ipx = NULL; struct sk_buff *skb; int copied, rc; + bool locked = true; lock_sock(sk); /* put the autobinding in */ @@ -1790,6 +1791,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock, if (sock_flag(sk, SOCK_ZAPPED)) goto out; + release_sock(sk); + locked = false; skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT, flags & MSG_DONTWAIT, &rc); if (!skb) { @@ -1826,7 +1829,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock, out_free: skb_free_datagram(sk, skb); out: - release_sock(sk); + if (locked) + release_sock(sk); return rc; } |