diff options
authorJiri Bohac <jbohac@suse.cz>2014-11-19 23:05:49 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-12-06 15:05:47 -0800
commit3e5b12de56d8fae345d3b331a14bc06f7609a992 (patch)
parentf0eed5a220e777b9e01b9eb45d7e387a35f1f6fa (diff)
ipx: fix locking regression in ipx_sendmsg and ipx_recvmsg
[ Upstream commit 01462405f0c093b2f8dfddafcadcda6c9e4c5cdf ] 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c
index e0897377b3b4..2665bf4b8d05 100644
--- a/net/ipx/af_ipx.c
+++ b/net/ipx/af_ipx.c
@@ -1778,6 +1778,7 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
struct ipxhdr *ipx = NULL;
struct sk_buff *skb;
int copied, rc;
+ bool locked = true;
/* put the autobinding in */
@@ -1804,6 +1805,8 @@ 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)
@@ -1837,7 +1840,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
skb_free_datagram(sk, skb);
- release_sock(sk);
+ if (locked)
+ release_sock(sk);
return rc;