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authorJiri Bohac <jbohac@suse.cz>2014-11-19 23:05:49 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-12-06 15:55:34 -0800
commit8b25535501e3c9d8403fef20c3c272399394bc4f (patch)
treefe32ce0a34eb19821ebd96856f4d6fc121eee236
parent32b849a714aad7701a1fc53953272b83a6dc483a (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>
-rw-r--r--net/ipx/af_ipx.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c
index 00b2a6d1c009..d65aea21ce81 100644
--- a/net/ipx/af_ipx.c
+++ b/net/ipx/af_ipx.c
@@ -1763,6 +1763,7 @@ 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 */
@@ -1789,6 +1790,8 @@ 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)
@@ -1822,7 +1825,8 @@ 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;
}