The patch titled
knfsd: fix race that can disable NFS server
has been removed from the -mm tree. Its filename was
knfsd-fix-race-that-can-disable-nfs-server.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: knfsd: fix race that can disable NFS server
From: NeilBrown <neilb@xxxxxxx>
This patch is suitable for just about any 2.6 kernel. It should go in
2.6.19 and 2.6.18.2 and possible even the .17 and .16 stable series.
This is a long standing bug that seems to have only recently become
apparent, presumably due to increasing use of NFS over TCP - many
distros seem to be making it the default.
The SK_CONN bit gets set when a listening socket may be ready
for an accept, just as SK_DATA is set when data may be available.
It is entirely possible for svc_tcp_accept to be called with neither
of these set. It doesn't happen often but there is a small race in
svc_sock_enqueue as SK_CONN and SK_DATA are tested outside the
spin_lock. They could be cleared immediately after the test and
before the lock is gained.
This normally shouldn't be a problem. The sockets are non-blocking so
trying to read() or accept() when ther is nothing to do is not a problem.
However: svc_tcp_recvfrom makes the decision "Should I accept() or
should I read()" based on whether SK_CONN is set or not. This usually
works but is not safe. The decision should be based on whether it is
a TCP_LISTEN socket or a TCP_CONNECTED socket.
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Cc: Adrian Bunk <bunk@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
net/sunrpc/svcsock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN net/sunrpc/svcsock.c~knfsd-fix-race-that-can-disable-nfs-server net/sunrpc/svcsock.c
--- a/net/sunrpc/svcsock.c~knfsd-fix-race-that-can-disable-nfs-server
+++ a/net/sunrpc/svcsock.c
@@ -973,7 +973,7 @@ svc_tcp_recvfrom(struct svc_rqst *rqstp)
return 0;
}
- if (test_bit(SK_CONN, &svsk->sk_flags)) {
+ if (svsk->sk_sk->sk_state == TCP_LISTEN) {
svc_tcp_accept(svsk);
svc_sock_received(svsk);
return 0;
_
Patches currently in -mm which might be from neilb@xxxxxxx are
origin.patch
md-fix-calculation-of-degraded-for-multipath-and-raid10.patch
md-add-another-compat_ioctl-for-md.patch
md-endian-annotation-for-v1-superblock-access.patch
md-endian-annotations-for-the-bitmap-superblock.patch
lockdep-annotate-nfs-nfsd-in-kernel-sockets.patch
lockdep-annotate-nfs-nfsd-in-kernel-sockets-tidy.patch
remove-lock_key-approach-to-managing-nested-bd_mutex-locks.patch
simplify-some-aspects-of-bd_mutex-nesting.patch
use-mutex_lock_nested-for-bd_mutex-to-avoid-lockdep-warning.patch
avoid-lockdep-warning-in-md.patch
lockdep-annotate-nfsd4-recover-code.patch
md-conditionalize-some-code.patch
md-dm-reduce-stack-usage-with-stacked-block-devices.patch
-
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