[PATCH net 0/2] rxrpc: Fixes

[PATCH net 0/2] rxrpc: Fixes

[David Howells]

Here are a couple of fixes for rxrpc:

 (1) Fix a potential deadlock in the peer keepalive dispatcher.

 (2) Fix a missing notification when a UDP sendmsg error occurs in rxrpc.


The patches are tagged here:

	git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
	rxrpc-fixes-20190730

and can also be found on the following branch:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=rxrpc-fixes

David
---
David Howells (2):
      rxrpc: Fix potential deadlock
      rxrpc: Fix the lack of notification when sendmsg() fails on a DATA packet


 net/rxrpc/ar-internal.h |    1 +
 net/rxrpc/peer_event.c  |    2 +-
 net/rxrpc/peer_object.c |   18 ++++++++++++++++++
 net/rxrpc/sendmsg.c     |    1 +
 4 files changed, 21 insertions(+), 1 deletion(-)

[PATCH net 1/2] rxrpc: Fix potential deadlock

[David Howells]

There is a potential deadlock in rxrpc_peer_keepalive_dispatch() whereby
rxrpc_put_peer() is called with the peer_hash_lock held, but if it reduces
the peer's refcount to 0, rxrpc_put_peer() calls __rxrpc_put_peer() - which
the tries to take the already held lock.

Fix this by providing a version of rxrpc_put_peer() that can be called in
situations where the lock is already held.

The bug may produce the following lockdep report:

============================================
WARNING: possible recursive locking detected
5.2.0-next-20190718 #41 Not tainted
--------------------------------------------
kworker/0:3/21678 is trying to acquire lock:
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh
/./include/linux/spinlock.h:343 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
__rxrpc_put_peer /net/rxrpc/peer_object.c:415 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
rxrpc_put_peer+0x2d3/0x6a0 /net/rxrpc/peer_object.c:435

but task is already holding lock:
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at: spin_lock_bh
/./include/linux/spinlock.h:343 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
rxrpc_peer_keepalive_dispatch /net/rxrpc/peer_event.c:378 [inline]
00000000aa5eecdf (&(&rxnet->peer_hash_lock)->rlock){+.-.}, at:
rxrpc_peer_keepalive_worker+0x6b3/0xd02 /net/rxrpc/peer_event.c:430

Fixes: 330bdcfadcee ("rxrpc: Fix the keepalive generator [ver #2]")
Reported-by: syzbot+72af434e4b3417318f84@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
---

 net/rxrpc/ar-internal.h |    1 +
 net/rxrpc/peer_event.c  |    2 +-
 net/rxrpc/peer_object.c |   18 ++++++++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 80335b4ee4fd..822f45386e31 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -1061,6 +1061,7 @@ void rxrpc_destroy_all_peers(struct rxrpc_net *);
 struct rxrpc_peer *rxrpc_get_peer(struct rxrpc_peer *);
 struct rxrpc_peer *rxrpc_get_peer_maybe(struct rxrpc_peer *);
 void rxrpc_put_peer(struct rxrpc_peer *);
+void rxrpc_put_peer_locked(struct rxrpc_peer *);
 
 /*
  * proc.c
diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index 9f2f45c09e58..7666ec72d37e 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -378,7 +378,7 @@ static void rxrpc_peer_keepalive_dispatch(struct rxrpc_net *rxnet,
 		spin_lock_bh(&rxnet->peer_hash_lock);
 		list_add_tail(&peer->keepalive_link,
 			      &rxnet->peer_keepalive[slot & mask]);
-		rxrpc_put_peer(peer);
+		rxrpc_put_peer_locked(peer);
 	}
 
 	spin_unlock_bh(&rxnet->peer_hash_lock);
diff --git a/net/rxrpc/peer_object.c b/net/rxrpc/peer_object.c
index 9d3ce81cf8ae..9c3ac96f71cb 100644
--- a/net/rxrpc/peer_object.c
+++ b/net/rxrpc/peer_object.c
@@ -436,6 +436,24 @@ void rxrpc_put_peer(struct rxrpc_peer *peer)
 	}
 }
 
+/*
+ * Drop a ref on a peer record where the caller already holds the
+ * peer_hash_lock.
+ */
+void rxrpc_put_peer_locked(struct rxrpc_peer *peer)
+{
+	const void *here = __builtin_return_address(0);
+	int n;
+
+	n = atomic_dec_return(&peer->usage);
+	trace_rxrpc_peer(peer, rxrpc_peer_put, n, here);
+	if (n == 0) {
+		hash_del_rcu(&peer->hash_link);
+		list_del_init(&peer->keepalive_link);
+		kfree_rcu(peer, rcu);
+	}
+}
+
 /*
  * Make sure all peer records have been discarded.
  */

[PATCH net 2/2] rxrpc: Fix the lack of notification when sendmsg() fails on a DATA packet

[David Howells]

Fix the fact that a notification isn't sent to the recvmsg side to indicate
a call failed when sendmsg() fails to transmit a DATA packet with the error
ENETUNREACH, EHOSTUNREACH or ECONNREFUSED.

Without this notification, the afs client just sits there waiting for the
call to complete in some manner (which it's not now going to do), which
also pins the rxrpc call in place.

This can be seen if the client has a scope-level IPv6 address, but not a
global-level IPv6 address, and we try and transmit an operation to a
server's IPv6 address.

Looking in /proc/net/rxrpc/calls shows completed calls just sat there with
an abort code of RX_USER_ABORT and an error code of -ENETUNREACH.

Fixes: c54e43d752c7 ("rxrpc: Fix missing start of call timeout")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
---

 net/rxrpc/sendmsg.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 5d3f33ce6d41..bae14438f869 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -226,6 +226,7 @@ static int rxrpc_queue_packet(struct rxrpc_sock *rx, struct rxrpc_call *call,
 			rxrpc_set_call_completion(call,
 						  RXRPC_CALL_LOCAL_ERROR,
 						  0, ret);
+			rxrpc_notify_socket(call);
 			goto out;
 		}
 		_debug("need instant resend %d", ret);

Re: [PATCH net 0/2] rxrpc: Fixes

[David Miller]

From: David Howells <dhowells@redhat.com>
Date: Tue, 30 Jul 2019 15:50:11 +0100

> 
> Here are a couple of fixes for rxrpc:
> 
>  (1) Fix a potential deadlock in the peer keepalive dispatcher.
> 
>  (2) Fix a missing notification when a UDP sendmsg error occurs in rxrpc.
> 
> 
> The patches are tagged here:
> 
> 	git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
> 	rxrpc-fixes-20190730

Pulled, thanks David.