[ Upstream commit 3bcd6c7eaa ]
After rxrpc_unbundle_conn() has removed a connection from a bundle, it
checks to see if there are any conns with available channels and, if not,
removes and attempts to destroy the bundle.
Whilst it does check after grabbing client_bundles_lock that there are no
connections attached, this races with rxrpc_look_up_bundle() retrieving the
bundle, but not attaching a connection for the connection to be attached
later.
There is therefore a window in which the bundle can get destroyed before we
manage to attach a new connection to it.
Fix this by adding an "active" counter to struct rxrpc_bundle:
(1) rxrpc_connect_call() obtains an active count by prepping/looking up a
bundle and ditches it before returning.
(2) If, during rxrpc_connect_call(), a connection is added to the bundle,
this obtains an active count, which is held until the connection is
discarded.
(3) rxrpc_deactivate_bundle() is created to drop an active count on a
bundle and destroy it when the active count reaches 0. The active
count is checked inside client_bundles_lock() to prevent a race with
rxrpc_look_up_bundle().
(4) rxrpc_unbundle_conn() then calls rxrpc_deactivate_bundle().
Fixes: 245500d853 ("rxrpc: Rewrite the client connection manager")
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-15975
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: zdi-disclosures@trendmicro.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
38fe0988bd