tree a4e6c32da8353afe7d4b0ffe49c4c6bb790374c2
parent a05354cbb82248469f907712587992c52fd1c254
author David Howells <dhowells@redhat.com> 1565649006 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1567060139 +0200

rxrpc: Fix local endpoint replacement

[ Upstream commit b00df840fb4004b7087940ac5f68801562d0d2de ]

When a local endpoint (struct rxrpc_local) ceases to be in use by any
AF_RXRPC sockets, it starts the process of being destroyed, but this
doesn't cause it to be removed from the namespace endpoint list immediately
as tearing it down isn't trivial and can't be done in softirq context, so
it gets deferred.

If a new socket comes along that wants to bind to the same endpoint, a new
rxrpc_local object will be allocated and rxrpc_lookup_local() will use
list_replace() to substitute the new one for the old.

Then, when the dying object gets to rxrpc_local_destroyer(), it is removed
unconditionally from whatever list it is on by calling list_del_init().

However, list_replace() doesn't reset the pointers in the replaced
list_head and so the list_del_init() will likely corrupt the local
endpoints list.

Fix this by using list_replace_init() instead.

Fixes: 730c5fd42c1e ("rxrpc: Fix local endpoint refcounting")
Reported-by: syzbot+193e29e9387ea5837f1d@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>