linux-kernel - Re: kernel BUG at net/rxrpc/local

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Message-ID: <21982.1566202980@warthog.procyon.org.uk>
Date:   Mon, 19 Aug 2019 09:23:00 +0100
From:   David Howells <dhowells@...hat.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     dhowells@...hat.com,
        syzbot <syzbot+1e0edc4b8b7494c28450@...kaller.appspotmail.com>,
        davem@...emloft.net, dvyukov@...gle.com, ebiggers@...nel.org,
        linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: kernel BUG at net/rxrpc/local_object.c:LINE!

Hi Hillf,

There are some commits in net/master that ought to fix this and conflict with
your longer patch:

	730c5fd42c1e3652a065448fd235cb9fafb2bd10
	rxrpc: Fix local endpoint refcounting

	68553f1a6f746bf860bce3eb42d78c26a717d9c0
	rxrpc: Fix local refcounting

	b00df840fb4004b7087940ac5f68801562d0d2de
	rxrpc: Fix local endpoint replacement

	06d9532fa6b34f12a6d75711162d47c17c1add72
	rxrpc: Fix read-after-free in rxrpc_queue_local()

After the first one, you should never see local->usage == 0 in
rxrpc_input_packet() as the UDP socket gets closed before the refcount is
reduced to 0 (there's now a second "usage" count that counts how many times
the local endpoint is in use and local->usage is the refcount for the struct
itself).

Thanks,
David