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David Howells
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.