Re: [PATCH_V7 0/12] NFSv4 find client fix Version 7

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, Jan 04, 2011 at 03:42:34PM -0500, andros@netapp.com wrote:
> 
> 
> Version 7 of these patches
> Applies to Tronds nfs-for-next branch
> 
> Already acked by bfields
> ------------------------
> 0001-SUNRPC-move-svc_drop-to-caller-of-svc_process_common.patch
> 0002-SUNRPC-fix-bc_send-print.patch
> 0010-NFS-RPC_AUTH_GSS-unsupported-on-v4.1-back-channel.patch
> 0012-NFS-rename-client-back-channel-transport-field.patch

In future, if you don't mind actually adding the "Acked-by"'s to those
patches with your signed-off-by's, that'll help remind me which ones
I've read before as I'm looking through them....

(Well, unless you've changed them in some non-trivial way and want me to
reread them.)

--b.

> 
> Responded to Version 6 comments from bfields.
> ---------------------------------------------
> 0003-SUNRPC-new-transport-for-the-NFSv4.1-shared-back-cha.patch
> 0004-NFS-register-and-unregister-back-channel-transport.patch
> 
> Unchanged:
> ----------
> 0005-NFS-use-svc_create_xprt-for-NFSv4.1-callback-service.patch
> 0006-NFS-do-not-clear-minor-version-at-nfs_client-free.patch
> 0007-NFS-implement-v4.0-callback_ident.patch
> 0008-NFS-associate-sessionid-with-callback-connection.patch
> 0009-NFS-refactor-nfs_find_client-and-reference-client-ac.patch
> 0011-NFS-add-session-back-channel-draining.patch
> 
> 
> The back channel server svc_process_common RPC layer pg_authenticate call
> [nfs_callback_authenticate] is shared by both the NFSv4.0 and the NFSv4.1
> callback threads. It authenticates the incoming request by finding (and
> referencing) an nfs_client struct based on the incoming request address
> and the NFS version (4). This is akin to the NFS server which authenticates
> requests by matching the server address to the exports file client list.
> 
> Since there is no minorversion in the search, it may find the wrong
> nfs_client struct. For the nfsv4.0 callback service thread, this means it
> could find an NFSv4.1 nfs_client. For the NFSv4.1 callback service thread, it
> could find an NFSv4.0 instead of v4.1, or find an NFSv4.1 nfs_client with the
> wrong session.
> 
> The nfs_client is dereferenced at the end of pg_authenticate. Another
> nfs_find_client call is done in the NFS layouer per operation dispatcher
> routines for NFSv4.0 and in the cb_sequence operation dispatcher routine for
> NFSv4.1 after decoding.
> 
> This means the callback server could start processing a callback, passing
> the pg_authenticate test, and have the nfs_client struct freed between the
> pg_authenticate call and the dispatcher operation call. Or, it could have
> found the wrong nfs_client in the pg_authenticate call.
> 
> The current code has this behavior: If the nfs_client is not found in
> pg_authenticate, the request is simply dropped (SVC_DROP). If an nfs_client
> is not found in the dispatcher routines NFS4ERR_BADSESSION is returned for
> v4.1 requests and NFS4ERR_BADHANDLE for v4.0 requests.
> 
> The fix is to implement the v4.0 SETCLIENTID callback_ident and use it to find
> the one and only client for v4.0 callbacks, and to associate the sessionid
> with the sessions based callback service (v4.1) and use it to identify the
> one and only client. This can be done in the NFS layer, in CB_COMPOUND header
> processing for v4.0 and in CB_SEQUENCE processing in v4.1.
> In both cases, a reference to the found client is held across CB_COMPOUND
> processing.
> 
> The pg_authenticate method does not have the callback_ident for CB_NULL or
> CB_COMPOUND v4.0 processing, so just the server address, nfsversion and
> minorversion is used for the client search
> 
> For sessions based callback service, the sessionID can't be set until the
> return of the CREATE_SESSION call, yet the CB_NULL ping from a server can
> be initiated by the server at the receipt of the CREATE_SESSION call before
> the response is sent. So for CB_NULL, the sessionid is (usually) not set, and
> the sessionid is not used for CB_NULL pg_authenticate client searches.
> 
> -->Andy
> 
> --
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