In theory the AFS_VLSF_BACKVOL flag for a server in a vldb entry
would indicate the presence of a backup volume on that server.

In practice however, this flag is never set, and the presence of
a backup volume is implied by the entry having AFS_VLF_BACKEXISTS set,
for the server that hosts the read-write volume (has AFS_VLSF_RWVOL).

Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

Doing faccessat("/afs/some/directory", 0) triggers a BUG in the permissions
check code.

Fix this by just removing the BUG section.  If no permissions are asked
for, just return okay if the file exists.

Also:

 (1) Split up the directory check so that it has separate if-statements
     rather than if-else-if (e.g. checking for MAY_EXEC shouldn't skip the
     check for MAY_READ and MAY_WRITE).

 (2) Check for MAY_CHDIR as MAY_EXEC.

Without the main fix, the following BUG may occur:

 kernel BUG at fs/afs/security.c:386!
 invalid opcode: 0000 [#1] SMP PTI
 ...
 RIP: 0010:afs_permission+0x19d/0x1a0 [kafs]
 ...
 Call Trace:
  ? inode_permission+0xbe/0x180
  ? do_faccessat+0xdc/0x270
  ? do_syscall_64+0x60/0x1f0
  ? entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fixes: 00d3b7a4533e ("[AFS]: Add security support.")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Signed-off-by: David Howells <dhowells@redhat.com>

Some AFS servers refuse to accept unencrypted traffic, so can't be accessed
with kAFS.  Set the AF_RXRPC security level to encrypt client calls to deal
with this.

Note that incoming service calls are set by the remote client and so aren't
affected by this.

This requires an AF_RXRPC patch to pass the value set by setsockopt to calls
begun by the kernel.

Signed-off-by: David Howells <dhowells@redhat.com>

The handling of CB.CallBack messages sent by the fileserver to the client
is broken in that they are currently being processed after the reply has
been transmitted.

This is not what the fileserver expects, however.  It holds up change
visibility until the reply comes so as to maintain cache coherency, and so
expects the client to have to refetch the state on the affected files.

Fix CB.CallBack handling to perform the callback break before sending the
reply.

The fileserver is free to hold up status fetches issued by other threads on
the same client that occur in reponse to the callback until any pending
changes have been committed.

Fixes: d001648ec7cf ("rxrpc: Don't expose skbs to in-kernel users [ver #2]")
Signed-off-by: David Howells <dhowells@redhat.com>

It's possible for an AFS file server to issue a whole-volume notification
that callbacks on all the vnodes in the file have been broken.  This is
done for R/O and backup volumes (which don't have per-file callbacks) and
for things like a volume being taken offline.

Fix callback handling to detect whole-volume notifications, to track it
across operations and to check it during inode validation.

Fixes: c435ee34551e ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>

The code that looks up servers by addresses makes the assumption
that the list of addresses for a server is sorted.  It exits the
loop if it finds that the target address is larger than the
current candidate.  As the list is not currently sorted, this
can lead to a failure to find a matching server, which can cause
callbacks from that server to be ignored.

Remove the early exit case so that the complete list is searched.

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>

If the client cache manager operations that need the server record
(CB.Callback, CB.InitCallBackState, and CB.InitCallBackState3) can't find
the server record, they abort the call from the file server with
RX_CALL_DEAD when they should return okay.

Fixes: c35eccb1f614 ("[AFS]: Implement the CB.InitCallBackState3 operation.")
Signed-off-by: David Howells <dhowells@redhat.com>

Add a tracepoint to record callbacks from servers for which we don't have a
record.

Signed-off-by: David Howells <dhowells@redhat.com>

Fix the handling of the CB.InitCallBackState3 service call to find the
record of a server that we're using by looking it up by the UUID passed as
the parameter rather than by its address (of which it might have many, and
which may change).

Fixes: c35eccb1f614 ("[AFS]: Implement the CB.InitCallBackState3 operation.")
Signed-off-by: David Howells <dhowells@redhat.com>

If a volume location record lists multiple file servers for a volume, then
it's possible that due to a misconfiguration or a changing configuration
that one of the file servers doesn't know about it yet and will abort
VNOVOL.  Currently, the rotation algorithm will stop with EREMOTEIO.

Fix this by moving on to try the next server if VNOVOL is returned.  Once
all the servers have been tried and the record rechecked, the algorithm
will stop with EREMOTEIO or ENOMEDIUM.

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>