rxrpc: Implement an in-kernel rxperf server for testing purposes

Implement an in-kernel rxperf server to allow kernel-based rxrpc services
to be tested directly, unlike with AFS where they're accessed by the
fileserver when the latter decides it wants to.

This is implemented as a module that, if loaded, opens UDP port 7009
(afs3-rmtsys) and listens on it for incoming calls. Calls can be generated
using the rxperf command shipped with OpenAFS, for example.

Changes
=======
ver #2)
- Use min_t() instead of min().

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: Jakub Kicinski <kuba@kernel.org>

rxrpc: fix some null-ptr-deref bugs in server_key.c

Some function calls are not implemented in rxrpc_no_security, there are
preparse_server_key, free_preparse_server_key and destroy_server_key.
When rxrpc security type is rxrpc_no_security, user can easily trigger a
null-ptr-deref bug via ioctl. So judgment should be added to prevent it

The crash log:
user@syzkaller:~$ ./rxrpc_preparse_s
[ 37.956878][T15626] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 37.957645][T15626] #PF: supervisor instruction fetch in kernel mode
[ 37.958229][T15626] #PF: error_code(0x0010) - not-present page
[ 37.958762][T15626] PGD 4aadf067 P4D 4aadf067 PUD 4aade067 PMD 0
[ 37.959321][T15626] Oops: 0010 [#1] PREEMPT SMP
[ 37.959739][T15626] CPU: 0 PID: 15626 Comm: rxrpc_preparse_ Not tainted 5.17.0-01442-gb47d5a4f6b8d #43
[ 37.960588][T15626] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014
[ 37.961474][T15626] RIP: 0010:0x0
[ 37.961787][T15626] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
[ 37.962480][T15626] RSP: 0018:ffffc9000d9abdc0 EFLAGS: 00010286
[ 37.963018][T15626] RAX: ffffffff84335200 RBX: ffff888012a1ce80 RCX: 0000000000000000
[ 37.963727][T15626] RDX: 0000000000000000 RSI: ffffffff84a736dc RDI: ffffc9000d9abe48
[ 37.964425][T15626] RBP: ffffc9000d9abe48 R08: 0000000000000000 R09: 0000000000000002
[ 37.965118][T15626] R10: 000000000000000a R11: f000000000000000 R12: ffff888013145680
[ 37.965836][T15626] R13: 0000000000000000 R14: ffffffffffffffec R15: ffff8880432aba80
[ 37.966441][T15626] FS: 00007f2177907700(0000) GS:ffff88803ec00000(0000) knlGS:0000000000000000
[ 37.966979][T15626] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 37.967384][T15626] CR2: ffffffffffffffd6 CR3: 000000004aaf1000 CR4: 00000000000006f0
[ 37.967864][T15626] Call Trace:
[ 37.968062][T15626] <TASK>
[ 37.968240][T15626] rxrpc_preparse_s+0x59/0x90
[ 37.968541][T15626] key_create_or_update+0x174/0x510
[ 37.968863][T15626] __x64_sys_add_key+0x139/0x1d0
[ 37.969165][T15626] do_syscall_64+0x35/0xb0
[ 37.969451][T15626] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 37.969824][T15626] RIP: 0033:0x43a1f9

Signed-off-by: Xiaolong Huang <butterflyhuangxx@gmail.com>
Tested-by: Xiaolong Huang <butterflyhuangxx@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: http://lists.infradead.org/pipermail/linux-afs/2022-March/005069.html
Fixes: 12da59fcab5a ("rxrpc: Hand server key parsing off to the security class")
Link: https://lore.kernel.org/r/164865013439.2941502.8966285221215590921.stgit@warthog.procyon.org.uk
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

rxrpc: Allow security classes to give more info on server keys

Allow a security class to give more information on an rxrpc_s-type key when
it is viewed in /proc/keys. This will allow the upcoming RxGK security
class to show the enctype name here.

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

rxrpc: Hand server key parsing off to the security class

Hand responsibility for parsing a server key off to the security class. We
can determine which class from the description. This is necessary as rxgk
server keys have different lookup requirements and different content
requirements (dependent on crypto type) to those of rxkad server keys.

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

rxrpc: Split the server key type (rxrpc_s) into its own file

Split the server private key type (rxrpc_s) out into its own file rather
than mingling it with the authentication/client key type (rxrpc) since they
don't really bear any relation.

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