Olga Kornievskaia says: "I ran into this oops in the nfsd (below)
(4.10-rc3 kernel). To trigger this I had a client (unsuccessfully) try
to mount the server with krb5 where the server doesn't have the
rpcsec_gss_krb5 module built."

The problem is that rsci.cred is copied from a svc_cred structure that
gss_proxy didn't properly initialize.  Fix that.

[120408.542387] general protection fault: 0000 [#1] SMP
...
[120408.565724] CPU: 0 PID: 3601 Comm: nfsd Not tainted 4.10.0-rc3+ #16
[120408.567037] Hardware name: VMware, Inc. VMware Virtual =
Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015
[120408.569225] task: ffff8800776f95c0 task.stack: ffffc90003d58000
[120408.570483] RIP: 0010:gss_mech_put+0xb/0x20 [auth_rpcgss]
...
[120408.584946]  ? rsc_free+0x55/0x90 [auth_rpcgss]
[120408.585901]  gss_proxy_save_rsc+0xb2/0x2a0 [auth_rpcgss]
[120408.587017]  svcauth_gss_proxy_init+0x3cc/0x520 [auth_rpcgss]
[120408.588257]  ? __enqueue_entity+0x6c/0x70
[120408.589101]  svcauth_gss_accept+0x391/0xb90 [auth_rpcgss]
[120408.590212]  ? try_to_wake_up+0x4a/0x360
[120408.591036]  ? wake_up_process+0x15/0x20
[120408.592093]  ? svc_xprt_do_enqueue+0x12e/0x2d0 [sunrpc]
[120408.593177]  svc_authenticate+0xe1/0x100 [sunrpc]
[120408.594168]  svc_process_common+0x203/0x710 [sunrpc]
[120408.595220]  svc_process+0x105/0x1c0 [sunrpc]
[120408.596278]  nfsd+0xe9/0x160 [nfsd]
[120408.597060]  kthread+0x101/0x140
[120408.597734]  ? nfsd_destroy+0x60/0x60 [nfsd]
[120408.598626]  ? kthread_park+0x90/0x90
[120408.599448]  ret_from_fork+0x22/0x30

Fixes: 1d658336 "SUNRPC: Add RPC based upcall mechanism for RPCGSS auth"
Cc: stable@vger.kernel.org
Cc: Simo Sorce <simo@redhat.com>
Reported-by: NOlga Kornievskaia <kolga@netapp.com>
Tested-by: NOlga Kornievskaia <kolga@netapp.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Current supplementary groups code can massively overallocate memory and
is implemented in a way so that access to individual gid is done via 2D
array.

If number of gids is <= 32, memory allocation is more or less tolerable
(140/148 bytes).  But if it is not, code allocates full page (!)
regardless and, what's even more fun, doesn't reuse small 32-entry
array.

2D array means dependent shifts, loads and LEAs without possibility to
optimize them (gid is never known at compile time).

All of the above is unnecessary.  Switch to the usual
trailing-zero-len-array scheme.  Memory is allocated with
kmalloc/vmalloc() and only as much as needed.  Accesses become simpler
(LEA 8(gi,idx,4) or even without displacement).

Maximum number of gids is 65536 which translates to 256KB+8 bytes.  I
think kernel can handle such allocation.

On my usual desktop system with whole 9 (nine) aux groups, struct
group_info shrinks from 148 bytes to 44 bytes, yay!

Nice side effects:

 - "gi->gid[i]" is shorter than "GROUP_AT(gi, i)", less typing,

 - fix little mess in net/ipv4/ping.c
   should have been using GROUP_AT macro but this point becomes moot,

 - aux group allocation is persistent and should be accounted as such.

Link: http://lkml.kernel.org/r/20160817201927.GA2096@p183.telecom.bySigned-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Cc: Vasily Kulikov <segoon@openwall.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In an environment where the KDC is running Active Directory, the
exported composite name field returned in the context could be large
enough to span a page boundary.  Attaching a scratch buffer to the
decoding xdr_stream helps deal with those cases.

The case where we saw this was actually due to behavior that's been
fixed in newer gss-proxy versions, but we're fixing it here too.
Signed-off-by: NScott Mayhew <smayhew@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: NSimo Sorce <simo@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Reported-by: NAndi Kleen <andi@firstfloor.org>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

The reply to a gssproxy can include up to NGROUPS_MAX gid's, which will
take up more than a page.  We therefore need to allocate an array of
pages to hold the reply instead of trying to allocate a single huge
buffer.
Tested-by: NSimo Sorce <simo@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

The encoding of linux creds is a bit confusing.

Also: I think in practice it doesn't really matter whether we treat any
of these things as signed or unsigned, but unsigned seems more
straightforward: uid_t/gid_t are unsigned and it simplifies the ngroups
overflow check.
Tested-by: NSimo Sorce <simo@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

We can use the normal coding infrastructure here.

Two minor behavior changes:

	- we're assuming no wasted space at the end of the linux cred.
	  That seems to match gss-proxy's behavior, and I can't see why
	  it would need to do differently in the future.

	- NGROUPS_MAX check added: note groups_alloc doesn't do this,
	  this is the caller's responsibility.
Tested-by: NSimo Sorce <simo@redhat.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Uninitialized stack data was being used as the destination for memcpy's.

Longer term we'll just delete some of this code; all we're doing is
skipping over xdr that we don't care about.

Cc: stable@vger.kernel.org
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

The current code works, but sort of by accident: it obviously didn't
intend the error return to be interpreted as "true".
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

net/sunrpc/auth_gss/gss_rpc_xdr.c: In function ‘gssx_dec_option_array’:
net/sunrpc/auth_gss/gss_rpc_xdr.c:258: warning: ‘creds’ may be used uninitialized in this function

Return early if count is zero, to make it clearer to the compiler (and the
casual reviewer) that no more processing is done.
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

This patch implements a sunrpc client to use the services of the gssproxy
userspace daemon.

In particular it allows to perform calls in user space using an RPC
call instead of custom hand-coded upcall/downcall messages.

Currently only accept_sec_context is implemented as that is all is needed for
the server case.

File server modules like NFS and CIFS can use full gssapi services this way,
once init_sec_context is also implemented.

For the NFS server case this code allow to lift the limit of max 2k krb5
tickets. This limit is prevents legitimate kerberos deployments from using krb5
authentication with the Linux NFS server as they have normally ticket that are
many kilobytes large.

It will also allow to lift the limitation on the size of the credential set
(uid,gid,gids) passed down from user space for users that have very many groups
associated. Currently the downcall mechanism used by rpc.svcgssd is limited
to around 2k secondary groups of the 65k allowed by kernel structures.
Signed-off-by: NSimo Sorce <simo@redhat.com>
[bfields: containerization, concurrent upcalls, misc. fixes and cleanup]
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>