linux-toradex.git/security/keys/keyctl.c, branch v3.3.5

Cross Memory Attach

2011-11-01T00:30:44+00:00

The basic idea behind cross memory attach is to allow MPI programs doing
intra-node communication to do a single copy of the message rather than a
double copy of the message via shared memory.

The following patch attempts to achieve this by allowing a destination
process, given an address and size from a source process, to copy memory
directly from the source process into its own address space via a system
call.  There is also a symmetrical ability to copy from the current
process's address space into a destination process's address space.

- Use of /proc/pid/mem has been considered, but there are issues with
  using it:
  - Does not allow for specifying iovecs for both src and dest, assuming
    preadv or pwritev was implemented either the area read from or
  written to would need to be contiguous.
  - Currently mem_read allows only processes who are currently
  ptrace'ing the target and are still able to ptrace the target to read
  from the target. This check could possibly be moved to the open call,
  but its not clear exactly what race this restriction is stopping
  (reason  appears to have been lost)
  - Having to send the fd of /proc/self/mem via SCM_RIGHTS on unix
  domain socket is a bit ugly from a userspace point of view,
  especially when you may have hundreds if not (eventually) thousands
  of processes  that all need to do this with each other
  - Doesn't allow for some future use of the interface we would like to
  consider adding in the future (see below)
  - Interestingly reading from /proc/pid/mem currently actually
  involves two copies! (But this could be fixed pretty easily)

As mentioned previously use of vmsplice instead was considered, but has
problems.  Since you need the reader and writer working co-operatively if
the pipe is not drained then you block.  Which requires some wrapping to
do non blocking on the send side or polling on the receive.  In all to all
communication it requires ordering otherwise you can deadlock.  And in the
example of many MPI tasks writing to one MPI task vmsplice serialises the
copying.

There are some cases of MPI collectives where even a single copy interface
does not get us the performance gain we could.  For example in an
MPI_Reduce rather than copy the data from the source we would like to
instead use it directly in a mathops (say the reduce is doing a sum) as
this would save us doing a copy.  We don't need to keep a copy of the data
from the source.  I haven't implemented this, but I think this interface
could in the future do all this through the use of the flags - eg could
specify the math operation and type and the kernel rather than just
copying the data would apply the specified operation between the source
and destination and store it in the destination.

Although we don't have a "second user" of the interface (though I've had
some nibbles from people who may be interested in using it for intra
process messaging which is not MPI).  This interface is something which
hardware vendors are already doing for their custom drivers to implement
fast local communication.  And so in addition to this being useful for
OpenMPI it would mean the driver maintainers don't have to fix things up
when the mm changes.

There was some discussion about how much faster a true zero copy would
go. Here's a link back to the email with some testing I did on that:

http://marc.info/?l=linux-mm&m=130105930902915&w=2

There is a basic man page for the proposed interface here:

http://ozlabs.org/~cyeoh/cma/process_vm_readv.txt

This has been implemented for x86 and powerpc, other architecture should
mainly (I think) just need to add syscall numbers for the process_vm_readv
and process_vm_writev. There are 32 bit compatibility versions for
64-bit kernels.

For arch maintainers there are some simple tests to be able to quickly
verify that the syscalls are working correctly here:

http://ozlabs.org/~cyeoh/cma/cma-test-20110718.tgz

Signed-off-by: Chris Yeoh 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Thomas Gleixner 
Cc: Arnd Bergmann 
Cc: Paul Mackerras 
Cc: Benjamin Herrenschmidt 
Cc: David Howells 
Cc: James Morris 
Cc: 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

KEYS: Make request_key() and co. return an error for a negative key

2011-03-17T00:59:49+00:00

Make request_key() and co. return an error for a negative or rejected key.  If
the key was simply negated, then return ENOKEY, otherwise return the error
with which it was rejected.

Without this patch, the following command returns a key number (with the latest
keyutils):

	[root@andromeda ~]# keyctl request2 user debug:foo rejected @s
	586569904

Trying to print the key merely gets you a permission denied error:

	[root@andromeda ~]# keyctl print 586569904
	keyctl_read_alloc: Permission denied

Doing another request_key() call does get you the error, as long as it hasn't
expired yet:

	[root@andromeda ~]# keyctl request user debug:foo
	request_key: Key was rejected by service

Signed-off-by: David Howells 
Signed-off-by: James Morris

KEYS: Add an iovec version of KEYCTL_INSTANTIATE

2011-03-08T00:17:22+00:00

Add a keyctl op (KEYCTL_INSTANTIATE_IOV) that is like KEYCTL_INSTANTIATE, but
takes an iovec array and concatenates the data in-kernel into one buffer.
Since the KEYCTL_INSTANTIATE copies the data anyway, this isn't too much of a
problem.

Signed-off-by: David Howells 
Signed-off-by: James Morris

KEYS: Add a new keyctl op to reject a key with a specified error code

2011-03-08T00:17:18+00:00

Add a new keyctl op to reject a key with a specified error code.  This works
much the same as negating a key, and so keyctl_negate_key() is made a special
case of keyctl_reject_key().  The difference is that keyctl_negate_key()
selects ENOKEY as the error to be reported.

Typically the key would be rejected with EKEYEXPIRED, EKEYREVOKED or
EKEYREJECTED, but this is not mandatory.

Signed-off-by: David Howells 
Signed-off-by: James Morris

KEYS: Fix up comments in key management code

2011-01-21T22:59:30+00:00

Fix up comments in the key management code.  No functional changes.

Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

KEYS: Do some style cleanup in the key management code.

2011-01-21T22:59:29+00:00

Do a bit of a style clean up in the key management code.  No functional
changes.

Done using:

  perl -p -i -e 's!^/[*]*/\n!!' security/keys/*.c
  perl -p -i -e 's!} /[*] end [a-z0-9_]*[(][)] [*]/\n!}\n!' security/keys/*.c
  sed -i -s -e ": next" -e N -e 's/^\n[}]$/}/' -e t -e P -e 's/^.*\n//' -e "b next" security/keys/*.c

To remove /*****/ lines, remove comments on the closing brace of a
function to name the function and remove blank lines before the closing
brace of a function.

Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

KEYS: Fix bug in keyctl_session_to_parent() if parent has no session keyring

2010-09-10T14:30:00+00:00

Fix a bug in keyctl_session_to_parent() whereby it tries to check the ownership
of the parent process's session keyring whether or not the parent has a session
keyring [CVE-2010-2960].

This results in the following oops:

  BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
  IP: [] keyctl_session_to_parent+0x251/0x443
  ...
  Call Trace:
   [] ? keyctl_session_to_parent+0x67/0x443
   [] ? __do_fault+0x24b/0x3d0
   [] sys_keyctl+0xb4/0xb8
   [] system_call_fastpath+0x16/0x1b

if the parent process has no session keyring.

If the system is using pam_keyinit then it mostly protected against this as all
processes derived from a login will have inherited the session keyring created
by pam_keyinit during the log in procedure.

To test this, pam_keyinit calls need to be commented out in /etc/pam.d/.

Reported-by: Tavis Ormandy 
Signed-off-by: David Howells 
Acked-by: Tavis Ormandy 
Signed-off-by: Linus Torvalds

KEYS: Fix RCU no-lock warning in keyctl_session_to_parent()

2010-09-10T14:30:00+00:00

There's an protected access to the parent process's credentials in the middle
of keyctl_session_to_parent().  This results in the following RCU warning:

  ===================================================
  [ INFO: suspicious rcu_dereference_check() usage. ]
  ---------------------------------------------------
  security/keys/keyctl.c:1291 invoked rcu_dereference_check() without protection!

  other info that might help us debug this:

  rcu_scheduler_active = 1, debug_locks = 0
  1 lock held by keyctl-session-/2137:
   #0:  (tasklist_lock){.+.+..}, at: [] keyctl_session_to_parent+0x60/0x236

  stack backtrace:
  Pid: 2137, comm: keyctl-session- Not tainted 2.6.36-rc2-cachefs+ #1
  Call Trace:
   [] lockdep_rcu_dereference+0xaa/0xb3
   [] keyctl_session_to_parent+0xed/0x236
   [] sys_keyctl+0xb4/0xb6
   [] system_call_fastpath+0x16/0x1b

The code should take the RCU read lock to make sure the parents credentials
don't go away, even though it's holding a spinlock and has IRQ disabled.

Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

KEYS: Use the variable 'key' in keyctl_describe_key()

2010-08-02T05:34:56+00:00

keyctl_describe_key() turns the key reference it gets into a usable key pointer
and assigns that to a variable called 'key', which it then ignores in favour of
recomputing the key pointer each time it needs it.  Make it use the precomputed
pointer instead.

Without this patch, gcc 4.6 reports that the variable key is set but not used:

	building with gcc 4.6 I'm getting a warning message:
	 CC      security/keys/keyctl.o
	security/keys/keyctl.c: In function 'keyctl_describe_key':
	security/keys/keyctl.c:472:14: warning: variable 'key' set but not used

Reported-by: Justin P. Mattock 
Signed-off-by: David Howells 
Signed-off-by: James Morris

KEYS: Authorise keyctl_set_timeout() on a key if we have its authorisation key

2010-08-02T05:34:27+00:00

Authorise a process to perform keyctl_set_timeout() on an uninstantiated key if
that process has the authorisation key for it.

This allows the instantiator to set the timeout on a key it is instantiating -
provided it does it before instantiating the key.

For instance, the test upcall script provided with the keyutils package could
be modified to set the expiry to an hour hence before instantiating the key:

	[/usr/share/keyutils/request-key-debug.sh]
	 if [ "$3" != "neg" ]
	 then
	+    keyctl timeout $1 3600
	     keyctl instantiate $1 "Debug $3" $4 || exit 1
	 else

Signed-off-by: David Howells 
Signed-off-by: James Morris