linux-toradex.git/kernel/cred.c, branch v4.13-rc5

doc: ReSTify credentials.txt

2017-05-18T16:30:19+00:00

This updates the credentials API documentation to ReST markup and moves
it under the security subsection of kernel API documentation.

Cc: David Howells 
Signed-off-by: Kees Cook 
Signed-off-by: Jonathan Corbet

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:28+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

cred: Reject inodes with invalid ids in set_create_file_as()

2016-06-30T23:05:09+00:00

Using INVALID_[UG]ID for the LSM file creation context doesn't
make sense, so return an error if the inode passed to
set_create_file_as() has an invalid id.

Signed-off-by: Seth Forshee 
Acked-by: Serge Hallyn 
Signed-off-by: Eric W. Biederman

kmemcg: account certain kmem allocations to memcg

2016-01-15T00:00:49+00:00

Mark those kmem allocations that are known to be easily triggered from
userspace as __GFP_ACCOUNT/SLAB_ACCOUNT, which makes them accounted to
memcg.  For the list, see below:

 - threadinfo
 - task_struct
 - task_delay_info
 - pid
 - cred
 - mm_struct
 - vm_area_struct and vm_region (nommu)
 - anon_vma and anon_vma_chain
 - signal_struct
 - sighand_struct
 - fs_struct
 - files_struct
 - fdtable and fdtable->full_fds_bits
 - dentry and external_name
 - inode for all filesystems. This is the most tedious part, because
   most filesystems overwrite the alloc_inode method.

The list is far from complete, so feel free to add more objects.
Nevertheless, it should be close to "account everything" approach and
keep most workloads within bounds.  Malevolent users will be able to
breach the limit, but this was possible even with the former "account
everything" approach (simply because it did not account everything in
fact).

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Vladimir Davydov 
Acked-by: Johannes Weiner 
Acked-by: Michal Hocko 
Cc: Tejun Heo 
Cc: Greg Thelen 
Cc: Christoph Lameter 
Cc: Pekka Enberg 
Cc: David Rientjes 
Cc: Joonsoo Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/cred.c: remove unnecessary kdebug atomic reads

2015-09-10T20:29:01+00:00

Commit e0e817392b9a ("CRED: Add some configurable debugging [try #6]")
added the kdebug mechanism to this file back in 2009.

The kdebug macro calls no_printk which always evaluates arguments.

Most of the kdebug uses have an unnecessary call of
	atomic_read(&cred->usage)

Make the kdebug macro do nothing by defining it with
	do { if (0) no_printk(...); } while (0)
when not enabled.

$ size kernel/cred.o* (defconfig x86-64)
   text	   data	    bss	    dec	    hex	filename
   2748	    336	      8	   3092	    c14	kernel/cred.o.new
   2788	    336	      8	   3132	    c3c	kernel/cred.o.old

Miscellanea:
o Neaten the #define kdebug macros while there

Signed-off-by: Joe Perches 
Cc: David Howells 
Cc: James Morris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel: conditionally support non-root users, groups and capabilities

2015-04-15T23:35:22+00:00

There are a lot of embedded systems that run most or all of their
functionality in init, running as root:root.  For these systems,
supporting multiple users is not necessary.

This patch adds a new symbol, CONFIG_MULTIUSER, that makes support for
non-root users, non-root groups, and capabilities optional.  It is enabled
under CONFIG_EXPERT menu.

When this symbol is not defined, UID and GID are zero in any possible case
and processes always have all capabilities.

The following syscalls are compiled out: setuid, setregid, setgid,
setreuid, setresuid, getresuid, setresgid, getresgid, setgroups,
getgroups, setfsuid, setfsgid, capget, capset.

Also, groups.c is compiled out completely.

In kernel/capability.c, capable function was moved in order to avoid
adding two ifdef blocks.

This change saves about 25 KB on a defconfig build.  The most minimal
kernels have total text sizes in the high hundreds of kB rather than
low MB.  (The 25k goes down a bit with allnoconfig, but not that much.

The kernel was booted in Qemu.  All the common functionalities work.
Adding users/groups is not possible, failing with -ENOSYS.

Bloat-o-meter output:
add/remove: 7/87 grow/shrink: 19/397 up/down: 1675/-26325 (-24650)

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Iulia Manda 
Reviewed-by: Josh Triplett 
Acked-by: Geert Uytterhoeven 
Tested-by: Paul E. McKenney 
Reviewed-by: Paul E. McKenney 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2012-12-18T18:55:28+00:00

Pull (again) user namespace infrastructure changes from Eric Biederman:
 "Those bugs, those darn embarrasing bugs just want don't want to get
  fixed.

  Linus I just updated my mirror of your kernel.org tree and it appears
  you successfully pulled everything except the last 4 commits that fix
  those embarrasing bugs.

  When you get a chance can you please repull my branch"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  userns: Fix typo in description of the limitation of userns_install
  userns: Add a more complete capability subset test to commit_creds
  userns: Require CAP_SYS_ADMIN for most uses of setns.
  Fix cap_capable to only allow owners in the parent user namespace to have caps.

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

2012-12-16T23:40:50+00:00

Pull security subsystem updates from James Morris:
 "A quiet cycle for the security subsystem with just a few maintenance
  updates."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  Smack: create a sysfs mount point for smackfs
  Smack: use select not depends in Kconfig
  Yama: remove locking from delete path
  Yama: add RCU to drop read locking
  drivers/char/tpm: remove tasklet and cleanup
  KEYS: Use keyring_alloc() to create special keyrings
  KEYS: Reduce initial permissions on keys
  KEYS: Make the session and process keyrings per-thread
  seccomp: Make syscall skipping and nr changes more consistent
  key: Fix resource leak
  keys: Fix unreachable code
  KEYS: Add payload preparsing opportunity prior to key instantiate or update

userns: Add a more complete capability subset test to commit_creds

2012-12-15T02:36:26+00:00

When unsharing a user namespace we reduce our credentials to just what
can be done in that user namespace.  This is a subset of the credentials
we previously had.  Teach commit_creds to recognize this is a subset
of the credentials we have had before and don't clear the dumpability flag.

This allows an unprivileged  program to do:
unshare(CLONE_NEWUSER);
fd = open("/proc/self/uid_map", O_RDWR);

Where previously opening the uid_map writable would fail because
the the task had been made non-dumpable.

Acked-by: Serge Hallyn 
Signed-off-by: "Eric W. Biederman"

KEYS: Make the session and process keyrings per-thread

2012-10-02T18:24:29+00:00

Make the session keyring per-thread rather than per-process, but still
inherited from the parent thread to solve a problem with PAM and gdm.

The problem is that join_session_keyring() will reject attempts to change the
session keyring of a multithreaded program but gdm is now multithreaded before
it gets to the point of starting PAM and running pam_keyinit to create the
session keyring.  See:

	https://bugs.freedesktop.org/show_bug.cgi?id=49211

The reason that join_session_keyring() will only change the session keyring
under a single-threaded environment is that it's hard to alter the other
thread's credentials to effect the change in a multi-threaded program.  The
problems are such as:

 (1) How to prevent two threads both running join_session_keyring() from
     racing.

 (2) Another thread's credentials may not be modified directly by this process.

 (3) The number of threads is uncertain whilst we're not holding the
     appropriate spinlock, making preallocation slightly tricky.

 (4) We could use TIF_NOTIFY_RESUME and key_replace_session_keyring() to get
     another thread to replace its keyring, but that means preallocating for
     each thread.

A reasonable way around this is to make the session keyring per-thread rather
than per-process and just document that if you want a common session keyring,
you must get it before you spawn any threads - which is the current situation
anyway.

Whilst we're at it, we can the process keyring behave in the same way.  This
means we can clean up some of the ickyness in the creds code.

Basically, after this patch, the session, process and thread keyrings are about
inheritance rules only and not about sharing changes of keyring.

Reported-by: Mantas M. 
Signed-off-by: David Howells 
Tested-by: Ray Strode