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  1. Apr 08, 2014
  3. Apr 04, 2014
    • Johannes Weiner's avatar
      mm + fs: store shadow entries in page cache · 91b0abe3
      Johannes Weiner authored 
      
Reclaim will be leaving shadow entries in the page cache radix tree upon
evicting the real page.  As those pages are found from the LRU, an
iput() can lead to the inode being freed concurrently.  At this point,
reclaim must no longer install shadow pages because the inode freeing
code needs to ensure the page tree is really empty.

Add an address_space flag, AS_EXITING, that the inode freeing code sets
under the tree lock before doing the final truncate.  Reclaim will check
for this flag before installing shadow pages.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Reviewed-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      91b0abe3
  5. Dec 13, 2013
    • Jan Beulich's avatar
      procfs: also fix proc_reg_get_unmapped_area() for !MMU case · ae5758a1
      Jan Beulich authored 
      
Commit fad1a86e ("procfs: call default get_unmapped_area on
MMU-present architectures"), as its title says, took care of only the
MMU case, leaving the !MMU side still in the regressed state (returning
-EIO in all cases where pde->proc_fops->get_unmapped_area is NULL).

From the fad1a86e changelog:

 "Commit c4fe2448 ("sparc: fix PCI device proc file mmap(2)") added
  proc_reg_get_unmapped_area in proc_reg_file_ops and
  proc_reg_file_ops_no_compat, by which now mmap always returns EIO if
  get_unmapped_area method is not defined for the target procfs file, which
  causes regression of mmap on /proc/vmcore.

  To address this issue, like get_unmapped_area(), call default
  current->mm->get_unmapped_area on MMU-present architectures if
  pde->proc_fops->get_unmapped_area, i.e.  the one in actual file operation
  in the procfs file, is not defined"

Signed-off-by: default avatarJan Beulich <jbeulich@suse.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: <stable@vger.kernel.org>	[3.12.x]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ae5758a1
  7. Nov 13, 2013
  9. Oct 17, 2013
  11. Sep 05, 2013
  13. May 01, 2013
  15. Apr 29, 2013
  17. Apr 09, 2013
  19. Mar 22, 2013
    • Linus Torvalds's avatar
      vfs,proc: guarantee unique inodes in /proc · 51f0885e
      Linus Torvalds authored 
      
Dave Jones found another /proc issue with his Trinity tool: thanks to
the namespace model, we can have multiple /proc dentries that point to
the same inode, aliasing directories in /proc/<pid>/net/ for example.

This ends up being a total disaster, because it acts like hardlinked
directories, and causes locking problems.  We rely on the topological
sort of the inodes pointed to by dentries, and if we have aliased
directories, that odering becomes unreliable.

In short: don't do this.  Multiple dentries with the same (directory)
inode is just a bad idea, and the namespace code should never have
exposed things this way.  But we're kind of stuck with it.

This solves things by just always allocating a new inode during /proc
dentry lookup, instead of using "iget_locked()" to look up existing
inodes by superblock and number.  That actually simplies the code a bit,
at the cost of potentially doing more inode [de]allocations.

That said, the inode lookup wasn't free either (and did a lot of locking
of inodes), so it is probably not that noticeable.  We could easily keep
the old lookup model for non-directory entries, but rather than try to
be excessively clever this just implements the minimal and simplest
workaround for the problem.

Reported-and-tested-by: default avatarDave Jones <davej@redhat.com>
Analyzed-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      51f0885e
  21. Feb 28, 2013
  23. Feb 26, 2013
  25. Feb 23, 2013
  27. Nov 20, 2012
  29. Oct 05, 2012
  31. May 15, 2012
  33. May 06, 2012
  35. Mar 28, 2012
  37. Mar 21, 2012
  39. Jan 11, 2012
    • Vasiliy Kulikov's avatar
      procfs: add hidepid= and gid= mount options · 0499680a
      Vasiliy Kulikov authored 
      Add support for mount options to restrict access to /proc/PID/
directories.  The default backward-compatible "relaxed" behaviour is left
untouched.

The first mount option is called "hidepid" and its value defines how much
info about processes we want to be available for non-owners:

hidepid=0 (default) means the old behavior - anybody may read all
world-readable /proc/PID/* files.

hidepid=1 means users may not access any /proc/<pid>/ directories, but
their own.  Sensitive files like cmdline, sched*, status are now protected
against other users.  As permission checking done in proc_pid_permission()
and files' permissions are left untouched, programs expecting specific
files' modes are not confused.

hidepid=2 means hidepid=1 plus all /proc/PID/ will be invisible to other
users.  It doesn't mean that it hides whether a process exists (it can be
learned by other means, e.g.  by kill -0 $PID), but it hides process' euid
and egid.  It compicates intruder's task of gathering info about running
processes, whether some daemon runs with elevated privileges, whether
another user runs some sensitive program, whether other users run any
program at all, etc.

gid=XXX defines a group that will be able to gather all processes' info
(as in hidepid=0 mode).  This group should be used instead of putting
nonroot user in sudoers file or something.  However, untrusted users (like
daemons, etc.) which are not supposed to monitor the tasks in the whole
system should not be added to the group.

hidepid=1 or higher is designed to restrict access to procfs files, which
might reveal some sensitive private information like precise keystrokes
timings:

http://www.openwall.com/lists/oss-security/2011/11/05/3

hidepid=1/2 doesn't break monitoring userspace tools.  ps, top, pgrep, and
conky gracefully handle EPERM/ENOENT and behave as if the current user is
the only user running processes.  pstree shows the process subtree which
contains "pstree" process.

Note: the patch doesn't deal with setuid/setgid issues of keeping
preopened descriptors of procfs files (like
https://lkml.org/lkml/2011/2/7/368

).  We rely on that the leaked
information like the scheduling counters of setuid apps doesn't threaten
anybody's privacy - only the user started the setuid program may read the
counters.

Signed-off-by: default avatarVasiliy Kulikov <segoon@openwall.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <greg@kroah.com>
Cc: Theodore Tso <tytso@MIT.EDU>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: James Morris <jmorris@namei.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0499680a
    • Vasiliy Kulikov's avatar
      procfs: parse mount options · 97412950
      Vasiliy Kulikov authored 
      
Add support for procfs mount options.  Actual mount options are coming in
the next patches.

Signed-off-by: default avatarVasiliy Kulikov <segoon@openwall.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <greg@kroah.com>
Cc: Theodore Tso <tytso@MIT.EDU>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: James Morris <jmorris@namei.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      97412950
  41. Jan 04, 2012
    • Al Viro's avatar
      vfs: fix the stupidity with i_dentry in inode destructors · 6b520e05
      Al Viro authored 
      
Seeing that just about every destructor got that INIT_LIST_HEAD() copied into
it, there is no point whatsoever keeping this INIT_LIST_HEAD in inode_init_once();
the cost of taking it into inode_init_always() will be negligible for pipes
and sockets and negative for everything else.  Not to mention the removal of
boilerplate code from ->destroy_inode() instances...

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      6b520e05
  43. Nov 02, 2011
  45. Jul 27, 2011
  47. May 10, 2011
    • Eric W. Biederman's avatar
      ns: proc files for namespace naming policy. · 6b4e306a
      Eric W. Biederman authored 
      
Create files under /proc/<pid>/ns/ to allow controlling the
namespaces of a process.

This addresses three specific problems that can make namespaces hard to
work with.
- Namespaces require a dedicated process to pin them in memory.
- It is not possible to use a namespace unless you are the child
  of the original creator.
- Namespaces don't have names that userspace can use to talk about
  them.

The namespace files under /proc/<pid>/ns/ can be opened and the
file descriptor can be used to talk about a specific namespace, and
to keep the specified namespace alive.

A namespace can be kept alive by either holding the file descriptor
open or bind mounting the file someplace else.  aka:
mount --bind /proc/self/ns/net /some/filesystem/path
mount --bind /proc/self/fd/<N> /some/filesystem/path

This allows namespaces to be named with userspace policy.

It requires additional support to make use of these filedescriptors
and that will be comming in the following patches.

Acked-by: default avatarDaniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
      6b4e306a
  49. Mar 24, 2011
  51. Mar 08, 2011
    • Al Viro's avatar
      unfuck proc_sysctl ->d_compare() · dfef6dcd
      Al Viro authored 
      
a) struct inode is not going to be freed under ->d_compare();
however, the thing PROC_I(inode)->sysctl points to just might.
Fortunately, it's enough to make freeing that sucker delayed,
provided that we don't step on its ->unregistering, clear
the pointer to it in PROC_I(inode) before dropping the reference
and check if it's NULL in ->d_compare().

b) I'm not sure that we *can* walk into NULL inode here (we recheck
dentry->seq between verifying that it's still hashed / fetching
dentry->d_inode and passing it to ->d_compare() and there's no
negative hashed dentries in /proc/sys/*), but if we can walk into
that, we really should not have ->d_compare() return 0 on it!
Said that, I really suspect that this check can be simply killed.
Nick?

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      dfef6dcd
  53. Jan 13, 2011
  55. Jan 07, 2011
    • Nicholas Piggin's avatar
      fs: icache RCU free inodes · fa0d7e3d
      Nicholas Piggin authored 
      
RCU free the struct inode. This will allow:

- Subsequent store-free path walking patch. The inode must be consulted for
  permissions when walking, so an RCU inode reference is a must.
- sb_inode_list_lock to be moved inside i_lock because sb list walkers who want
  to take i_lock no longer need to take sb_inode_list_lock to walk the list in
  the first place. This will simplify and optimize locking.
- Could remove some nested trylock loops in dcache code
- Could potentially simplify things a bit in VM land. Do not need to take the
  page lock to follow page->mapping.

The downsides of this is the performance cost of using RCU. In a simple
creat/unlink microbenchmark, performance drops by about 10% due to inability to
reuse cache-hot slab objects. As iterations increase and RCU freeing starts
kicking over, this increases to about 20%.

In cases where inode lifetimes are longer (ie. many inodes may be allocated
during the average life span of a single inode), a lot of this cache reuse is
not applicable, so the regression caused by this patch is smaller.

The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU,
however this adds some complexity to list walking and store-free path walking,
so I prefer to implement this at a later date, if it is shown to be a win in
real situations. I haven't found a regression in any non-micro benchmark so I
doubt it will be a problem.

Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
      fa0d7e3d
  57. Nov 17, 2010
  59. Aug 14, 2010
  61. Aug 09, 2010