linux.git/include/linux/ipc_namespace.h, branch v4.14-rc4

ipc: optimize semget/shmget/msgget for lots of keys

2017-09-09T01:26:51+00:00

ipc_findkey() used to scan all objects to look for the wanted key.  This
is slow when using a high number of keys.  This change adds an rhashtable
of kern_ipc_perm objects in ipc_ids, so that one lookup cease to be O(n).

This change gives a 865% improvement of benchmark reaim.jobs_per_min on a
56 threads Intel(R) Xeon(R) CPU E5-2695 v3 @ 2.30GHz with 256G memory [1]

Other (more micro) benchmark results, by the author: On an i5 laptop, the
following loop executed right after a reboot took, without and with this
change:

    for (int i = 0, k=0x424242; i < KEYS; ++i)
        semget(k++, 1, IPC_CREAT | 0600);

                 total       total          max single  max single
   KEYS        without        with        call without   call with

      1            3.5         4.9   Âµs            3.5         4.9
     10            7.6         8.6   Âµs            3.7         4.7
     32           16.2        15.9   Âµs            4.3         5.3
    100           72.9        41.8   Âµs            3.7         4.7
   1000        5,630.0       502.0   Âµs             *           *
  10000    1,340,000.0     7,240.0   Âµs             *           *
  31900   17,600,000.0    22,200.0   Âµs             *           *

 *: unreliable measure: high variance

The duration for a lookup-only usage was obtained by the same loop once
the keys are present:

                 total       total          max single  max single
   KEYS        without        with        call without   call with

      1            2.1         2.5   Âµs            2.1         2.5
     10            4.5         4.8   Âµs            2.2         2.3
     32           13.0        10.8   Âµs            2.3         2.8
    100           82.9        25.1   Âµs             *          2.3
   1000        5,780.0       217.0   Âµs             *           *
  10000    1,470,000.0     2,520.0   Âµs             *           *
  31900   17,400,000.0     7,810.0   Âµs             *           *

Finally, executing each semget() in a new process gave, when still
summing only the durations of these syscalls:

creation:
                 total       total
   KEYS        without        with

      1            3.7         5.0   Âµs
     10           32.9        36.7   Âµs
     32          125.0       109.0   Âµs
    100          523.0       353.0   Âµs
   1000       20,300.0     3,280.0   Âµs
  10000    2,470,000.0    46,700.0   Âµs
  31900   27,800,000.0   219,000.0   Âµs

lookup-only:
                 total       total
   KEYS        without        with

      1            2.5         2.7   Âµs
     10           25.4        24.4   Âµs
     32          106.0        72.6   Âµs
    100          591.0       352.0   Âµs
   1000       22,400.0     2,250.0   Âµs
  10000    2,510,000.0    25,700.0   Âµs
  31900   28,200,000.0   115,000.0   Âµs

[1] http://lkml.kernel.org/r/20170814060507.GE23258@yexl-desktop

Link: http://lkml.kernel.org/r/20170815194954.ck32ta2z35yuzpwp@debix
Signed-off-by: Guillaume Knispel 
Reviewed-by: Marc Pardo 
Cc: Davidlohr Bueso 
Cc: Kees Cook 
Cc: Manfred Spraul 
Cc: Alexey Dobriyan 
Cc: "Eric W. Biederman" 
Cc: "Peter Zijlstra (Intel)" 
Cc: Ingo Molnar 
Cc: Sebastian Andrzej Siewior 
Cc: Serge Hallyn 
Cc: Andrey Vagin 
Cc: Guillaume Knispel 
Cc: Marc Pardo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc: convert ipc_namespace.count from atomic_t to refcount_t

2017-09-09T01:26:51+00:00

refcount_t type and corresponding API should be used instead of atomic_t
when the variable is used as a reference counter.  This allows to avoid
accidental refcounter overflows that might lead to use-after-free
situations.

Link: http://lkml.kernel.org/r/1499417992-3238-2-git-send-email-elena.reshetova@intel.com
Signed-off-by: Elena Reshetova 
Signed-off-by: Hans Liljestrand 
Signed-off-by: Kees Cook 
Signed-off-by: David Windsor 
Cc: Peter Zijlstra 
Cc: Greg Kroah-Hartman 
Cc: "Eric W. Biederman" 
Cc: Ingo Molnar 
Cc: Alexey Dobriyan 
Cc: Serge Hallyn 
Cc: 
Cc: Davidlohr Bueso 
Cc: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

randstruct: Mark various structs for randomization

2017-06-30T19:00:51+00:00

This marks many critical kernel structures for randomization. These are
structures that have been targeted in the past in security exploits, or
contain functions pointers, pointers to function pointer tables, lists,
workqueues, ref-counters, credentials, permissions, or are otherwise
sensitive. This initial list was extracted from Brad Spengler/PaX Team's
code in the last public patch of grsecurity/PaX based on my understanding
of the code. Changes or omissions from the original code are mine and
don't reflect the original grsecurity/PaX code.

Left out of this list is task_struct, which requires special handling
and will be covered in a subsequent patch.

Signed-off-by: Kees Cook

ipcns: Add a limit on the number of ipc namespaces

2016-08-08T19:42:03+00:00

Acked-by: Kees Cook 
Signed-off-by: "Eric W. Biederman"

ipc: delete "nr_ipc_ns"

2016-08-02T23:35:44+00:00

Write-only variable.

Link: http://lkml.kernel.org/r/20160708214356.GA6785@p183.telecom.by
Signed-off-by: Alexey Dobriyan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

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

2014-12-16T23:53:03+00:00

Pull vfs pile #2 from Al Viro:
 "Next pile (and there'll be one or two more).

  The large piece in this one is getting rid of /proc/*/ns/* weirdness;
  among other things, it allows to (finally) make nameidata completely
  opaque outside of fs/namei.c, making for easier further cleanups in
  there"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  coda_venus_readdir(): use file_inode()
  fs/namei.c: fold link_path_walk() call into path_init()
  path_init(): don't bother with LOOKUP_PARENT in argument
  fs/namei.c: new helper (path_cleanup())
  path_init(): store the "base" pointer to file in nameidata itself
  make default ->i_fop have ->open() fail with ENXIO
  make nameidata completely opaque outside of fs/namei.c
  kill proc_ns completely
  take the targets of /proc/*/ns/* symlinks to separate fs
  bury struct proc_ns in fs/proc
  copy address of proc_ns_ops into ns_common
  new helpers: ns_alloc_inum/ns_free_inum
  make proc_ns_operations work with struct ns_common * instead of void *
  switch the rest of proc_ns_operations to working with &...->ns
  netns: switch ->get()/->put()/->install()/->inum() to working with &net->ns
  make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns
  common object embedded into various struct ....ns

ipc/msg: increase MSGMNI, remove scaling

2014-12-13T20:42:52+00:00

SysV can be abused to allocate locked kernel memory.  For most systems, a
small limit doesn't make sense, see the discussion with regards to SHMMAX.

Therefore: increase MSGMNI to the maximum supported.

And: If we ignore the risk of locking too much memory, then an automatic
scaling of MSGMNI doesn't make sense.  Therefore the logic can be removed.

The code preserves auto_msgmni to avoid breaking any user space applications
that expect that the value exists.

Notes:
1) If an administrator must limit the memory allocations, then he can set
MSGMNI as necessary.

Or he can disable sysv entirely (as e.g. done by Android).

2) MSGMAX and MSGMNB are intentionally not increased, as these values are used
to control latency vs. throughput:
If MSGMNB is large, then msgsnd() just returns and more messages can be queued
before a task switch to a task that calls msgrcv() is forced.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul 
Cc: Davidlohr Bueso 
Cc: Rafael Aquini 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

common object embedded into various struct ....ns

2014-12-04T19:31:00+00:00

for now - just move corresponding ->proc_inum instances over there

Acked-by: "Eric W. Biederman" 
Signed-off-by: Al Viro

ipc,mqueue: remove limits for the amount of system-wide queues

2014-02-25T23:25:45+00:00

Commit 93e6f119c0ce ("ipc/mqueue: cleanup definition names and
locations") added global hardcoded limits to the amount of message
queues that can be created.  While these limits are per-namespace,
reality is that it ends up breaking userspace applications.
Historically users have, at least in theory, been able to create up to
INT_MAX queues, and limiting it to just 1024 is way too low and dramatic
for some workloads and use cases.  For instance, Madars reports:

 "This update imposes bad limits on our multi-process application.  As
  our app uses approaches that each process opens its own set of queues
  (usually something about 3-5 queues per process).  In some scenarios
  we might run up to 3000 processes or more (which of-course for linux
  is not a problem).  Thus we might need up to 9000 queues or more.  All
  processes run under one user."

Other affected users can be found in launchpad bug #1155695:
  https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/1155695

Instead of increasing this limit, revert it entirely and fallback to the
original way of dealing queue limits -- where once a user's resource
limit is reached, and all memory is used, new queues cannot be created.

Signed-off-by: Davidlohr Bueso 
Reported-by: Madars Vitolins 
Acked-by: Doug Ledford 
Cc: Manfred Spraul 
Cc: 	[3.5+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc: delete seq_max field in struct ipc_ids

2014-01-28T05:02:40+00:00

This field is only used to reset the ids seq number if it exceeds the
smaller of INT_MAX/SEQ_MULTIPLIER and USHRT_MAX, and can therefore be
moved out of the structure and into its own macro.  Since each
ipc_namespace contains a table of 3 pointers to struct ipc_ids we can
save space in instruction text:

   text    data     bss     dec     hex filename
  56232    2348      24   58604    e4ec ipc/built-in.o
  56216    2348      24   58588    e4dc ipc/built-in.o-after

Signed-off-by: Davidlohr Bueso 
Reviewed-by: Jonathan Gonzalez 
Cc: Aswin Chandramouleeswaran 
Cc: Rik van Riel 
Acked-by: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds