linux-stable.git/include/linux/sched.h, branch v3.12.64

pipe: limit the per-user amount of pages allocated in pipes

2016-04-21T11:11:54+00:00

commit 759c01142a5d0f364a462346168a56de28a80f52 upstream.

On no-so-small systems, it is possible for a single process to cause an
OOM condition by filling large pipes with data that are never read. A
typical process filling 4000 pipes with 1 MB of data will use 4 GB of
memory. On small systems it may be tricky to set the pipe max size to
prevent this from happening.

This patch makes it possible to enforce a per-user soft limit above
which new pipes will be limited to a single page, effectively limiting
them to 4 kB each, as well as a hard limit above which no new pipes may
be created for this user. This has the effect of protecting the system
against memory abuse without hurting other users, and still allowing
pipes to work correctly though with less data at once.

The limit are controlled by two new sysctls : pipe-user-pages-soft, and
pipe-user-pages-hard. Both may be disabled by setting them to zero. The
default soft limit allows the default number of FDs per process (1024)
to create pipes of the default size (64kB), thus reaching a limit of 64MB
before starting to create only smaller pipes. With 256 processes limited
to 1024 FDs each, this results in 1024*64kB + (256*1024 - 1024) * 4kB =
1084 MB of memory allocated for a user. The hard limit is disabled by
default to avoid breaking existing applications that make intensive use
of pipes (eg: for splicing).

Reported-by: socketpair@gmail.com
Reported-by: Tetsuo Handa 
Mitigates: CVE-2013-4312 (Linux 2.0+)
Suggested-by: Linus Torvalds 
Signed-off-by: Willy Tarreau 
Signed-off-by: Al Viro 
Signed-off-by: Jiri Slaby

unix: properly account for FDs passed over unix sockets

2016-03-07T13:32:05+00:00

[ Upstream commit 712f4aad406bb1ed67f3f98d04c044191f0ff593 ]

It is possible for a process to allocate and accumulate far more FDs than
the process' limit by sending them over a unix socket then closing them
to keep the process' fd count low.

This change addresses this problem by keeping track of the number of FDs
in flight per user and preventing non-privileged processes from having
more FDs in flight than their configured FD limit.

Cc: Michal Kubecek 
Reported-by: socketpair@gmail.com
Reported-by: Tetsuo Handa 
Mitigates: CVE-2013-4312 (Linux 2.0+)
Suggested-by: Linus Torvalds 
Acked-by: Hannes Frederic Sowa 
Signed-off-by: Willy Tarreau 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set

2014-10-31T14:11:24+00:00

commit 934f3072c17cc8886f4c043b47eeeb1b12f8de33 upstream.

commit 21caf2fc1931 ("mm: teach mm by current context info to not do I/O
during memory allocation") introduces PF_MEMALLOC_NOIO flag to avoid doing
I/O inside memory allocation, __GFP_IO is cleared when this flag is set,
but __GFP_FS implies __GFP_IO, it should also be cleared.  Or it may still
run into I/O, like in superblock shrinker.  And this will make the kernel
run into the deadlock case described in that commit.

See Dave Chinner's comment about io in superblock shrinker:

Filesystem shrinkers do indeed perform IO from the superblock shrinker and
have for years.  Even clean inodes can require IO before they can be freed
- e.g.  on an orphan list, need truncation of post-eof blocks, need to
wait for ordered operations to complete before it can be freed, etc.

IOWs, Ext4, btrfs and XFS all can issue and/or block on arbitrary amounts
of IO in the superblock shrinker context.  XFS, in particular, has been
doing transactions and IO from the VFS inode cache shrinker since it was
first introduced....

Fix this by clearing __GFP_FS in memalloc_noio_flags(), this function has
masked all the gfp_mask that will be passed into fs for the processes
setting PF_MEMALLOC_NOIO in the direct reclaim path.

v1 thread at: https://lkml.org/lkml/2014/9/3/32

Signed-off-by: Junxiao Bi 
Cc: Dave Chinner 
Cc: joyce.xue 
Cc: Ming Lei 
Cc: Trond Myklebust 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Jiri Slaby

mm: per-thread vma caching

2014-09-26T09:51:57+00:00

commit 615d6e8756c87149f2d4c1b93d471bca002bd849 upstream.

This patch is a continuation of efforts trying to optimize find_vma(),
avoiding potentially expensive rbtree walks to locate a vma upon faults.
The original approach (https://lkml.org/lkml/2013/11/1/410), where the
largest vma was also cached, ended up being too specific and random,
thus further comparison with other approaches were needed.  There are
two things to consider when dealing with this, the cache hit rate and
the latency of find_vma().  Improving the hit-rate does not necessarily
translate in finding the vma any faster, as the overhead of any fancy
caching schemes can be too high to consider.

We currently cache the last used vma for the whole address space, which
provides a nice optimization, reducing the total cycles in find_vma() by
up to 250%, for workloads with good locality.  On the other hand, this
simple scheme is pretty much useless for workloads with poor locality.
Analyzing ebizzy runs shows that, no matter how many threads are
running, the mmap_cache hit rate is less than 2%, and in many situations
below 1%.

The proposed approach is to replace this scheme with a small per-thread
cache, maximizing hit rates at a very low maintenance cost.
Invalidations are performed by simply bumping up a 32-bit sequence
number.  The only expensive operation is in the rare case of a seq
number overflow, where all caches that share the same address space are
flushed.  Upon a miss, the proposed replacement policy is based on the
page number that contains the virtual address in question.  Concretely,
the following results are seen on an 80 core, 8 socket x86-64 box:

1) System bootup: Most programs are single threaded, so the per-thread
   scheme does improve ~50% hit rate by just adding a few more slots to
   the cache.

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 50.61%   | 19.90            |
| patched        | 73.45%   | 13.58            |
+----------------+----------+------------------+

2) Kernel build: This one is already pretty good with the current
   approach as we're dealing with good locality.

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 75.28%   | 11.03            |
| patched        | 88.09%   | 9.31             |
+----------------+----------+------------------+

3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 70.66%   | 17.14            |
| patched        | 91.15%   | 12.57            |
+----------------+----------+------------------+

4) Ebizzy: There's a fair amount of variation from run to run, but this
   approach always shows nearly perfect hit rates, while baseline is just
   about non-existent.  The amounts of cycles can fluctuate between
   anywhere from ~60 to ~116 for the baseline scheme, but this approach
   reduces it considerably.  For instance, with 80 threads:

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 1.06%    | 91.54            |
| patched        | 99.97%   | 14.18            |
+----------------+----------+------------------+

[akpm@linux-foundation.org: fix nommu build, per Davidlohr]
[akpm@linux-foundation.org: document vmacache_valid() logic]
[akpm@linux-foundation.org: attempt to untangle header files]
[akpm@linux-foundation.org: add vmacache_find() BUG_ON]
[hughd@google.com: add vmacache_valid_mm() (from Oleg)]
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: adjust and enhance comments]
Signed-off-by: Davidlohr Bueso 
Reviewed-by: Rik van Riel 
Acked-by: Linus Torvalds 
Reviewed-by: Michel Lespinasse 
Cc: Oleg Nesterov 
Tested-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Mel Gorman 
Signed-off-by: Jiri Slaby

introduce for_each_thread() to replace the buggy while_each_thread()

2014-06-04T14:25:18+00:00

commit 0c740d0afc3bff0a097ad03a1c8df92757516f5c upstream.

while_each_thread() and next_thread() should die, almost every lockless
usage is wrong.

1. Unless g == current, the lockless while_each_thread() is not safe.

   while_each_thread(g, t) can loop forever if g exits, next_thread()
   can't reach the unhashed thread in this case. Note that this can
   happen even if g is the group leader, it can exec.

2. Even if while_each_thread() itself was correct, people often use
   it wrongly.

   It was never safe to just take rcu_read_lock() and loop unless
   you verify that pid_alive(g) == T, even the first next_thread()
   can point to the already freed/reused memory.

This patch adds signal_struct->thread_head and task->thread_node to
create the normal rcu-safe list with the stable head.  The new
for_each_thread(g, t) helper is always safe under rcu_read_lock() as
long as this task_struct can't go away.

Note: of course it is ugly to have both task_struct->thread_node and the
old task_struct->thread_group, we will kill it later, after we change
the users of while_each_thread() to use for_each_thread().

Perhaps we can kill it even before we convert all users, we can
reimplement next_thread(t) using the new thread_head/thread_node.  But
we can't do this right now because this will lead to subtle behavioural
changes.  For example, do/while_each_thread() always sees at least one
task, while for_each_thread() can do nothing if the whole thread group
has died.  Or thread_group_empty(), currently its semantics is not clear
unless thread_group_leader(p) and we need to audit the callers before we
can change it.

So this patch adds the new interface which has to coexist with the old
one for some time, hopefully the next changes will be more or less
straightforward and the old one will go away soon.

Signed-off-by: Oleg Nesterov 
Reviewed-by: Sergey Dyasly 
Tested-by: Sergey Dyasly 
Reviewed-by: Sameer Nanda 
Acked-by: David Rientjes 
Cc: "Eric W. Biederman" 
Cc: Frederic Weisbecker 
Cc: Mandeep Singh Baines 
Cc: "Ma, Xindong" 
Cc: Michal Hocko 
Cc: "Tu, Xiaobing" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Jiri Slaby

sched: declare pid_alive as inline

2014-05-23T09:01:38+00:00

commit 80e0b6e8a001361316a2d62b748fe677ec46b860 upstream.

We accidentally declared pid_alive without any extern/inline connotation.
Some platforms were fine with this, some like ia64 and mips were very angry.
If the function is inline, the prototype should be inline!

on ia64:
include/linux/sched.h:1718: warning: 'pid_alive' declared inline after
being called

Signed-off-by: Richard Guy Briggs 
Signed-off-by: Eric Paris 
Signed-off-by: Jiri Slaby

pid: get pid_t ppid of task in init_pid_ns

2014-05-23T09:01:16+00:00

commit ad36d28293936b03d6b7996e9d6aadfd73c0eb08 upstream.

Added the functions task_ppid_nr_ns() and task_ppid_nr() to abstract the lookup
of the PPID (real_parent's pid_t) of a process, including rcu locking, in the
arbitrary and init_pid_ns.
This provides an alternative to sys_getppid(), which is relative to the child
process' pid namespace.

(informed by ebiederman's 6c621b7e)
Cc: Eric W. Biederman 
Signed-off-by: Richard Guy Briggs 
Signed-off-by: Jiri Slaby

exec/ptrace: fix get_dumpable() incorrect tests

2013-11-29T19:27:58+00:00

commit d049f74f2dbe71354d43d393ac3a188947811348 upstream.

The get_dumpable() return value is not boolean.  Most users of the
function actually want to be testing for non-SUID_DUMP_USER(1) rather than
SUID_DUMP_DISABLE(0).  The SUID_DUMP_ROOT(2) is also considered a
protected state.  Almost all places did this correctly, excepting the two
places fixed in this patch.

Wrong logic:
    if (dumpable == SUID_DUMP_DISABLE) { /* be protective */ }
        or
    if (dumpable == 0) { /* be protective */ }
        or
    if (!dumpable) { /* be protective */ }

Correct logic:
    if (dumpable != SUID_DUMP_USER) { /* be protective */ }
        or
    if (dumpable != 1) { /* be protective */ }

Without this patch, if the system had set the sysctl fs/suid_dumpable=2, a
user was able to ptrace attach to processes that had dropped privileges to
that user.  (This may have been partially mitigated if Yama was enabled.)

The macros have been moved into the file that declares get/set_dumpable(),
which means things like the ia64 code can see them too.

CVE-2013-2929

Reported-by: Vasily Kulikov 
Signed-off-by: Kees Cook 
Cc: "Luck, Tony" 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sched, idle: Fix the idle polling state logic

2013-11-29T19:27:55+00:00

commit ea8117478918a4734586d35ff530721b682425be upstream.

Mike reported that commit 7d1a9417 ("x86: Use generic idle loop")
regressed several workloads and caused excessive reschedule
interrupts.

The patch in question failed to notice that the x86 code had an
inverted sense of the polling state versus the new generic code (x86:
default polling, generic: default !polling).

Fix the two prominent x86 mwait based idle drivers and introduce a few
new generic polling helpers (fixing the wrong smp_mb__after_clear_bit
usage).

Also switch the idle routines to using tif_need_resched() which is an
immediate TIF_NEED_RESCHED test as opposed to need_resched which will
end up being slightly different.

Reported-by: Mike Galbraith 
Signed-off-by: Peter Zijlstra 
Cc: lenb@kernel.org
Cc: tglx@linutronix.de
Link: http://lkml.kernel.org/n/tip-nc03imb0etuefmzybzj7sprf@git.kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

mm: memcg: handle non-error OOM situations more gracefully

2013-10-17T04:35:53+00:00

Commit 3812c8c8f395 ("mm: memcg: do not trap chargers with full
callstack on OOM") assumed that only a few places that can trigger a
memcg OOM situation do not return VM_FAULT_OOM, like optional page cache
readahead.  But there are many more and it's impractical to annotate
them all.

First of all, we don't want to invoke the OOM killer when the failed
allocation is gracefully handled, so defer the actual kill to the end of
the fault handling as well.  This simplifies the code quite a bit for
added bonus.

Second, since a failed allocation might not be the abrupt end of the
fault, the memcg OOM handler needs to be re-entrant until the fault
finishes for subsequent allocation attempts.  If an allocation is
attempted after the task already OOMed, allow it to bypass the limit so
that it can quickly finish the fault and invoke the OOM killer.

Reported-by: azurIt 
Signed-off-by: Johannes Weiner 
Cc: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds