linux-stable.git/mm, branch v3.16.45

Allow stack to grow up to address space limit

2017-07-02T16:13:02+00:00

commit bd726c90b6b8ce87602208701b208a208e6d5600 upstream.

Fix expand_upwards() on architectures with an upward-growing stack (parisc,
metag and partly IA-64) to allow the stack to reliably grow exactly up to
the address space limit given by TASK_SIZE.

Signed-off-by: Helge Deller 
Acked-by: Hugh Dickins 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm: fix new crash in unmapped_area_topdown()

2017-07-02T16:13:02+00:00

commit f4cb767d76cf7ee72f97dd76f6cfa6c76a5edc89 upstream.

Trinity gets kernel BUG at mm/mmap.c:1963! in about 3 minutes of
mmap testing.  That's the VM_BUG_ON(gap_end < gap_start) at the
end of unmapped_area_topdown().  Linus points out how MAP_FIXED
(which does not have to respect our stack guard gap intentions)
could result in gap_end below gap_start there.  Fix that, and
the similar case in its alternative, unmapped_area().

Fixes: 1be7107fbe18 ("mm: larger stack guard gap, between vmas")
Reported-by: Dave Jones 
Debugged-by: Linus Torvalds 
Signed-off-by: Hugh Dickins 
Acked-by: Michal Hocko 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm: larger stack guard gap, between vmas

2017-07-02T16:13:02+00:00

commit 1be7107fbe18eed3e319a6c3e83c78254b693acb upstream.

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov 
Original-patch-by: Michal Hocko 
Signed-off-by: Hugh Dickins 
Acked-by: Michal Hocko 
Tested-by: Helge Deller  # parisc
Signed-off-by: Linus Torvalds 
[Hugh Dickins: Backported to 3.16]
Signed-off-by: Ben Hutchings

mm/mempolicy.c: fix error handling in set_mempolicy and mbind.

2017-06-05T20:17:21+00:00

commit cf01fb9985e8deb25ccf0ea54d916b8871ae0e62 upstream.

In the case that compat_get_bitmap fails we do not want to copy the
bitmap to the user as it will contain uninitialized stack data and leak
sensitive data.

Signed-off-by: Chris Salls 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm: do not access page->mapping directly on page_endio

2017-06-05T20:17:16+00:00

commit dd8416c47715cf324c9a16f13273f9fda87acfed upstream.

With rw_page, page_endio is used for completing IO on a page and it
propagates write error to the address space if the IO fails.  The
problem is it accesses page->mapping directly which might be okay for
file-backed pages but it shouldn't for anonymous page.  Otherwise, it
can corrupt one of field from anon_vma under us and system goes panic
randomly.

swap_writepage
  bdev_writepage
    ops->rw_page

I encountered the BUG during developing new zram feature and it was
really hard to figure it out because it made random crash, somtime
mmap_sem lockdep, sometime other places where places never related to
zram/zsmalloc, and not reproducible with some configuration.

When I consider how that bug is subtle and people do fast-swap test with
brd, it's worth to add stable mark, I think.

Fixes: dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()")
Signed-off-by: Minchan Kim 
Acked-by: Michal Hocko 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm: vmpressure: fix sending wrong events on underflow

2017-06-05T20:17:16+00:00

commit e1587a4945408faa58d0485002c110eb2454740c upstream.

At the end of a window period, if the reclaimed pages is greater than
scanned, an unsigned underflow can result in a huge pressure value and
thus a critical event.  Reclaimed pages is found to go higher than
scanned because of the addition of reclaimed slab pages to reclaimed in
shrink_node without a corresponding increment to scanned pages.

Minchan Kim mentioned that this can also happen in the case of a THP
page where the scanned is 1 and reclaimed could be 512.

Link: http://lkml.kernel.org/r/1486641577-11685-1-git-send-email-vinmenon@codeaurora.org
Signed-off-by: Vinayak Menon 
Acked-by: Minchan Kim 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: Mel Gorman 
Cc: Vlastimil Babka 
Cc: Rik van Riel 
Cc: Vladimir Davydov 
Cc: Anton Vorontsov 
Cc: Shiraz Hashim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm/page_alloc: fix nodes for reclaim in fast path

2017-06-05T20:17:16+00:00

commit e02dc017c3032dcdce1b993af0db135462e1b4b7 upstream.

When @node_reclaim_node isn't 0, the page allocator tries to reclaim
pages if the amount of free memory in the zones are below the low
watermark.  On Power platform, none of NUMA nodes are scanned for page
reclaim because no nodes match the condition in zone_allows_reclaim().
On Power platform, RECLAIM_DISTANCE is set to 10 which is the distance
of Node-A to Node-A.  So the preferred node even won't be scanned for
page reclaim.

   __alloc_pages_nodemask()
   get_page_from_freelist()
      zone_allows_reclaim()

Anton proposed the test code as below:

   # cat alloc.c
      :
   int main(int argc, char *argv[])
   {
	void *p;
	unsigned long size;
	unsigned long start, end;

	start = time(NULL);
	size = strtoul(argv[1], NULL, 0);
	printf("To allocate %ldGB memory\n", size);

	size <<= 30;
	p = malloc(size);
	assert(p);
	memset(p, 0, size);

	end = time(NULL);
	printf("Used time: %ld seconds\n", end - start);
	sleep(3600);
	return 0;
   }

The system I use for testing has two NUMA nodes.  Both have 128GB
memory.  In below scnario, the page caches on node#0 should be reclaimed
when it encounters pressure to accommodate request of allocation.

   # echo 2 > /proc/sys/vm/zone_reclaim_mode; \
     sync; \
     echo 3 > /proc/sys/vm/drop_caches; \
   # taskset -c 0 cat file.32G > /dev/null; \
     grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:       33619712 kB
   # taskset -c 0 ./alloc 128
   # grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:       33619840 kB
   # grep MemFree /sys/devices/system/node/node0/meminfo
     Node 0 MemFree:          186816 kB

With the patch applied, the pagecache on node-0 is reclaimed when its
free memory is running out.  It's the expected behaviour.

   # echo 2 > /proc/sys/vm/zone_reclaim_mode; \
     sync; \
     echo 3 > /proc/sys/vm/drop_caches
   # taskset -c 0 cat file.32G > /dev/null; \
     grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:       33605568 kB
   # taskset -c 0 ./alloc 128
   # grep FilePages /sys/devices/system/node/node0/meminfo
     Node 0 FilePages:        1379520 kB
   # grep MemFree /sys/devices/system/node/node0/meminfo
     Node 0 MemFree:           317120 kB

Fixes: 5f7a75acdb24 ("mm: page_alloc: do not cache reclaim distances")
Link: http://lkml.kernel.org/r/1486532455-29613-1-git-send-email-gwshan@linux.vnet.ibm.com
Signed-off-by: Gavin Shan 
Acked-by: Mel Gorman 
Acked-by: Michal Hocko 
Cc: Anton Blanchard 
Cc: Michael Ellerman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm/huge_memory.c: fix up "mm/huge_memory.c: respect FOLL_FORCE/FOLL_COW for thp" backport

2017-06-05T20:16:44+00:00

This is a stable follow up fix for an incorrect backport. The issue is
not present in the upstream kernel.

Miroslav has noticed the following splat when testing my 3.2 forward
port of 8310d48b125d ("mm/huge_memory.c: respect FOLL_FORCE/FOLL_COW for
thp") to 3.12:

BUG: Bad page state in process a.out  pfn:26400
page:ffffea000085e000 count:0 mapcount:1 mapping:          (null) index:0x7f049d600
page flags: 0x1fffff80108018(uptodate|dirty|head|swapbacked)
page dumped because: nonzero mapcount
[iii]
CPU: 2 PID: 5926 Comm: a.out Tainted: G            E    3.12.61-0-default #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
 0000000000000000 ffffffff81515830 ffffea000085e000 ffffffff81800ad7
 ffffffff815118a5 ffffea000085e000 0000000000000000 000fffff80000000
 ffffffff81140f18 fff000007c000000 ffffea000085e000 0000000000000009
Call Trace:
 [] dump_trace+0x7d/0x2d0
 [] show_stack_log_lvl+0x94/0x170
 [] show_stack+0x21/0x50
 [] dump_stack+0x5d/0x78
 [] bad_page.part.67+0xe8/0x102
 [] free_pages_prepare+0x198/0x1b0
 [] __free_pages_ok+0x15/0xd0
 [] __access_remote_vm+0x7c/0x1e0
 [] mem_rw.isra.13+0x14b/0x1a0
 [] vfs_write+0xb8/0x1e0
 [] SyS_pwrite64+0x6b/0xa0
 [] system_call_fastpath+0x16/0x1b
 [<00007f049da18573>] 0x7f049da18572

The problem is that the original 3.2 backport didn't return NULL page on
the FOLL_COW page and so the page got reused.

Reported-and-tested-by: Miroslav Beneš 
Signed-off-by: Michal Hocko 
Signed-off-by: Ben Hutchings

vfs: Commit to never having exectuables on proc and sysfs.

2017-04-04T21:21:56+00:00

commit 22f6b4d34fcf039c63a94e7670e0da24f8575a5a upstream.

Today proc and sysfs do not contain any executable files.  Several
applications today mount proc or sysfs without noexec and nosuid and
then depend on there being no exectuables files on proc or sysfs.
Having any executable files show on proc or sysfs would cause
a user space visible regression, and most likely security problems.

Therefore commit to never allowing executables on proc and sysfs by
adding a new flag to mark them as filesystems without executables and
enforce that flag.

Test the flag where MNT_NOEXEC is tested today, so that the only user
visible effect will be that exectuables will be treated as if the
execute bit is cleared.

The filesystems proc and sysfs do not currently incoporate any
executable files so this does not result in any user visible effects.

This makes it unnecessary to vet changes to proc and sysfs tightly for
adding exectuable files or changes to chattr that would modify
existing files, as no matter what the individual file say they will
not be treated as exectuable files by the vfs.

Not having to vet changes to closely is important as without this we
are only one proc_create call (or another goof up in the
implementation of notify_change) from having problematic executables
on proc.  Those mistakes are all too easy to make and would create
a situation where there are security issues or the assumptions of
some program having to be broken (and cause userspace regressions).

Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.16: we don't have super_block::s_iflags; use
 file_system_type::fs_flags instead]
Signed-off-by: Ben Hutchings

mm, fs: check for fatal signals in do_generic_file_read()

2017-03-16T02:27:09+00:00

commit 5abf186a30a89d5b9c18a6bf93a2c192c9fd52f6 upstream.

do_generic_file_read() can be told to perform a large request from
userspace.  If the system is under OOM and the reading task is the OOM
victim then it has an access to memory reserves and finishing the full
request can lead to the full memory depletion which is dangerous.  Make
sure we rather go with a short read and allow the killed task to
terminate.

Link: http://lkml.kernel.org/r/20170201092706.9966-3-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reviewed-by: Christoph Hellwig 
Cc: Tetsuo Handa 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings