linux-stable.git/mm, branch v3.16.52

ptrace: Don't allow accessing an undumpable mm

2018-01-01T20:52:11+00:00

commit 84d77d3f06e7e8dea057d10e8ec77ad71f721be3 upstream.

It is the reasonable expectation that if an executable file is not
readable there will be no way for a user without special privileges to
read the file.  This is enforced in ptrace_attach but if ptrace
is already attached before exec there is no enforcement for read-only
executables.

As the only way to read such an mm is through access_process_vm
spin a variant called ptrace_access_vm that will fail if the
target process is not being ptraced by the current process, or
the current process did not have sufficient privileges when ptracing
began to read the target processes mm.

In the ptrace implementations replace access_process_vm by
ptrace_access_vm.  There remain several ptrace sites that still use
access_process_vm as they are reading the target executables
instructions (for kernel consumption) or register stacks.  As such it
does not appear necessary to add a permission check to those calls.

This bug has always existed in Linux.

Fixes: v1.0
Reported-by: Andy Lutomirski 
Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.16:
 - Pass around only a write flag, not gup_flags
 - Adjust context]
Signed-off-by: Ben Hutchings

mm: Add a user_ns owner to mm_struct and fix ptrace permission checks

2018-01-01T20:52:10+00:00

commit bfedb589252c01fa505ac9f6f2a3d5d68d707ef4 upstream.

During exec dumpable is cleared if the file that is being executed is
not readable by the user executing the file.  A bug in
ptrace_may_access allows reading the file if the executable happens to
enter into a subordinate user namespace (aka clone(CLONE_NEWUSER),
unshare(CLONE_NEWUSER), or setns(fd, CLONE_NEWUSER).

This problem is fixed with only necessary userspace breakage by adding
a user namespace owner to mm_struct, captured at the time of exec, so
it is clear in which user namespace CAP_SYS_PTRACE must be present in
to be able to safely give read permission to the executable.

The function ptrace_may_access is modified to verify that the ptracer
has CAP_SYS_ADMIN in task->mm->user_ns instead of task->cred->user_ns.
This ensures that if the task changes it's cred into a subordinate
user namespace it does not become ptraceable.

The function ptrace_attach is modified to only set PT_PTRACE_CAP when
CAP_SYS_PTRACE is held over task->mm->user_ns.  The intent of
PT_PTRACE_CAP is to be a flag to note that whatever permission changes
the task might go through the tracer has sufficient permissions for
it not to be an issue.  task->cred->user_ns is always the same
as or descendent of mm->user_ns.  Which guarantees that having
CAP_SYS_PTRACE over mm->user_ns is the worst case for the tasks
credentials.

To prevent regressions mm->dumpable and mm->user_ns are not considered
when a task has no mm.  As simply failing ptrace_may_attach causes
regressions in privileged applications attempting to read things
such as /proc//stat

Acked-by: Kees Cook 
Tested-by: Cyrill Gorcunov 
Fixes: 8409cca70561 ("userns: allow ptrace from non-init user namespaces")
Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

mm, thp: Do not make page table dirty unconditionally in touch_p[mu]d()

2018-01-01T20:52:09+00:00

commit a8f97366452ed491d13cf1e44241bc0b5740b1f0 upstream.

Currently, we unconditionally make page table dirty in touch_pmd().
It may result in false-positive can_follow_write_pmd().

We may avoid the situation, if we would only make the page table entry
dirty if caller asks for write access -- FOLL_WRITE.

The patch also changes touch_pud() in the same way.

Signed-off-by: Kirill A. Shutemov 
Cc: Michal Hocko 
Cc: Hugh Dickins 
Signed-off-by: Linus Torvalds 
[carnil: backport for 3.16:
 - Adjust context
 - Drop specific part for PUD-sized transparent hugepages. Support
   for PUD-sized transparent hugepages was added in v4.11-rc1
]
Signed-off-by: Ben Hutchings

mm/memory_hotplug: define find_{smallest|biggest}_section_pfn as unsigned long

2018-01-01T20:51:48+00:00

commit d09b0137d204bebeaafed672bc5a244e9ac92edb upstream.

find_{smallest|biggest}_section_pfn()s find the smallest/biggest section
and return the pfn of the section.  But the functions are defined as int.
So the functions always return 0x00000000 - 0xffffffff.  It means if
memory address is over 16TB, the functions does not work correctly.

To handle 64 bit value, the patch defines
find_{smallest|biggest}_section_pfn() as unsigned long.

Fixes: 815121d2b5cd ("memory_hotplug: clear zone when removing the memory")
Link: http://lkml.kernel.org/r/d9d5593a-d0a4-c4be-ab08-493df59a85c6@gmail.com
Signed-off-by: Yasuaki Ishimatsu 
Acked-by: Michal Hocko 
Cc: Xishi Qiu 
Cc: Reza Arbab 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm/memory_hotplug: change pfn_to_section_nr/section_nr_to_pfn macro to inline function

2018-01-01T20:51:48+00:00

commit 1dd2bfc86818ddbc95f98e312e7704350223fd7d upstream.

pfn_to_section_nr() and section_nr_to_pfn() are defined as macro.
pfn_to_section_nr() has no issue even if it is defined as macro.  But
section_nr_to_pfn() has overflow issue if sec is defined as int.

section_nr_to_pfn() just shifts sec by PFN_SECTION_SHIFT.  If sec is
defined as unsigned long, section_nr_to_pfn() returns pfn as 64 bit value.
But if sec is defined as int, section_nr_to_pfn() returns pfn as 32 bit
value.

__remove_section() calculates start_pfn using section_nr_to_pfn() and
scn_nr defined as int.  So if hot-removed memory address is over 16TB,
overflow issue occurs and section_nr_to_pfn() does not calculate correct
pfn.

To make callers use proper arg, the patch changes the macros to inline
functions.

Fixes: 815121d2b5cd ("memory_hotplug: clear zone when removing the memory")
Link: http://lkml.kernel.org/r/e643a387-e573-6bbf-d418-c60c8ee3d15e@gmail.com
Signed-off-by: Yasuaki Ishimatsu 
Acked-by: Michal Hocko 
Cc: Xishi Qiu 
Cc: Reza Arbab 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm/hugetlb: improve locking in dissolve_free_huge_pages()

2017-11-11T13:33:43+00:00

commit eb03aa008561004257900983193d024e57abdd96 upstream.

For every pfn aligned to minimum_order, dissolve_free_huge_pages() will
call dissolve_free_huge_page() which takes the hugetlb spinlock, even if
the page is not huge at all or a hugepage that is in-use.

Improve this by doing the PageHuge() and page_count() checks already in
dissolve_free_huge_pages() before calling dissolve_free_huge_page().  In
dissolve_free_huge_page(), when holding the spinlock, those checks need
to be revalidated.

Link: http://lkml.kernel.org/r/20160926172811.94033-4-gerald.schaefer@de.ibm.com
Signed-off-by: Gerald Schaefer 
Acked-by: Michal Hocko 
Acked-by: Naoya Horiguchi 
Cc: "Kirill A . Shutemov" 
Cc: Vlastimil Babka 
Cc: Mike Kravetz 
Cc: "Aneesh Kumar K . V" 
Cc: Martin Schwidefsky 
Cc: Heiko Carstens 
Cc: Rui Teng 
Cc: Dave Hansen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Arnd Bergmann 
Signed-off-by: Ben Hutchings

mm/init: fix zone boundary creation

2017-11-11T13:33:41+00:00

commit 90cae1fe1c3540f791d5b8e025985fa5e699b2bb upstream.

As a part of memory initialisation the architecture passes an array to
free_area_init_nodes() which specifies the max PFN of each memory zone.
This array is not necessarily monotonic (due to unused zones) so this
array is parsed to build monotonic lists of the min and max PFN for each
zone.  ZONE_MOVABLE is special cased here as its limits are managed by
the mm subsystem rather than the architecture.  Unfortunately, this
special casing is broken when ZONE_MOVABLE is the not the last zone in
the zone list.  The core of the issue is:

	if (i == ZONE_MOVABLE)
		continue;
	arch_zone_lowest_possible_pfn[i] =
		arch_zone_highest_possible_pfn[i-1];

As ZONE_MOVABLE is skipped the lowest_possible_pfn of the next zone will
be set to zero.  This patch fixes this bug by adding explicitly tracking
where the next zone should start rather than relying on the contents
arch_zone_highest_possible_pfn[].

Thie is low priority.  To get bitten by this you need to enable a zone
that appears after ZONE_MOVABLE in the zone_type enum.  As far as I can
tell this means running a kernel with ZONE_DEVICE or ZONE_CMA enabled,
so I can't see this affecting too many people.

I only noticed this because I've been fiddling with ZONE_DEVICE on
powerpc and 4.6 broke my test kernel.  This bug, in conjunction with the
changes in Taku Izumi's kernelcore=mirror patch (d91749c1dda71) and
powerpc being the odd architecture which initialises max_zone_pfn[] to
~0ul instead of 0 caused all of system memory to be placed into
ZONE_DEVICE at boot, followed a panic since device memory cannot be used
for kernel allocations.  I've already submitted a patch to fix the
powerpc specific bits, but I figured this should be fixed too.

Link: http://lkml.kernel.org/r/1462435033-15601-1-git-send-email-oohall@gmail.com
Signed-off-by: Oliver O'Halloran 
Cc: Anton Blanchard 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Cc: Arnd Bergmann 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Arnd Bergmann 
Signed-off-by: Ben Hutchings

PM/hibernate: touch NMI watchdog when creating snapshot

2017-11-11T13:33:27+00:00

commit 556b969a1cfe2686aae149137fa1dfcac0eefe54 upstream.

There is a problem that when counting the pages for creating the
hibernation snapshot will take significant amount of time, especially on
system with large memory.  Since the counting job is performed with irq
disabled, this might lead to NMI lockup.  The following warning were
found on a system with 1.5TB DRAM:

  Freezing user space processes ... (elapsed 0.002 seconds) done.
  OOM killer disabled.
  PM: Preallocating image memory...
  NMI watchdog: Watchdog detected hard LOCKUP on cpu 27
  CPU: 27 PID: 3128 Comm: systemd-sleep Not tainted 4.13.0-0.rc2.git0.1.fc27.x86_64 #1
  task: ffff9f01971ac000 task.stack: ffffb1a3f325c000
  RIP: 0010:memory_bm_find_bit+0xf4/0x100
  Call Trace:
   swsusp_set_page_free+0x2b/0x30
   mark_free_pages+0x147/0x1c0
   count_data_pages+0x41/0xa0
   hibernate_preallocate_memory+0x80/0x450
   hibernation_snapshot+0x58/0x410
   hibernate+0x17c/0x310
   state_store+0xdf/0xf0
   kobj_attr_store+0xf/0x20
   sysfs_kf_write+0x37/0x40
   kernfs_fop_write+0x11c/0x1a0
   __vfs_write+0x37/0x170
   vfs_write+0xb1/0x1a0
   SyS_write+0x55/0xc0
   entry_SYSCALL_64_fastpath+0x1a/0xa5
  ...
  done (allocated 6590003 pages)
  PM: Allocated 26360012 kbytes in 19.89 seconds (1325.28 MB/s)

It has taken nearly 20 seconds(2.10GHz CPU) thus the NMI lockup was
triggered.  In case the timeout of the NMI watch dog has been set to 1
second, a safe interval should be 6590003/20 = 320k pages in theory.
However there might also be some platforms running at a lower frequency,
so feed the watchdog every 100k pages.

[yu.c.chen@intel.com: simplification]
  Link: http://lkml.kernel.org/r/1503460079-29721-1-git-send-email-yu.c.chen@intel.com
[yu.c.chen@intel.com: use interval of 128k instead of 100k to avoid modulus]
Link: http://lkml.kernel.org/r/1503328098-5120-1-git-send-email-yu.c.chen@intel.com
Signed-off-by: Chen Yu 
Reported-by: Jan Filipcewicz 
Suggested-by: Michal Hocko 
Reviewed-by: Michal Hocko 
Acked-by: Rafael J. Wysocki 
Cc: Mel Gorman 
Cc: Vlastimil Babka 
Cc: Len Brown 
Cc: Dan Williams 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

mm/mempolicy: fix use after free when calling get_mempolicy

2017-11-11T13:33:22+00:00

commit 73223e4e2e3867ebf033a5a8eb2e5df0158ccc99 upstream.

I hit a use after free issue when executing trinity and repoduced it
with KASAN enabled.  The related call trace is as follows.

  BUG: KASan: use after free in SyS_get_mempolicy+0x3c8/0x960 at addr ffff8801f582d766
  Read of size 2 by task syz-executor1/798

  INFO: Allocated in mpol_new.part.2+0x74/0x160 age=3 cpu=1 pid=799
     __slab_alloc+0x768/0x970
     kmem_cache_alloc+0x2e7/0x450
     mpol_new.part.2+0x74/0x160
     mpol_new+0x66/0x80
     SyS_mbind+0x267/0x9f0
     system_call_fastpath+0x16/0x1b
  INFO: Freed in __mpol_put+0x2b/0x40 age=4 cpu=1 pid=799
     __slab_free+0x495/0x8e0
     kmem_cache_free+0x2f3/0x4c0
     __mpol_put+0x2b/0x40
     SyS_mbind+0x383/0x9f0
     system_call_fastpath+0x16/0x1b
  INFO: Slab 0xffffea0009cb8dc0 objects=23 used=8 fp=0xffff8801f582de40 flags=0x200000000004080
  INFO: Object 0xffff8801f582d760 @offset=5984 fp=0xffff8801f582d600

  Bytes b4 ffff8801f582d750: ae 01 ff ff 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a  ........ZZZZZZZZ
  Object ffff8801f582d760: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
  Object ffff8801f582d770: 6b 6b 6b 6b 6b 6b 6b a5                          kkkkkkk.
  Redzone ffff8801f582d778: bb bb bb bb bb bb bb bb                          ........
  Padding ffff8801f582d8b8: 5a 5a 5a 5a 5a 5a 5a 5a                          ZZZZZZZZ
  Memory state around the buggy address:
  ffff8801f582d600: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801f582d680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  >ffff8801f582d700: fc fc fc fc fc fc fc fc fc fc fc fc fb fb fb fc

!shared memory policy is not protected against parallel removal by other
thread which is normally protected by the mmap_sem.  do_get_mempolicy,
however, drops the lock midway while we can still access it later.

Early premature up_read is a historical artifact from times when
put_user was called in this path see https://lwn.net/Articles/124754/
but that is gone since 8bccd85ffbaf ("[PATCH] Implement sys_* do_*
layering in the memory policy layer.").  but when we have the the
current mempolicy ref count model.  The issue was introduced
accordingly.

Fix the issue by removing the premature release.

Link: http://lkml.kernel.org/r/1502950924-27521-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang 
Acked-by: Michal Hocko 
Cc: Minchan Kim 
Cc: Vlastimil Babka 
Cc: David Rientjes 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

mm: migrate: prevent racy access to tlb_flush_pending

2017-11-11T13:33:19+00:00

commit 16af97dc5a8975371a83d9e30a64038b48f40a2d upstream.

Patch series "fixes of TLB batching races", v6.

It turns out that Linux TLB batching mechanism suffers from various
races.  Races that are caused due to batching during reclamation were
recently handled by Mel and this patch-set deals with others.  The more
fundamental issue is that concurrent updates of the page-tables allow
for TLB flushes to be batched on one core, while another core changes
the page-tables.  This other core may assume a PTE change does not
require a flush based on the updated PTE value, while it is unaware that
TLB flushes are still pending.

This behavior affects KSM (which may result in memory corruption) and
MADV_FREE and MADV_DONTNEED (which may result in incorrect behavior).  A
proof-of-concept can easily produce the wrong behavior of MADV_DONTNEED.
Memory corruption in KSM is harder to produce in practice, but was
observed by hacking the kernel and adding a delay before flushing and
replacing the KSM page.

Finally, there is also one memory barrier missing, which may affect
architectures with weak memory model.

This patch (of 7):

Setting and clearing mm->tlb_flush_pending can be performed by multiple
threads, since mmap_sem may only be acquired for read in
task_numa_work().  If this happens, tlb_flush_pending might be cleared
while one of the threads still changes PTEs and batches TLB flushes.

This can lead to the same race between migration and
change_protection_range() that led to the introduction of
tlb_flush_pending.  The result of this race was data corruption, which
means that this patch also addresses a theoretically possible data
corruption.

An actual data corruption was not observed, yet the race was was
confirmed by adding assertion to check tlb_flush_pending is not set by
two threads, adding artificial latency in change_protection_range() and
using sysctl to reduce kernel.numa_balancing_scan_delay_ms.

Link: http://lkml.kernel.org/r/20170802000818.4760-2-namit@vmware.com
Fixes: 20841405940e ("mm: fix TLB flush race between migration, and
change_protection_range")
Signed-off-by: Nadav Amit 
Acked-by: Mel Gorman 
Acked-by: Rik van Riel 
Acked-by: Minchan Kim 
Cc: Andy Lutomirski 
Cc: Hugh Dickins 
Cc: "David S. Miller" 
Cc: Andrea Arcangeli 
Cc: Heiko Carstens 
Cc: Ingo Molnar 
Cc: Jeff Dike 
Cc: Martin Schwidefsky 
Cc: Mel Gorman 
Cc: Russell King 
Cc: Sergey Senozhatsky 
Cc: Tony Luck 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16:
 - Drop change to dump_mm()
 - Adjust context]
Signed-off-by: Ben Hutchings