linux-toradex.git/mm, branch v4.9.42

mm: don't dereference struct page fields of invalid pages

2017-08-11T15:49:36+00:00

[ Upstream commit f073bdc51771f5a5c7a8d1191bfc3ae371d44de7 ]

The VM_BUG_ON() check in move_freepages() checks whether the node id of
a page matches the node id of its zone.  However, it does this before
having checked whether the struct page pointer refers to a valid struct
page to begin with.  This is guaranteed in most cases, but may not be
the case if CONFIG_HOLES_IN_ZONE=y.

So reorder the VM_BUG_ON() with the pfn_valid_within() check.

Link: http://lkml.kernel.org/r/1481706707-6211-2-git-send-email-ard.biesheuvel@linaro.org
Signed-off-by: Ard Biesheuvel 
Acked-by: Will Deacon 
Cc: Catalin Marinas 
Cc: Hanjun Guo 
Cc: Yisheng Xie 
Cc: Robert Richter 
Cc: James Morse 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

mm/page_alloc: Remove kernel address exposure in free_reserved_area()

2017-08-11T15:49:29+00:00

commit adb1fe9ae2ee6ef6bc10f3d5a588020e7664dfa7 upstream.

Linus suggested we try to remove some of the low-hanging fruit related
to kernel address exposure in dmesg.  The only leaks I see on my local
system are:

  Freeing SMP alternatives memory: 32K (ffffffff9e309000 - ffffffff9e311000)
  Freeing initrd memory: 10588K (ffffa0b736b42000 - ffffa0b737599000)
  Freeing unused kernel memory: 3592K (ffffffff9df87000 - ffffffff9e309000)
  Freeing unused kernel memory: 1352K (ffffa0b7288ae000 - ffffa0b728a00000)
  Freeing unused kernel memory: 632K (ffffa0b728d62000 - ffffa0b728e00000)

Linus says:

  "I suspect we should just remove [the addresses in the 'Freeing'
   messages]. I'm sure they are useful in theory, but I suspect they
   were more useful back when the whole "free init memory" was
   originally done.

   These days, if we have a use-after-free, I suspect the init-mem
   situation is the easiest situation by far. Compared to all the dynamic
   allocations which are much more likely to show it anyway. So having
   debug output for that case is likely not all that productive."

With this patch the freeing messages now look like this:

  Freeing SMP alternatives memory: 32K
  Freeing initrd memory: 10588K
  Freeing unused kernel memory: 3592K
  Freeing unused kernel memory: 1352K
  Freeing unused kernel memory: 632K

Suggested-by: Linus Torvalds 
Signed-off-by: Josh Poimboeuf 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/6836ff90c45b71d38e5d4405aec56fa9e5d1d4b2.1477405374.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar 
Cc: Kees Cook 
Signed-off-by: Greg Kroah-Hartman

mm, mprotect: flush TLB if potentially racing with a parallel reclaim leaving stale TLB entries

2017-08-11T15:49:29+00:00

commit 3ea277194daaeaa84ce75180ec7c7a2075027a68 upstream.

Nadav Amit identified a theoritical race between page reclaim and
mprotect due to TLB flushes being batched outside of the PTL being held.

He described the race as follows:

        CPU0                            CPU1
        ----                            ----
                                        user accesses memory using RW PTE
                                        [PTE now cached in TLB]
        try_to_unmap_one()
        ==> ptep_get_and_clear()
        ==> set_tlb_ubc_flush_pending()
                                        mprotect(addr, PROT_READ)
                                        ==> change_pte_range()
                                        ==> [ PTE non-present - no flush ]

                                        user writes using cached RW PTE
        ...

        try_to_unmap_flush()

The same type of race exists for reads when protecting for PROT_NONE and
also exists for operations that can leave an old TLB entry behind such
as munmap, mremap and madvise.

For some operations like mprotect, it's not necessarily a data integrity
issue but it is a correctness issue as there is a window where an
mprotect that limits access still allows access.  For munmap, it's
potentially a data integrity issue although the race is massive as an
munmap, mmap and return to userspace must all complete between the
window when reclaim drops the PTL and flushes the TLB.  However, it's
theoritically possible so handle this issue by flushing the mm if
reclaim is potentially currently batching TLB flushes.

Other instances where a flush is required for a present pte should be ok
as either the page lock is held preventing parallel reclaim or a page
reference count is elevated preventing a parallel free leading to
corruption.  In the case of page_mkclean there isn't an obvious path
that userspace could take advantage of without using the operations that
are guarded by this patch.  Other users such as gup as a race with
reclaim looks just at PTEs.  huge page variants should be ok as they
don't race with reclaim.  mincore only looks at PTEs.  userfault also
should be ok as if a parallel reclaim takes place, it will either fault
the page back in or read some of the data before the flush occurs
triggering a fault.

Note that a variant of this patch was acked by Andy Lutomirski but this
was for the x86 parts on top of his PCID work which didn't make the 4.13
merge window as expected.  His ack is dropped from this version and
there will be a follow-on patch on top of PCID that will include his
ack.

[akpm@linux-foundation.org: tweak comments]
[akpm@linux-foundation.org: fix spello]
Link: http://lkml.kernel.org/r/20170717155523.emckq2esjro6hf3z@suse.de
Reported-by: Nadav Amit 
Signed-off-by: Mel Gorman 
Cc: Andy Lutomirski 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm: fix overflow check in expand_upwards()

2017-07-21T05:42:22+00:00

commit 37511fb5c91db93d8bd6e3f52f86e5a7ff7cfcdf upstream.

JÃ¶rn Engel noticed that the expand_upwards() function might not return
-ENOMEM in case the requested address is (unsigned long)-PAGE_SIZE and
if the architecture didn't defined TASK_SIZE as multiple of PAGE_SIZE.

Affected architectures are arm, frv, m68k, blackfin, h8300 and xtensa
which all define TASK_SIZE as 0xffffffff, but since none of those have
an upwards-growing stack we currently have no actual issue.

Nevertheless let's fix this just in case any of the architectures with
an upward-growing stack (currently parisc, metag and partly ia64) define
TASK_SIZE similar.

Link: http://lkml.kernel.org/r/20170702192452.GA11868@p100.box
Fixes: bd726c90b6b8 ("Allow stack to grow up to address space limit")
Signed-off-by: Helge Deller 
Reported-by: Jörn Engel 
Cc: Hugh Dickins 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/list_lru.c: fix list_lru_count_node() to be race free

2017-07-21T05:42:21+00:00

commit 2c80cd57c74339889a8752b20862a16c28929c3a upstream.

list_lru_count_node() iterates over all memcgs to get the total number of
entries on the node but it can race with memcg_drain_all_list_lrus(),
which migrates the entries from a dead cgroup to another.  This can return
incorrect number of entries from list_lru_count_node().

Fix this by keeping track of entries per node and simply return it in
list_lru_count_node().

Link: http://lkml.kernel.org/r/1498707555-30525-1-git-send-email-stummala@codeaurora.org
Signed-off-by: Sahitya Tummala 
Acked-by: Vladimir Davydov 
Cc: Jan Kara 
Cc: Alexander Polakov 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

thp, mm: fix crash due race in MADV_FREE handling

2017-07-21T05:42:21+00:00

commit bbf29ffc7f963bb894f84f0580c70cfea01c3892 upstream.

Reinette reported the following crash:

  BUG: Bad page state in process log2exe  pfn:57600
  page:ffffea00015d8000 count:0 mapcount:0 mapping:          (null) index:0x20200
  flags: 0x4000000000040019(locked|uptodate|dirty|swapbacked)
  raw: 4000000000040019 0000000000000000 0000000000020200 00000000ffffffff
  raw: ffffea00015d8020 ffffea00015d8020 0000000000000000 0000000000000000
  page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
  bad because of flags: 0x1(locked)
  Modules linked in: rfcomm 8021q bnep intel_rapl x86_pkg_temp_thermal coretemp efivars btusb btrtl btbcm pwm_lpss_pci snd_hda_codec_hdmi btintel pwm_lpss snd_hda_codec_realtek snd_soc_skl snd_hda_codec_generic snd_soc_skl_ipc spi_pxa2xx_platform snd_soc_sst_ipc snd_soc_sst_dsp i2c_designware_platform i2c_designware_core snd_hda_ext_core snd_soc_sst_match snd_hda_intel snd_hda_codec mei_me snd_hda_core mei snd_soc_rt286 snd_soc_rl6347a snd_soc_core efivarfs
  CPU: 1 PID: 354 Comm: log2exe Not tainted 4.12.0-rc7-test-test #19
  Hardware name: Intel corporation NUC6CAYS/NUC6CAYB, BIOS AYAPLCEL.86A.0027.2016.1108.1529 11/08/2016
  Call Trace:
   bad_page+0x16a/0x1f0
   free_pages_check_bad+0x117/0x190
   free_hot_cold_page+0x7b1/0xad0
   __put_page+0x70/0xa0
   madvise_free_huge_pmd+0x627/0x7b0
   madvise_free_pte_range+0x6f8/0x1150
   __walk_page_range+0x6b5/0xe30
   walk_page_range+0x13b/0x310
   madvise_free_page_range.isra.16+0xad/0xd0
   madvise_free_single_vma+0x2e4/0x470
   SyS_madvise+0x8ce/0x1450

If somebody frees the page under us and we hold the last reference to
it, put_page() would attempt to free the page before unlocking it.

The fix is trivial reorder of operations.

Dave said:
 "I came up with the exact same patch.  For posterity, here's the test
  case, generated by syzkaller and trimmed down by Reinette:

  	https://www.sr71.net/~dave/intel/log2.c

  And the config that helps detect this:

  	https://www.sr71.net/~dave/intel/config-log2"

Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
Link: http://lkml.kernel.org/r/20170628101249.17879-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov 
Reported-by: Reinette Chatre 
Acked-by: Dave Hansen 
Acked-by: Michal Hocko 
Acked-by: Minchan Kim 
Cc: Huang Ying 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/vmalloc.c: huge-vmap: fail gracefully on unexpected huge vmap mappings

2017-07-05T12:40:28+00:00

commit 029c54b09599573015a5c18dbe59cbdf42742237 upstream.

Existing code that uses vmalloc_to_page() may assume that any address
for which is_vmalloc_addr() returns true may be passed into
vmalloc_to_page() to retrieve the associated struct page.

This is not un unreasonable assumption to make, but on architectures
that have CONFIG_HAVE_ARCH_HUGE_VMAP=y, it no longer holds, and we need
to ensure that vmalloc_to_page() does not go off into the weeds trying
to dereference huge PUDs or PMDs as table entries.

Given that vmalloc() and vmap() themselves never create huge mappings or
deal with compound pages at all, there is no correct answer in this
case, so return NULL instead, and issue a warning.

When reading /proc/kcore on arm64, you will hit an oops as soon as you
hit the huge mappings used for the various segments that make up the
mapping of vmlinux.  With this patch applied, you will no longer hit the
oops, but the kcore contents willl be incorrect (these regions will be
zeroed out)

We are fixing this for kcore specifically, so it avoids vread() for
those regions.  At least one other problematic user exists, i.e.,
/dev/kmem, but that is currently broken on arm64 for other reasons.

Link: http://lkml.kernel.org/r/20170609082226.26152-1-ard.biesheuvel@linaro.org
Signed-off-by: Ard Biesheuvel 
Acked-by: Mark Rutland 
Reviewed-by: Laura Abbott 
Cc: Michal Hocko 
Cc: zhong jiang 
Cc: Dave Hansen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[ardb: non-trivial backport to v4.9]
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Greg Kroah-Hartman

mm: numa: avoid waiting on freed migrated pages

2017-07-05T12:40:19+00:00

commit 3c226c637b69104f6b9f1c6ec5b08d7b741b3229 upstream.

In do_huge_pmd_numa_page(), we attempt to handle a migrating thp pmd by
waiting until the pmd is unlocked before we return and retry.  However,
we can race with migrate_misplaced_transhuge_page():

    // do_huge_pmd_numa_page                // migrate_misplaced_transhuge_page()
    // Holds 0 refs on page                 // Holds 2 refs on page

    vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
    /* ... */
    if (pmd_trans_migrating(*vmf->pmd)) {
            page = pmd_page(*vmf->pmd);
            spin_unlock(vmf->ptl);
                                            ptl = pmd_lock(mm, pmd);
                                            if (page_count(page) != 2)) {
                                                    /* roll back */
                                            }
                                            /* ... */
                                            mlock_migrate_page(new_page, page);
                                            /* ... */
                                            spin_unlock(ptl);
                                            put_page(page);
                                            put_page(page); // page freed here
            wait_on_page_locked(page);
            goto out;
    }

This can result in the freed page having its waiters flag set
unexpectedly, which trips the PAGE_FLAGS_CHECK_AT_PREP checks in the
page alloc/free functions.  This has been observed on arm64 KVM guests.

We can avoid this by having do_huge_pmd_numa_page() take a reference on
the page before dropping the pmd lock, mirroring what we do in
__migration_entry_wait().

When we hit the race, migrate_misplaced_transhuge_page() will see the
reference and abort the migration, as it may do today in other cases.

Fixes: b8916634b77bffb2 ("mm: Prevent parallel splits during THP migration")
Link: http://lkml.kernel.org/r/1497349722-6731-2-git-send-email-will.deacon@arm.com
Signed-off-by: Mark Rutland 
Signed-off-by: Will Deacon 
Acked-by: Steve Capper 
Acked-by: Kirill A. Shutemov 
Acked-by: Vlastimil Babka 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm, swap_cgroup: reschedule when neeed in swap_cgroup_swapoff()

2017-07-05T12:40:17+00:00

commit 460bcec84e11c75122ace5976214abbc596eb91b upstream.

We got need_resched() warnings in swap_cgroup_swapoff() because
swap_cgroup_ctrl[type].length is particularly large.

Reschedule when needed.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1704061315270.80559@chino.kir.corp.google.com
Signed-off-by: David Rientjes 
Acked-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: Vladimir Davydov 
Cc: KAMEZAWA Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Cc: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

mm: fix new crash in unmapped_area_topdown()

2017-06-24T05:11:18+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: Greg Kroah-Hartman