We currently have two related PMD vs PTE races in the DAX code.  These
can both be easily triggered by having two threads reading and writing
simultaneously to the same private mapping, with the key being that
private mapping reads can be handled with PMDs but private mapping
writes are always handled with PTEs so that we can COW.

Here is the first race:

  CPU 0					CPU 1

  (private mapping write)
  __handle_mm_fault()
    create_huge_pmd() - FALLBACK
    handle_pte_fault()
      passes check for pmd_devmap()

					(private mapping read)
					__handle_mm_fault()
					  create_huge_pmd()
					    dax_iomap_pmd_fault() inserts PMD

      dax_iomap_pte_fault() does a PTE fault, but we already have a DAX PMD
      			  installed in our page tables at this spot.

Here's the second race:

  CPU 0					CPU 1

  (private mapping read)
  __handle_mm_fault()
    passes check for pmd_none()
    create_huge_pmd()
      dax_iomap_pmd_fault() inserts PMD

  (private mapping write)
  __handle_mm_fault()
    create_huge_pmd() - FALLBACK
					(private mapping read)
					__handle_mm_fault()
					  passes check for pmd_none()
					  create_huge_pmd()

    handle_pte_fault()
      dax_iomap_pte_fault() inserts PTE
					    dax_iomap_pmd_fault() inserts PMD,
					       but we already have a PTE at
					       this spot.

The core of the issue is that while there is isolation between faults to
the same range in the DAX fault handlers via our DAX entry locking,
there is no isolation between faults in the code in mm/memory.c.  This
means for instance that this code in __handle_mm_fault() can run:

	if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) {
		ret = create_huge_pmd(&vmf);

But by the time we actually get to run the fault handler called by
create_huge_pmd(), the PMD is no longer pmd_none() because a racing PTE
fault has installed a normal PMD here as a parent.  This is the cause of
the 2nd race.  The first race is similar - there is the following check
in handle_pte_fault():

	} else {
		/* See comment in pte_alloc_one_map() */
		if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd))
			return 0;

So if a pmd_devmap() PMD (a DAX PMD) has been installed at vmf->pmd, we
will bail and retry the fault.  This is correct, but there is nothing
preventing the PMD from being installed after this check but before we
actually get to the DAX PTE fault handlers.

In my testing these races result in the following types of errors:

  BUG: Bad rss-counter state mm:ffff8800a817d280 idx:1 val:1
  BUG: non-zero nr_ptes on freeing mm: 15

Fix this issue by having the DAX fault handlers verify that it is safe
to continue their fault after they have taken an entry lock to block
other racing faults.

[ross.zwisler@linux.intel.com: improve fix for colliding PMD & PTE entries]
  Link: http://lkml.kernel.org/r/20170526195932.32178-1-ross.zwisler@linux.intel.com
Link: http://lkml.kernel.org/r/20170522215749.23516-2-ross.zwisler@linux.intel.comSigned-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Pawel Lebioda <pawel.lebioda@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Pawel Lebioda <pawel.lebioda@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Xiong Zhou <xzhou@redhat.com>
Cc: Eryu Guan <eguan@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When the pmd_devmap() checks were added by 5c7fb56e ("mm, dax:
dax-pmd vs thp-pmd vs hugetlbfs-pmd") to add better support for DAX huge
pages, they were all added to the end of if() statements after existing
pmd_trans_huge() checks.  So, things like:

  -       if (pmd_trans_huge(*pmd))
  +       if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd))

When further checks were added after pmd_trans_unstable() checks by
commit 7267ec00 ("mm: postpone page table allocation until we have
page to map") they were also added at the end of the conditional:

  +       if (pmd_trans_unstable(fe->pmd) || pmd_devmap(*fe->pmd))

This ordering is fine for pmd_trans_huge(), but doesn't work for
pmd_trans_unstable().  This is because DAX huge pages trip the bad_pmd()
check inside of pmd_none_or_trans_huge_or_clear_bad() (called by
pmd_trans_unstable()), which prints out a warning and returns 1.  So, we
do end up doing the right thing, but only after spamming dmesg with
suspicious looking messages:

  mm/pgtable-generic.c:39: bad pmd ffff8808daa49b88(84000001006000a5)

Reorder these checks in a helper so that pmd_devmap() is checked first,
avoiding the error messages, and add a comment explaining why the
ordering is important.

Fixes: commit 7267ec00 ("mm: postpone page table allocation until we have page to map")
Link: http://lkml.kernel.org/r/20170522215749.23516-1-ross.zwisler@linux.intel.comSigned-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Pawel Lebioda <pawel.lebioda@intel.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Xiong Zhou <xzhou@redhat.com>
Cc: Eryu Guan <eguan@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Roman Gushchin has reported that the OOM killer can trivially selects
next OOM victim when a thread doing memory allocation from page fault
path was selected as first OOM victim.

    allocate invoked oom-killer: gfp_mask=0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null),  order=0, oom_score_adj=0
    allocate cpuset=/ mems_allowed=0
    CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
    Call Trace:
     oom_kill_process+0x219/0x3e0
     out_of_memory+0x11d/0x480
     __alloc_pages_slowpath+0xc84/0xd40
     __alloc_pages_nodemask+0x245/0x260
     alloc_pages_vma+0xa2/0x270
     __handle_mm_fault+0xca9/0x10c0
     handle_mm_fault+0xf3/0x210
     __do_page_fault+0x240/0x4e0
     trace_do_page_fault+0x37/0xe0
     do_async_page_fault+0x19/0x70
     async_page_fault+0x28/0x30
    ...
    Out of memory: Kill process 492 (allocate) score 899 or sacrifice child
    Killed process 492 (allocate) total-vm:2052368kB, anon-rss:1894576kB, file-rss:4kB, shmem-rss:0kB
    allocate: page allocation failure: order:0, mode:0x14280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=(null)
    allocate cpuset=/ mems_allowed=0
    CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
    Call Trace:
     __alloc_pages_slowpath+0xd32/0xd40
     __alloc_pages_nodemask+0x245/0x260
     alloc_pages_vma+0xa2/0x270
     __handle_mm_fault+0xca9/0x10c0
     handle_mm_fault+0xf3/0x210
     __do_page_fault+0x240/0x4e0
     trace_do_page_fault+0x37/0xe0
     do_async_page_fault+0x19/0x70
     async_page_fault+0x28/0x30
    ...
    oom_reaper: reaped process 492 (allocate), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
    ...
    allocate invoked oom-killer: gfp_mask=0x0(), nodemask=(null),  order=0, oom_score_adj=0
    allocate cpuset=/ mems_allowed=0
    CPU: 1 PID: 492 Comm: allocate Not tainted 4.12.0-rc1-mm1+ #181
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
    Call Trace:
     oom_kill_process+0x219/0x3e0
     out_of_memory+0x11d/0x480
     pagefault_out_of_memory+0x68/0x80
     mm_fault_error+0x8f/0x190
     ? handle_mm_fault+0xf3/0x210
     __do_page_fault+0x4b2/0x4e0
     trace_do_page_fault+0x37/0xe0
     do_async_page_fault+0x19/0x70
     async_page_fault+0x28/0x30
    ...
    Out of memory: Kill process 233 (firewalld) score 10 or sacrifice child
    Killed process 233 (firewalld) total-vm:246076kB, anon-rss:20956kB, file-rss:0kB, shmem-rss:0kB

There is a race window that the OOM reaper completes reclaiming the
first victim's memory while nothing but mutex_trylock() prevents the
first victim from calling out_of_memory() from pagefault_out_of_memory()
after memory allocation for page fault path failed due to being selected
as an OOM victim.

This is a side effect of commit 9a67f648 ("mm: consolidate
GFP_NOFAIL checks in the allocator slowpath") because that commit
silently changed the behavior from

    /* Avoid allocations with no watermarks from looping endlessly */

to

    /*
     * Give up allocations without trying memory reserves if selected
     * as an OOM victim
     */

in __alloc_pages_slowpath() by moving the location to check TIF_MEMDIE
flag.  I have noticed this change but I didn't post a patch because I
thought it is an acceptable change other than noise by warn_alloc()
because !__GFP_NOFAIL allocations are allowed to fail.  But we
overlooked that failing memory allocation from page fault path makes
difference due to the race window explained above.

While it might be possible to add a check to pagefault_out_of_memory()
that prevents the first victim from calling out_of_memory() or remove
out_of_memory() from pagefault_out_of_memory(), changing
pagefault_out_of_memory() does not suppress noise by warn_alloc() when
allocating thread was selected as an OOM victim.  There is little point
with printing similar backtraces and memory information from both
out_of_memory() and warn_alloc().

Instead, if we guarantee that current thread can try allocations with no
watermarks once when current thread looping inside
__alloc_pages_slowpath() was selected as an OOM victim, we can follow "who
can use memory reserves" rules and suppress noise by warn_alloc() and
prevent memory allocations from page fault path from calling
pagefault_out_of_memory().

If we take the comment literally, this patch would do

  -    if (test_thread_flag(TIF_MEMDIE))
  -        goto nopage;
  +    if (alloc_flags == ALLOC_NO_WATERMARKS || (gfp_mask & __GFP_NOMEMALLOC))
  +        goto nopage;

because gfp_pfmemalloc_allowed() returns false if __GFP_NOMEMALLOC is
given.  But if I recall correctly (I couldn't find the message), the
condition is meant to apply to only OOM victims despite the comment.
Therefore, this patch preserves TIF_MEMDIE check.

Fixes: 9a67f648 ("mm: consolidate GFP_NOFAIL checks in the allocator slowpath")
Link: http://lkml.kernel.org/r/201705192112.IAF69238.OQOHSJLFOFFMtV@I-love.SAKURA.ne.jpSigned-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Roman Gushchin <guro@fb.com>
Tested-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <stable@vger.kernel.org>	[4.11]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 5b5e0928 ("lib/vsprintf.c: remove %Z support") removed some
usages of format %Z but forgot "%.2Zx".  This makes clang 4.0 reports a
-Wformat-extra-args warning because it does not know about %Z.

Replace %Z with %z.

Link: http://lkml.kernel.org/r/20170520090946.22562-1-nicolas.iooss_linux@m4x.orgSigned-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Harald Welte <laforge@gnumonks.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <stable@vger.kernel.org>	[4.11+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

memcg_propagate_slab_attrs() abuses the sysfs attribute file functions
to propagate settings from the root kmem_cache to a newly created
kmem_cache.  It does that with:

     attr->show(root, buf);
     attr->store(new, buf, strlen(bug);

Aside of being a lazy and absurd hackery this is broken because it does
not check the return value of the show() function.

Some of the show() functions return 0 w/o touching the buffer.  That
means in such a case the store function is called with the stale content
of the previous show().  That causes nonsense like invoking
kmem_cache_shrink() on a newly created kmem_cache.  In the worst case it
would cause handing in an uninitialized buffer.

This should be rewritten proper by adding a propagate() callback to
those slub_attributes which must be propagated and avoid that insane
conversion to and from ASCII, but that's too large for a hot fix.

Check at least the return value of the show() function, so calling
store() with stale content is prevented.

Steven said:
 "It can cause a deadlock with get_online_cpus() that has been uncovered
  by recent cpu hotplug and lockdep changes that Thomas and Peter have
  been doing.

     Possible unsafe locking scenario:

           CPU0                    CPU1
           ----                    ----
      lock(cpu_hotplug.lock);
                                   lock(slab_mutex);
                                   lock(cpu_hotplug.lock);
      lock(slab_mutex);

     *** DEADLOCK ***"

Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1705201244540.2255@nanosSigned-off-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit db2aa7fd ("initramfs: allow again choice of the embedded
initram compression algorithm") introduced the possibility to select the
initramfs compression algorithm from Kconfig and while this is a nice
feature it broke the use case described below.

Here is what my build system does:

 - kernel is initially configured not to have an initramfs included

 - build the user space root file system

 - re-configure the kernel to have an initramfs included
   (CONFIG_INITRAMFS_SOURCE="/path/to/romfs") and set relevant
   CONFIG_INITRAMFS options, in my case, no compression option
   (CONFIG_INITRAMFS_COMPRESSION_NONE)

 - kernel is re-built with these options -> kernel+initramfs image is
   copied

 - kernel is re-built again without these options -> kernel image is
   copied

Building a kernel without an initramfs means setting this option:

  CONFIG_INITRAMFS_SOURCE="" (and this one only)

whereas building a kernel with an initramfs means setting these options:

  CONFIG_INITRAMFS_SOURCE="/home/fainelli/work/uclinux-rootfs/romfs /home/fainelli/work/uclinux-rootfs/misc/initramfs.dev"
  CONFIG_INITRAMFS_ROOT_UID=1000
  CONFIG_INITRAMFS_ROOT_GID=1000
  CONFIG_INITRAMFS_COMPRESSION_NONE=y
  CONFIG_INITRAMFS_COMPRESSION=""

Commit db2aa7fd ("initramfs: allow again choice of the embedded
initram compression algorithm") is problematic because
CONFIG_INITRAMFS_COMPRESSION which is used to determine the
initramfs_data.cpio extension/compression is a string, and due to how
Kconfig works it will evaluate in order, how to assign it.

Setting CONFIG_INITRAMFS_COMPRESSION_NONE with CONFIG_INITRAMFS_SOURCE=""
cannot possibly work (because of the depends on INITRAMFS_SOURCE!=""
imposed on CONFIG_INITRAMFS_COMPRESSION ) yet we still get
CONFIG_INITRAMFS_COMPRESSION assigned to ".gz" because CONFIG_RD_GZIP=y
is set in my kernel, even when there is no initramfs being built.

So we basically end-up generating two initramfs_data.cpio* files, one
without extension, and one with .gz.  This causes usr/Makefile to track
usr/initramfs_data.cpio.gz, and not usr/initramfs_data.cpio anymore,
that is also largely problematic after 9e3596b0 ("kbuild:
initramfs cleanup, set target from Kconfig") because we used to track
all possible initramfs_data files in the $(targets) variable before that
commit.

The end result is that the kernel with an initramfs clearly does not
contain what we expect it to, it has a stale initramfs_data.cpio file
built into it, and we keep re-generating an initramfs_data.cpio.gz file
which is not the one that we want to include in the kernel image proper.

The fix consists in hiding CONFIG_INITRAMFS_COMPRESSION when
CONFIG_INITRAMFS_SOURCE="".  This puts us back in a state to the
pre-4.10 behavior where we can properly disable and re-enable initramfs
within the same kernel .config file, and be in control of what
CONFIG_INITRAMFS_COMPRESSION is set to.

Fixes: db2aa7fd ("initramfs: allow again choice of the embedded initram compression algorithm")
Fixes: 9e3596b0 ("kbuild: initramfs cleanup, set target from Kconfig")
Link: http://lkml.kernel.org/r/20170521033337.6197-1-f.fainelli@gmail.comSigned-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Cc: P J P <ppandit@redhat.com>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

While converting drm_[cm]alloc* helpers to kvmalloc* variants Chris
Wilson has wondered why we want to try kmalloc before vmalloc fallback
even for larger allocations requests.  Let's clarify that one larger
physically contiguous block is less likely to fragment memory than many
scattered pages which can prevent more large blocks from being created.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170517080932.21423-1-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 7c30f352 ("jiffies.h: declare jiffies and jiffies_64 with
____cacheline_aligned_in_smp") removed a section specification from the
jiffies declaration that caused conflicts on some platforms.

Unfortunately this change broke the build for frv:

  kernel/built-in.o: In function `__do_softirq': (.text+0x6460): relocation truncated to fit: R_FRV_GPREL12 against symbol
      `jiffies' defined in *ABS* section in .tmp_vmlinux1
  kernel/built-in.o: In function `__do_softirq': (.text+0x6574): relocation truncated to fit: R_FRV_GPREL12 against symbol
      `jiffies' defined in *ABS* section in .tmp_vmlinux1
  kernel/built-in.o: In function `pwq_activate_delayed_work': workqueue.c:(.text+0x15b9c): relocation truncated to fit: R_FRV_GPREL12 against
      symbol `jiffies' defined in *ABS* section in .tmp_vmlinux1
  ...

Add __jiffy_arch_data to the declaration of jiffies and use it on frv to
include the section specification.  For all other platforms
__jiffy_arch_data (currently) has no effect.

Fixes: 7c30f352 ("jiffies.h: declare jiffies and jiffies_64 with ____cacheline_aligned_in_smp")
Link: http://lkml.kernel.org/r/20170516221333.177280-1-mka@chromium.orgSigned-off-by: Matthias Kaehlcke <mka@chromium.org>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Igor Stoppa has noticed that __GFP_NOLOCKDEP can use a lower bit.  At
the time commit 7e784422 ("lockdep: allow to disable reclaim lockup
detection") was written we still had __GFP_OTHER_NODE but I have removed
it in commit 41b6167e ("mm: get rid of __GFP_OTHER_NODE") and forgot
to lower the bit value.

The current value is outside of __GFP_BITS_SHIFT so it cannot be used
actually.

Fixes: 7e784422 ("lockdep: allow to disable reclaim lockup detection")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Igor Stoppa <igor.stoppa@nokia.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

"err" needs to be left set to -EFAULT if split_huge_page succeeds.
Otherwise if "err" gets clobbered with zero and write_protect_page
fails, try_to_merge_one_page() will succeed instead of returning -EFAULT
and then try_to_merge_with_ksm_page() will continue thinking kpage is a
PageKsm when in fact it's still an anonymous page.  Eventually it'll
crash in page_add_anon_rmap.

This has been reproduced on Fedora25 kernel but I can reproduce with
upstream too.

The bug was introduced in commit f765f540 ("ksm: prepare to new THP
semantics") introduced in v4.5.

    page:fffff67546ce1cc0 count:4 mapcount:2 mapping:ffffa094551e36e1 index:0x7f0f46673
    flags: 0x2ffffc0004007c(referenced|uptodate|dirty|lru|active|swapbacked)
    page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
    page->mem_cgroup:ffffa09674bf0000
    ------------[ cut here ]------------
    kernel BUG at mm/rmap.c:1222!
    CPU: 1 PID: 76 Comm: ksmd Not tainted 4.9.3-200.fc25.x86_64 #1
    RIP: do_page_add_anon_rmap+0x1c4/0x240
    Call Trace:
      page_add_anon_rmap+0x18/0x20
      try_to_merge_with_ksm_page+0x50b/0x780
      ksm_scan_thread+0x1211/0x1410
      ? prepare_to_wait_event+0x100/0x100
      ? try_to_merge_with_ksm_page+0x780/0x780
      kthread+0xd9/0xf0
      ? kthread_park+0x60/0x60
      ret_from_fork+0x25/0x30

Fixes: f765f540 ("ksm: prepare to new THP semantics")
Link: http://lkml.kernel.org/r/20170513131040.21732-1-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Federico Simoncelli <fsimonce@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull sound fixes from Takashi Iwai:
 "This contains the fixes for a few reported regression for HD-audio and
  USB-audio. All small, trivial, and boring"

* tag 'sound-4.12-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: hda - Fix applying MSI dual-codec mobo quirk
  ALSA: usb: Avoid VLA in mixer_us16x08.c
  ALSA: usb: Fix a typo in Tascam US-16x08 mixer element
  Revert "ALSA: usb-audio: purge needless variable length array"

Pull dmaengine fixes from Vinod Koul:
 "Here is the dmaengine fixes request for 4.12. Fixes bunch of issues in
  the driver, npthing exciting though..

   - mv_xor_v2 driver fixes for handling descriptors, tx_submit
     implementation, removing interrupt coalescing and setting DMA mask
     properly

   - fix usb-dmac DMAOR AE bit definition

   - fix ep93xx start buffer from BASE0 and not drain the transfers in
     terminate_all

   - fix rcar-dmac to use right descriptor pointer for residue
     calculation

   - pl330 fix warn for irq freeup"

* tag 'dmaengine-fix-4.12-rc4' of git://git.infradead.org/users/vkoul/slave-dma:
  dmaengine: pl330: fix warning in pl330_remove
  rcar-dmac: fixup descriptor pointer for descriptor mode
  dmaengine: ep93xx: Don't drain the transfers in terminate_all()
  dmaengine: ep93xx: Always start from BASE0
  dmaengine: usb-dmac: Fix DMAOR AE bit definition
  dmaengine: mv_xor_v2: set DMA mask to 40 bits
  dmaengine: mv_xor_v2: remove interrupt coalescing
  dmaengine: mv_xor_v2: fix tx_submit() implementation
  dmaengine: mv_xor_v2: enable XOR engine after its configuration
  dmaengine: mv_xor_v2: do not use descriptors not acked by async_tx
  dmaengine: mv_xor_v2: properly handle wrapping in the array of HW descriptors
  dmaengine: mv_xor_v2: handle mv_xor_v2_prep_sw_desc() error properly

Pull HID fixes from Jiri Kosina:

 - corner-case oops fixes for Asus and Wacom drivers from Carlo Caione
   and Jason Gerecke

 - power management fix (reported on SIS0817 touchscreen) for i2c-hid
   devices from Hans de Goede

 - device-id-specific fixes and quirks from Hans de Goede, Diego Elio
   Pettenò and Che-Liang Chiou

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid:
  HID: asus: Stop underlying hardware on remove
  HID: i2c: Call acpi_device_fix_up_power for ACPI-enumerated devices
  HID: asus: Add support for T100 keyboard
  HID: elecom: extend to fix the descriptor for DEFT trackballs
  HID: magicmouse: Set multi-touch keybits for Magic Mouse
  HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference

Pull livepatching fix from Jiri Kosina:
 "Kconfig dependency fix for livepatching infrastructure from Miroslav
  Benes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching:
  livepatch: Make livepatch dependent on !TRIM_UNUSED_KSYMS

Pull x86 fixes from Ingo Molnar:
 "Misc fixes:

   - revert a broken PAT commit that broke a number of systems

   - fix two preemptability warnings/bugs that can trigger under certain
     circumstances, in the debug code and in the microcode loader"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Revert "x86/PAT: Fix Xorg regression on CPUs that don't support PAT"
  x86/debug/32: Convert a smp_processor_id() call to raw to avoid DEBUG_PREEMPT warning
  x86/microcode/AMD: Change load_microcode_amd()'s param to bool to fix preemptibility bug

Pull EFI fixes from Ingo Molnar:
 "Misc fixes:

   - three boot crash fixes for uncommon configurations

   - silence a boot warning under virtualization

   - plus a GCC 7 related (harmless) build warning fix"

* 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efi/bgrt: Skip efi_bgrt_init() in case of non-EFI boot
  x86/efi: Correct EFI identity mapping under 'efi=old_map' when KASLR is enabled
  x86/efi: Disable runtime services on kexec kernel if booted with efi=old_map
  efi: Remove duplicate 'const' specifiers
  efi: Don't issue error message when booted under Xen

We are missing a call to hid_hw_stop() on the remove hook.
Among other things this is causing an Oops when (re-)starting GNOME /
upowerd / ... after the module has been already rmmod-ed.
Signed-off-by: Carlo Caione <carlo@endlessm.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

When removing a device with less than 9 IRQs (AMBA_NR_IRQS), we'll get a
big WARN_ON from devres.c because pl330_remove calls devm_free_irqs for
unallocated irqs. Similarly to pl330_probe, check that IRQ number is
present before calling devm_free_irq.
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

Pull nfsd fixes from Bruce Fields:
 "Revert patch accidentally included in the merge window pull request,
  and fix a crash that was likely a result of buggy client behavior"

* tag 'nfsd-4.12-1' of git://linux-nfs.org/~bfields/linux:
  nfsd4: fix null dereference on replay
  nfsd: Revert "nfsd: check for oversized NFSv2/v3 arguments"

Pull gcc-plugin prepwork from Kees Cook:
 "Use designated initializers for mtk-vcodec, powerplay, amdgpu, and
  sgi-xp. Use ERR_CAST() to avoid cross-structure cast in ocf2, ntfs,
  and NFS.

  Christoph Hellwig recommended that I send these fixes now, rather than
  waiting for the v4.13 merge window. These are all initializer and cast
  fixes needed for the future randstruct plugin that haven't been picked
  up by the respective maintainers"

* tag 'gcc-plugins-v4.12-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  mtk-vcodec: Use designated initializers
  drm/amd/powerplay: Use designated initializers
  drm/amdgpu: Use designated initializers
  sgi-xp: Use designated initializers
  ocfs2: Use ERR_CAST() to avoid cross-structure cast
  ntfs: Use ERR_CAST() to avoid cross-structure cast
  NFS: Use ERR_CAST() to avoid cross-structure cast

Pull KVM fixes from Paolo Bonzini:
 "Many small x86 bug fixes: SVM segment registers access rights, nested
  VMX, preempt notifiers, LAPIC virtual wire mode, NMI injection"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: x86: Fix nmi injection failure when vcpu got blocked
  KVM: SVM: do not zero out segment attributes if segment is unusable or not present
  KVM: SVM: ignore type when setting segment registers
  KVM: nVMX: fix nested_vmx_check_vmptr failure paths under debugging
  KVM: x86: Fix virtual wire mode
  KVM: nVMX: Fix handling of lmsw instruction
  KVM: X86: Fix preempt the preemption timer cancel

Pull Reiserfs and GFS2 fixes from Jan Kara:
 "Fixes to GFS2 & Reiserfs for the fallout of the recent WRITE_FUA
  cleanup from Christoph.

  Fixes for other filesystems were already merged by respective
  maintainers."

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  reiserfs: Make flush bios explicitely sync
  gfs2: Make flush bios explicitely sync

Pull SCSI target fixes from Nicholas Bellinger:
 "Here are the target-pending fixes for v4.12-rc4:

   - ibmviscsis ABORT_TASK handling fixes that missed the v4.12 merge
     window. (Bryant Ly and Michael Cyr)

   - Re-add a target-core check enforcing WRITE overflow reject that was
     relaxed in v4.3, to avoid unsupported iscsi-target immediate data
     overflow. (nab)

   - Fix a target-core-user OOPs during device removal. (MNC + Bryant
     Ly)

   - Fix a long standing iscsi-target potential issue where kthread exit
     did not wait for kthread_should_stop(). (Jiang Yi)

   - Fix a iscsi-target v3.12.y regression OOPs involving initial login
     PDU processing during asynchronous TCP connection close. (MNC +
     nab)

  This is a little larger than usual for an -rc4, primarily due to the
  iscsi-target v3.12.y regression OOPs bug-fix.

  However, it's an important patch as MNC + Hannes where both able to
  trigger it using a reduced iscsi initiator login timeout combined with
  a backend taking a long time to complete I/Os during iscsi login
  driven session reinstatement"

* git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending:
  iscsi-target: Always wait for kthread_should_stop() before kthread exit
  iscsi-target: Fix initial login PDU asynchronous socket close OOPs
  tcmu: fix crash during device removal
  target: Re-add check to reject control WRITEs with overflow data
  ibmvscsis: Fix the incorrect req_lim_delta
  ibmvscsis: Clear left-over abort_cmd pointers

This reverts commit cbed27cd.

As Andy Lutomirski observed:

 "I think this patch is bogus. pat_enabled() sure looks like it's
  supposed to return true if PAT is *enabled*, and these days PAT is
  'enabled' even if there's no HW PAT support."
Reported-by: Bernhard Held <berny156@gmx.de>
Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: stable@vger.kernel.org # v4.2+
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

When spin_lock_irqsave() deadlock occurs inside the guest, vcpu threads,
other than the lock-holding one, would enter into S state because of
pvspinlock. Then inject NMI via libvirt API "inject-nmi", the NMI could
not be injected into vm.

The reason is:
1 It sets nmi_queued to 1 when calling ioctl KVM_NMI in qemu, and sets
cpu->kvm_vcpu_dirty to true in do_inject_external_nmi() meanwhile.
2 It sets nmi_queued to 0 in process_nmi(), before entering guest, because
cpu->kvm_vcpu_dirty is true.

It's not enough just to check nmi_queued to decide whether to stay in
vcpu_block() or not. NMI should be injected immediately at any situation.
Add checking nmi_pending, and testing KVM_REQ_NMI replaces nmi_queued
in vm_vcpu_has_events().

Do the same change for SMIs.
Signed-off-by: Zhuang Yanying <ann.zhuangyanying@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

This is a fix for the problem [1], where VMCB.CPL was set to 0 and interrupt
was taken on userspace stack.  The root cause lies in the specific AMD CPU
behaviour which manifests itself as unusable segment attributes on SYSRET.
The corresponding work around for the kernel is the following:

61f01dd9 ("x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue")

In other turn virtualization side treated unusable segment incorrectly and
restored CPL from SS attributes, which were zeroed out few lines above.

In current patch it is assured only that P bit is cleared in VMCB.save state
and segment attributes are not zeroed out if segment is not presented or is
unusable, therefore CPL can be safely restored from DPL field.

This is only one part of the fix, since QEMU side should be fixed accordingly
not to zero out attributes on its side.  Corresponding patch will follow.

[1] Message id: CAJrWOzD6Xq==b-zYCDdFLgSRMPM-NkNuTSDFEtX=7MreT45i7Q@mail.gmail.com
Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com>
Signed-off-by: Mikhail Sennikovskii <mikhail.sennikovskii@profitbricks.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim KrÄmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

The previous commit [63691587: ALSA: hda - Apply dual-codec quirk
for MSI Z270-Gaming mobo] attempted to apply the existing dual-codec
quirk for a MSI mobo.  But it turned out that this isn't applied
properly due to the MSI-vendor quirk before this entry.  I overlooked
such two MSI entries just because they were put in the wrong position,
although we have a list ordered by PCI SSID numbers.

This patch fixes it by rearranging the unordered entries.

Fixes: 63691587 ("ALSA: hda - Apply dual-codec quirk for MSI Z270-Gaming mobo")
Reported-by: Rudolf Schmidt <info@rudolfschmidt.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Pull drm fixes from Dave Airlie:
 "This is the main set of fixes for rc4, one amdgpu fix, some exynos
  regression fixes, some msm fixes and some i915 and GVT fixes.

  I've got a second regression fix for some DP chips that might be a
  bit large, but I think we'd like to land it now, I'll send it along
  tomorrow, once you are happy with this set"

* tag 'drm-fixes-for-v4.12-rc4' of git://people.freedesktop.org/~airlied/linux: (24 commits)
  drm/amdgpu: Program ring for vce instance 1 at its register space
  drm/exynos: clean up description of exynos_drm_crtc
  drm/exynos: dsi: Remove bridge node reference in removal
  drm/exynos: dsi: Fix the parse_dt function
  drm/exynos: Merge pre/postclose hooks
  drm/msm: Fix the check for the command size
  drm/msm: Take the mutex before calling msm_gem_new_impl
  drm/msm: for array in-fences, check if all backing fences are from our own context before waiting
  drm/msm: constify irq_domain_ops
  drm/msm/mdp5: release hwpipe(s) for unused planes
  drm/msm: Reuse dma_fence_release.
  drm/msm: Expose our reservation object when exporting a dmabuf.
  drm/msm/gpu: check legacy clk names in get_clocks()
  drm/msm/mdp5: use __drm_atomic_helper_plane_duplicate_state()
  drm/msm: select PM_OPP
  drm/i915: Stop pretending to mask/unmask LPE audio interrupts
  drm/i915/selftests: Silence compiler warning in igt_ctx_exec
  Revert "drm/i915: Restore lost "Initialized i915" welcome message"
  drm/i915/gvt: clean up unsubmited workloads before destroying kmem cache
  drm/i915/gvt: Disable compression workaround for Gen9
  ...

Merge tag 'exynos-drm-fixes-for-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos into drm-fixes

- Fix a regression to description of exynos_drm_crtc
- Remove preclose hook of Exynos
  . This was a exynos change of the patch series[1] merged already.
- Fix one dt broken issue
- Make sure to release bridge_node of Exynos MIPI-DSI driver.

[1] https://lists.freedesktop.org/archives/dri-devel/2017-March/135111.html

* tag 'exynos-drm-fixes-for-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos:
  drm/exynos: clean up description of exynos_drm_crtc
  drm/exynos: dsi: Remove bridge node reference in removal
  drm/exynos: dsi: Fix the parse_dt function
  drm/exynos: Merge pre/postclose hooks

* 'drm-fixes-4.12' of git://people.freedesktop.org/~agd5f/linux:
  drm/amdgpu: Program ring for vce instance 1 at its register space

a few fixes for 4.12..

* 'msm-fixes-4.12-rc4' of git://people.freedesktop.org/~robclark/linux:
  drm/msm: Fix the check for the command size
  drm/msm: Take the mutex before calling msm_gem_new_impl
  drm/msm: for array in-fences, check if all backing fences are from our own context before waiting
  drm/msm: constify irq_domain_ops
  drm/msm/mdp5: release hwpipe(s) for unused planes
  drm/msm: Reuse dma_fence_release.
  drm/msm: Expose our reservation object when exporting a dmabuf.
  drm/msm/gpu: check legacy clk names in get_clocks()
  drm/msm/mdp5: use __drm_atomic_helper_plane_duplicate_state()
  drm/msm: select PM_OPP

Merge tag 'drm-intel-fixes-2017-05-29' of git://anongit.freedesktop.org/git/drm-intel into drm-fixes

drm/i915 fixes for v4.12-rc4

* tag 'drm-intel-fixes-2017-05-29' of git://anongit.freedesktop.org/git/drm-intel:
  drm/i915: Stop pretending to mask/unmask LPE audio interrupts
  drm/i915/selftests: Silence compiler warning in igt_ctx_exec
  Revert "drm/i915: Restore lost "Initialized i915" welcome message"
  drm/i915/gvt: clean up unsubmited workloads before destroying kmem cache
  drm/i915/gvt: Disable compression workaround for Gen9
  drm/i915: set initialised only when init_context callback is NULL
  drm/i915: Fix new -Wint-in-bool-context gcc compiler warning
  drm/i915: use vma->size for appgtt allocate_va_range
  drm/i915: Do not sync RCU during shrinking

There are three timing problems in the kthread usages of iscsi_target_mod:

 - np_thread of struct iscsi_np
 - rx_thread and tx_thread of struct iscsi_conn

In iscsit_close_connection(), it calls

 send_sig(SIGINT, conn->tx_thread, 1);
 kthread_stop(conn->tx_thread);

In conn->tx_thread, which is iscsi_target_tx_thread(), when it receive
SIGINT the kthread will exit without checking the return value of
kthread_should_stop().

So if iscsi_target_tx_thread() exit right between send_sig(SIGINT...)
and kthread_stop(...), the kthread_stop() will try to stop an already
stopped kthread.

This is invalid according to the documentation of kthread_stop().

(Fix -ECONNRESET logout handling in iscsi_target_tx_thread and
 early iscsi_target_rx_thread failure case - nab)
Signed-off-by: Jiang Yi <jiangyilism@gmail.com>
Cc: <stable@vger.kernel.org> # v3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

This patch fixes a OOPs originally introduced by:

   commit bb048357
   Author: Nicholas Bellinger <nab@linux-iscsi.org>
   Date:   Thu Sep 5 14:54:04 2013 -0700

   iscsi-target: Add sk->sk_state_change to cleanup after TCP failure

which would trigger a NULL pointer dereference when a TCP connection
was closed asynchronously via iscsi_target_sk_state_change(), but only
when the initial PDU processing in iscsi_target_do_login() from iscsi_np
process context was blocked waiting for backend I/O to complete.

To address this issue, this patch makes the following changes.

First, it introduces some common helper functions used for checking
socket closing state, checking login_flags, and atomically checking
socket closing state + setting login_flags.

Second, it introduces a LOGIN_FLAGS_INITIAL_PDU bit to know when a TCP
connection has dropped via iscsi_target_sk_state_change(), but the
initial PDU processing within iscsi_target_do_login() in iscsi_np
context is still running.  For this case, it sets LOGIN_FLAGS_CLOSED,
but doesn't invoke schedule_delayed_work().

The original NULL pointer dereference case reported by MNC is now handled
by iscsi_target_do_login() doing a iscsi_target_sk_check_close() before
transitioning to FFP to determine when the socket has already closed,
or iscsi_target_start_negotiation() if the login needs to exchange
more PDUs (eg: iscsi_target_do_login returned 0) but the socket has
closed.  For both of these cases, the cleanup up of remaining connection
resources will occur in iscsi_target_start_negotiation() from iscsi_np
process context once the failure is detected.

Finally, to handle to case where iscsi_target_sk_state_change() is
called after the initial PDU procesing is complete, it now invokes
conn->login_work -> iscsi_target_do_login_rx() to perform cleanup once
existing iscsi_target_sk_check_close() checks detect connection failure.
For this case, the cleanup of remaining connection resources will occur
in iscsi_target_do_login_rx() from delayed workqueue process context
once the failure is detected.
Reported-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Tested-by: Mike Christie <mchristi@redhat.com>
Cc: Mike Christie <mchristi@redhat.com>
Reported-by: Hannes Reinecke <hare@suse.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Varun Prakash <varun@chelsio.com>
Cc: <stable@vger.kernel.org> # v3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

We need program ring buffer on instance 1 register space domain,
when only if instance 1 available, with two instances or instance 0,
and we need only program instance 0 regsiter space domain for ring.
Signed-off-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Pull overlayfs fixes from Miklos Szeredi:
 "Fix regressions:

   - missing CONFIG_EXPORTFS dependency

   - failure if upper fs doesn't support xattr

   - bad error cleanup

  This also adds the concept of "impure" directories complementing the
  "origin" marking introduced in -rc1. Together they enable getting
  consistent st_ino and d_ino for directory listings.

  And there's a bug fix and a cleanup as well"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: filter trusted xattr for non-admin
  ovl: mark upper merge dir with type origin entries "impure"
  ovl: mark upper dir with type origin entries "impure"
  ovl: remove unused arg from ovl_lookup_temp()
  ovl: handle rename when upper doesn't support xattr
  ovl: don't fail copy-up if upper doesn't support xattr
  ovl: check on mount time if upper fs supports setting xattr
  ovl: fix creds leak in copy up error path
  ovl: select EXPORTFS

This is another attempt to work around the VLA used in
mixer_us16x08.c.  Basically the temporary array is used individually
for two cases, and we can declare locally in each block, instead of
hackish max() usage.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

A mixer element created in a quirk for Tascam US-16x08 contains a
typo: it should be "EQ MidLow Q" instead of "EQ MidQLow Q".

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195875
Fixes: d2bb390a ("ALSA: usb-audio: Tascam US-16x08 DSP mixer quirk")
Cc: <stable@vger.kernel.org> # v4.11+
Signed-off-by: Takashi Iwai <tiwai@suse.de>

This reverts commit 89b593c3 ("ALSA: usb-audio: purge needless
variable length array").  The patch turned out to cause a severe
regression, triggering an Oops at snd_usb_ctl_msg().  It was overseen
that snd_usb_ctl_msg() writes back the response to the given buffer,
while the patch changed it to a read-only const buffer.  (One should
always double-check when an extra pointer cast is present...)

As a simple fix, just revert the affected commit.  It was merely a
cleanup.  Although it brings VLA again, it's clearer as a fix.  We'll
address the VLA later in another patch.

Fixes: 89b593c3 ("ALSA: usb-audio: purge needless variable length array")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=195875
Cc: <stable@vger.kernel.org> # v4.11+
Signed-off-by: Takashi Iwai <tiwai@suse.de>

This effectively reverts commit 8ee74a91 ("proc: try to remove use
of FOLL_FORCE entirely")

It turns out that people do depend on FOLL_FORCE for the /proc/<pid>/mem
case, and we're talking not just debuggers. Talking to the affected people, the use-cases are:

Keno Fischer:
 "We used these semantics as a hardening mechanism in the julia JIT. By
  opening /proc/self/mem and using these semantics, we could avoid
  needing RWX pages, or a dual mapping approach. We do have fallbacks to
  these other methods (though getting EIO here actually causes an assert
  in released versions - we'll updated that to make sure to take the
  fall back in that case).

  Nevertheless the /proc/self/mem approach was our favored approach
  because it a) Required an attacker to be able to execute syscalls
  which is a taller order than getting memory write and b) didn't double
  the virtual address space requirements (as a dual mapping approach
  would).

  I think in general this feature is very useful for anybody who needs
  to precisely control the execution of some other process. Various
  debuggers (gdb/lldb/rr) certainly fall into that category, but there's
  another class of such processes (wine, various emulators) which may
  want to do that kind of thing.

  Now, I suspect most of these will have the other process under ptrace
  control, so maybe allowing (same_mm || ptraced) would be ok, but at
  least for the sandbox/remote-jit use case, it would be perfectly
  reasonable to not have the jit server be a ptracer"

Robert O'Callahan:
 "We write to readonly code and data mappings via /proc/.../mem in lots
  of different situations, particularly when we're adjusting program
  state during replay to match the recorded execution.

  Like Julia, we can add workarounds, but they could be expensive."

so not only do people use FOLL_FORCE for both reads and writes, but they
use it for both the local mm and remote mm.

With these comments in mind, we likely also cannot add the "are we
actively ptracing" check either, so this keeps the new code organization
and does not do a real revert that would add back the original comment
about "Maybe we should limit FOLL_FORCE to actual ptrace users?"
Reported-by: Keno Fischer <keno@juliacomputing.com>
Reported-by: Robert O'Callahan <robert@ocallahan.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>