Fix the crash like this:

BUG: Kernel NULL pointer dereference on read at 0x00000000
Faulting instruction address: 0xc000000000c3447c
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
CPU: 11 PID: 7519 Comm: lt-ndctl Not tainted 5.6.0-rc7-autotest #1
...
NIP [c000000000c3447c] vmemmap_populated+0x98/0xc0
LR [c000000000088354] vmemmap_free+0x144/0x320
Call Trace:
section_deactivate+0x220/0x240
__remove_pages+0x118/0x170
arch_remove_memory+0x3c/0x150
memunmap_pages+0x1cc/0x2f0
devm_action_release+0x30/0x50
release_nodes+0x2f8/0x3e0
device_release_driver_internal+0x168/0x270
unbind_store+0x130/0x170
drv_attr_store+0x44/0x60
sysfs_kf_write+0x68/0x80
kernfs_fop_write+0x100/0x290
__vfs_write+0x3c/0x70
vfs_write+0xcc/0x240
ksys_write+0x7c/0x140
system_call+0x5c/0x68

The crash is due to NULL dereference at

test_bit(idx, ms->usage->subsection_map);

due to ms->usage = NULL in pfn_section_valid()

With commit d41e2f3bd546 ("mm/hotplug: fix hot remove failure in
SPARSEMEM|!VMEMMAP case") section_mem_map is set to NULL after
depopulate_section_mem(). This was done so that pfn_page() can work
correctly with kernel config that disables SPARSEMEM_VMEMMAP. With that
config pfn_to_page does

__section_mem_map_addr(__sec) + __pfn;

where

static inline struct page *__section_mem_map_addr(struct mem_section *section)
{
unsigned long map = section->section_mem_map;
map &= SECTION_MAP_MASK;
return (struct page *)map;
}

Now with SPASEMEM_VMEMAP enabled, mem_section->usage->subsection_map is
used to check the pfn validity (pfn_valid()). Since section_deactivate
release mem_section->usage if a section is fully deactivated,
pfn_valid() check after a subsection_deactivate cause a kernel crash.

static inline int pfn_valid(unsigned long pfn)
{
...
return early_section(ms) || pfn_section_valid(ms, pfn);
}

where

static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
{
int idx = subsection_map_index(pfn);

return test_bit(idx, ms->usage->subsection_map);
}

Avoid this by clearing SECTION_HAS_MEM_MAP when mem_section->usage is
freed. For architectures like ppc64 where large pages are used for
vmmemap mapping (16MB), a specific vmemmap mapping can cover multiple
sections. Hence before a vmemmap mapping page can be freed, the kernel
needs to make sure there are no valid sections within that mapping.
Clearing the section valid bit before depopulate_section_memap enables
this.

[aneesh.kumar@linux.ibm.com: add comment]
Link: http://lkml.kernel.org/r/20200326133235.343616-1-aneesh.kumar@linux.ibm.comLink: http://lkml.kernel.org/r/20200325031914.107660-1-aneesh.kumar@linux.ibm.com
Fixes: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Depending on CONFIG_VMAP_STACK and the THREAD_SIZE / PAGE_SIZE ratio the
space for task stacks can be allocated using __vmalloc_node_range(),
alloc_pages_node() and kmem_cache_alloc_node().

In the first and the second cases page->mem_cgroup pointer is set, but
in the third it's not: memcg membership of a slab page should be
determined using the memcg_from_slab_page() function, which looks at
page->slab_cache->memcg_params.memcg . In this case, using
mod_memcg_page_state() (as in account_kernel_stack()) is incorrect:
page->mem_cgroup pointer is NULL even for pages charged to a non-root
memory cgroup.

It can lead to kernel_stack per-memcg counters permanently showing 0 on
some architectures (depending on the configuration).

In order to fix it, let's introduce a mod_memcg_obj_state() helper,
which takes a pointer to a kernel object as a first argument, uses
mem_cgroup_from_obj() to get a RCU-protected memcg pointer and calls
mod_memcg_state(). It allows to handle all possible configurations
(CONFIG_VMAP_STACK and various THREAD_SIZE/PAGE_SIZE values) without
spilling any memcg/kmem specifics into fork.c .

Note: This is a special version of the patch created for stable
backports. It contains code from the following two patches:
- mm: memcg/slab: introduce mem_cgroup_from_obj()
- mm: fork: fix kernel_stack memcg stats for various stack implementations

[guro@fb.com: introduce mem_cgroup_from_obj()]
Link: http://lkml.kernel.org/r/20200324004221.GA36662@carbon.dhcp.thefacebook.com
Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages")
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200303233550.251375-1-guro@fb.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This appears to be a mistake in commit faced7e0806cf ("mm: hugetlb
controller for cgroups v2").

Essentially that commit does a hugetlb_cgroup_from_counter assuming that
page_counter_try_charge has initialized counter.

But if that has failed then it seems will not initialize counter, so
hugetlb_cgroup_from_counter(counter) ends up pointing to random memory,
causing kasan to complain.

The solution is to simply use 'h_cg', instead of
hugetlb_cgroup_from_counter(counter), since that is a reference to the
hugetlb_cgroup anyway. After this change kasan ceases to complain.

Fixes: faced7e0806cf ("mm: hugetlb controller for cgroups v2")
Reported-by: syzbot+cac0c4e204952cf449b1@syzkaller.appspotmail.com
Signed-off-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Giuseppe Scrivano <gscrivan@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/20200313223920.124230-1-almasrymina@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We see multiple issues with the implementation/interface to compute
whether a memory block can be offlined (exposed via
/sys/devices/system/memory/memoryX/removable) and would like to simplify
it (remove the implementation).

1. It runs basically lockless. While this might be good for performance,
we see possible races with memory offlining that will require at
least some sort of locking to fix.

2. Nowadays, more false positives are possible. No arch-specific checks
are performed that validate if memory offlining will not be denied
right away (and such check will require locking). For example, arm64
won't allow to offline any memory block that was added during boot -
which will imply a very high error rate. Other archs have other
constraints.

3. The interface is inherently racy. E.g., if a memory block is detected
to be removable (and was not a false positive at that time), there is
still no guarantee that offlining will actually succeed. So any
caller already has to deal with false positives.

4. It is unclear which performance benefit this interface actually
provides. The introducing commit 5c755e9fd813 ("memory-hotplug: add
sysfs removable attribute for hotplug memory remove") mentioned

"A user-level agent must be able to identify which sections
of memory are likely to be removable before attempting the
potentially expensive operation."

However, no actual performance comparison was included.

Known users:

- lsmem: Will group memory blocks based on the "removable" property. [1]

- chmem: Indirect user. It has a RANGE mode where one can specify
removable ranges identified via lsmem to be offlined. However,
it also has a "SIZE" mode, which allows a sysadmin to skip the
manual "identify removable blocks" step. [2]

- powerpc-utils: Uses the "removable" attribute to skip some memory
blocks right away when trying to find some to offline+remove.
However, with ballooning enabled, it already skips this
information completely (because it once resulted in many false
negatives). Therefore, the implementation can deal with false
positives properly already. [3]

According to Nathan Fontenot, DLPAR on powerpc is nowadays no longer
driven from userspace via the drmgr command (powerpc-utils). Nowadays
it's managed in the kernel - including onlining/offlining of memory
blocks - triggered by drmgr writing to /sys/kernel/dlpar. So the
affected legacy userspace handling is only active on old kernels. Only
very old versions of drmgr on a new kernel (unlikely) might execute
slower - totally acceptable.

With CONFIG_MEMORY_HOTREMOVE, always indicating "removable" should not
break any user space tool. We implement a very bad heuristic now.
Without CONFIG_MEMORY_HOTREMOVE we cannot offline anything, so report
"not removable" as before.

Original discussion can be found in [4] ("[PATCH RFC v1] mm:
is_mem_section_removable() overhaul").

Other users of is_mem_section_removable() will be removed next, so that
we can remove is_mem_section_removable() completely.

[1] http://man7.org/linux/man-pages/man1/lsmem.1.html
[2] http://man7.org/linux/man-pages/man8/chmem.8.html
[3] https://github.com/ibm-power-utilities/powerpc-utils
[4] https://lkml.kernel.org/r/20200117105759.27905-1-david@redhat.com

Also, this patch probably fixes a crash reported by Steve.
http://lkml.kernel.org/r/CAPcyv4jpdaNvJ67SkjyUJLBnBnXXQv686BiVW042g03FUmWLXw@mail.gmail.com

Reported-by: "Scargall, Steve" <steve.scargall@intel.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Nathan Fontenot <ndfont@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Robert Jennings <rcj@linux.vnet.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Karel Zak <kzak@redhat.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200128093542.6908-1-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

claim_swapfile() currently keeps the inode locked when it is successful,
or the file is already swapfile (with -EBUSY). And, on the other error
cases, it does not lock the inode.

This inconsistency of the lock state and return value is quite confusing
and actually causing a bad unlock balance as below in the "bad_swap"
section of __do_sys_swapon().

This commit fixes this issue by moving the inode_lock() and IS_SWAPFILE
check out of claim_swapfile(). The inode is unlocked in
"bad_swap_unlock_inode" section, so that the inode is ensured to be
unlocked at "bad_swap". Thus, error handling codes after the locking now
jumps to "bad_swap_unlock_inode" instead of "bad_swap".

=====================================
WARNING: bad unlock balance detected!
5.5.0-rc7+ #176 Not tainted
-------------------------------------
swapon/4294 is trying to release lock (&sb->s_type->i_mutex_key) at: __do_sys_swapon+0x94b/0x3550
but there are no more locks to release!

other info that might help us debug this:
no locks held by swapon/4294.

stack backtrace:
CPU: 5 PID: 4294 Comm: swapon Not tainted 5.5.0-rc7-BTRFS-ZNS+ #176
Hardware name: ASUS All Series/H87-PRO, BIOS 2102 07/29/2014
Call Trace:
dump_stack+0xa1/0xea
print_unlock_imbalance_bug.cold+0x114/0x123
lock_release+0x562/0xed0
up_write+0x2d/0x490
__do_sys_swapon+0x94b/0x3550
__x64_sys_swapon+0x54/0x80
do_syscall_64+0xa4/0x4b0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f15da0a0dc7

Fixes: 1638045c3677 ("mm: set S_SWAPFILE on blockdev swap devices")
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Qais Youef <qais.yousef@arm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200206090132.154869-1-naohiro.aota@wdc.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull SCSI fixes from James Bottomley:
"Two small fixes: one in drivers (qla2xxx), and one in the core (sd) to
try to cope with USB enclosures that silently change reported
parameters"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: sd: Fix optimal I/O size for devices that change reported values
scsi: qla2xxx: Fix I/Os being passed down when FC device is being deleted

Pull parsic fix from Helge Deller:
"Fix a recursive loop when running 'make ARCH=parisc defconfig'"

* 'parisc-5.6-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Fix defconfig selection

Some USB bridge devices will return a default set of characteristics during
initialization. And then, once an attached drive has spun up, substitute
the actual parameters reported by the drive. According to the SCSI spec,
the device should return a UNIT ATTENTION in case any reported parameters
change. But in this case the change is made silently after a small window
where default values are reported.

Commit a83da8a4509d ("scsi: sd: Optimal I/O size should be a multiple of
physical block size") validated the reported optimal I/O size against the
physical block size to overcome problems with devices reporting nonsensical
transfer sizes. However, this validation did not account for the fact that
aforementioned devices will return default values during a brief window
during spin-up. The subsequent change in reported characteristics would
invalidate the checking that had previously been performed.

Unset a previously configured optimal I/O size should the sanity checking
fail on subsequent revalidate attempts.

Link: https://lore.kernel.org/r/33fb522e-4f61-1b76-914f-c9e6a3553c9b@gmail.com
Cc: Bryan Gurney <bgurney@redhat.com>
Cc: <stable@vger.kernel.org>
Reported-by: Bernhard Sulzer <micraft.b@gmail.com>
Tested-by: Bernhard Sulzer <micraft.b@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Pull ARM DT and driver fixes from Arnd Bergmann:
"For the devicetree files, there are a total of 20 patches, almost
entirely for 32-bit machines:

- The Allwinner/sun9i r40 SoC dtsi file contains a number of issues,
both for correctness and for style that are addressed in separate
patches. This causes most of the changed lines of the DT updates
this time.

- More Allwinner updates fixing the identification of the security
system on sun8i/A33, a recent regression of the A83t ethernet, and
a few board specific issues on the TBS-A711 macine.

- Several bug fixes for OMAP dts files, most notably fixing the
timings for the NAND flash on the Nokia N900 that regressed a while
ago after the move to configuring them from DT. Some other OMAPs
now set the correct dma limits on the L3 bus, and a regression fix
addresses lost Ethernet on dm814x

- One incorrect setting in the newly added Raspberry Pi Zero W that
may cause issues with the SD card controller.

- A missing property on the bcm2835 firmware node caused incorrect
DMA settings.

- An old bug on the oxnas platform causing spurious interrupts is
finally addressed.

- A regression on the Exynos Midas board broke the OLED panel power
supply.

- The i.MX6 phycore SoM specified the wrong voltage for the SoC, this
is now set to the values from the datasheet.

- Some 64-bit machines use a deprecated string to identify the PSCI
firmware.

There are also several small code fixes addressing mostly serious
issues:

- Fix the sunxi rsb bus access to no longer return incorrect data
when mixing 8 and 16 bit I/O.

- Fix a suspend/resume regression on the OMAP2+ lcdc from a missing
quirk in the ti-sysc driver

- Fix a NULL pointer access from a race in the fsl dpio driver

- Fix a v5.5 regression in the exynos-chipid driver that caused an
invalid error code probing the device on non-exynos platforms

- Fix an out-of-bounds access in the AMD TEE driver"

* tag 'arm-soc-fixes-5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (24 commits)
soc: samsung: chipid: Fix return value on non-Exynos platforms
arm64: dts: Fix leftover entry-methods for PSCI
ARM: dts: exynos: Fix regulator node aliasing on Midas-based boards
ARM: dts: oxnas: Fix clear-mask property
ARM: dts: bcm283x: Fix vc4's firmware bus DMA limitations
ARM: dts: omap5: Add bus_dma_limit for L3 bus
ARM: dts: omap4-droid4: Fix lost touchscreen interrupts
ARM: dts: dra7: Add bus_dma_limit for L3 bus
ARM: bcm2835-rpi-zero-w: Add missing pinctrl name
ARM: dts: sun8i: a33: add the new SS compatible
dt-bindings: crypto: add new compatible for A33 SS
ARM: dts: sun8i: r40: Move SPI device nodes based on address order
ARM: dts: sun8i: r40: Fix register base address for SPI2 and SPI3
ARM: dts: sun8i: r40: Move AHCI device node based on address order
ARM: dts: imx6: phycore-som: fix arm and soc minimum voltage
soc: fsl: dpio: register dpio irq handlers after dpio create
tee: amdtee: out of bounds read in find_session()
ARM: dts: N900: fix onenand timings
bus: ti-sysc: Fix quirk flags for lcdc on am335x
ARM: dts: Fix dm814x Ethernet by changing to use rgmii-id mode
...

Fix the recursive loop when running "make ARCH=parisc defconfig".

Fixes: 84669923e1ed ("parisc: Regenerate parisc defconfigs")
Noticed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Helge Deller <deller@gmx.de>

I/Os could be passed down while the device FC SCSI device is being deleted.
This would result in unnecessary delay of I/O and driver messages (when
extended logging is set).

[mkp: fixed commit hash and added SoB for Nilesh]

Link: https://lore.kernel.org/r/20200313085001.3781-1-njavali@marvell.com
Fixes: 3c75ad1d87c7 ("scsi: qla2xxx: Remove defer flag to indicate immeadiate port loss") # v5.6-rc1+
Tested-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Arun Easi <aeasi@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Pull RISC-V fixes from Palmer Dabbelt:
"Sorry for the last minute patches, but a few things fell through the
cracks recently. I was on the fence about sending a late pull request
just for the M-mode fixes, as we don't really have any users, but the
last patch fixes the build for Fedora which I consider pretty
important.

Given that the M-mode fixes should be very low risk, I figured it's
worth sending them along as well.

Thhis passes my standard 'boot in QEMU' test"

* tag 'riscv-for-linus-5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
RISC-V: Move all address space definition macros to one place
RISC-V: Only select essential drivers for SOC_VIRT config
riscv: fix the IPI missing issue in nommu mode
riscv: uaccess should be used in nommu mode

Correct the probe return value to -ENODEV on non-Exynos platforms.

Link: https://lore.kernel.org/r/20200316175652.5604-4-krzk@kernel.org
Fixes: 02fb29882d5c ("soc: samsung: chipid: Drop "syscon" compatible requirement")
Cc: <stable@vger.kernel.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>