linux-stable.git/include/linux, branch v5.3.11

kvm: Add helper function for creating VM worker threads

2019-11-12T18:28:30+00:00

commit c57c80467f90e5504c8df9ad3555d2c78800bf94 upstream.

Add a function to create a kernel thread associated with a given VM. In
particular, it ensures that the worker thread inherits the priority and
cgroups of the calling thread.

Signed-off-by: Junaid Shahid 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

kvm: x86, powerpc: do not allow clearing largepages debugfs entry

2019-11-12T18:28:29+00:00

commit 833b45de69a6016c4b0cebe6765d526a31a81580 upstream.

The largepages debugfs entry is incremented/decremented as shadow
pages are created or destroyed.  Clearing it will result in an
underflow, which is harmless to KVM but ugly (and could be
misinterpreted by tools that use debugfs information), so make
this particular statistic read-only.

Signed-off-by: Paolo Bonzini 
Signed-off-by: Thomas Gleixner 
Cc: kvm-ppc@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

cpu/speculation: Uninline and export CPU mitigations helpers

2019-11-12T18:28:29+00:00

commit 731dc9df975a5da21237a18c3384f811a7a41cc6 upstream.

A kernel module may need to check the value of the "mitigations=" kernel
command line parameter as part of its setup when the module needs
to perform software mitigations for a CPU flaw.

Uninline and export the helper functions surrounding the cpu_mitigations
enum to allow for their usage from a module.

Lastly, privatize the enum and cpu_mitigations variable since the value of
cpu_mitigations can be checked with the exported helper functions.

Signed-off-by: Tyler Hicks 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

x86/bugs: Add ITLB_MULTIHIT bug infrastructure

2019-11-12T18:28:28+00:00

commit db4d30fbb71b47e4ecb11c4efa5d8aad4b03dfae upstream.

Some processors may incur a machine check error possibly resulting in an
unrecoverable CPU lockup when an instruction fetch encounters a TLB
multi-hit in the instruction TLB. This can occur when the page size is
changed along with either the physical address or cache type. The relevant
erratum can be found here:

   https://bugzilla.kernel.org/show_bug.cgi?id=205195

There are other processors affected for which the erratum does not fully
disclose the impact.

This issue affects both bare-metal x86 page tables and EPT.

It can be mitigated by either eliminating the use of large pages or by
using careful TLB invalidations when changing the page size in the page
tables.

Just like Spectre, Meltdown, L1TF and MDS, a new bit has been allocated in
MSR_IA32_ARCH_CAPABILITIES (PSCHANGE_MC_NO) and will be set on CPUs which
are mitigated against this issue.

Signed-off-by: Vineela Tummalapalli 
Co-developed-by: Pawan Gupta 
Signed-off-by: Pawan Gupta 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

x86/speculation/taa: Add sysfs reporting for TSX Async Abort

2019-11-12T18:28:27+00:00

commit 6608b45ac5ecb56f9e171252229c39580cc85f0f upstream.

Add the sysfs reporting file for TSX Async Abort. It exposes the
vulnerability and the mitigation state similar to the existing files for
the other hardware vulnerabilities.

Sysfs file path is:
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort

Signed-off-by: Pawan Gupta 
Signed-off-by: Borislav Petkov 
Signed-off-by: Thomas Gleixner 
Tested-by: Neelima Krishnan 
Reviewed-by: Mark Gross 
Reviewed-by: Tony Luck 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Josh Poimboeuf 
Signed-off-by: Greg Kroah-Hartman

x86, efi: Never relocate kernel below lowest acceptable address

2019-11-12T18:28:15+00:00

[ Upstream commit 220dd7699c46d5940115bd797b01b2ab047c87b8 ]

Currently, kernel fails to boot on some HyperV VMs when using EFI.
And it's a potential issue on all x86 platforms.

It's caused by broken kernel relocation on EFI systems, when below three
conditions are met:

1. Kernel image is not loaded to the default address (LOAD_PHYSICAL_ADDR)
   by the loader.
2. There isn't enough room to contain the kernel, starting from the
   default load address (eg. something else occupied part the region).
3. In the memmap provided by EFI firmware, there is a memory region
   starts below LOAD_PHYSICAL_ADDR, and suitable for containing the
   kernel.

EFI stub will perform a kernel relocation when condition 1 is met. But
due to condition 2, EFI stub can't relocate kernel to the preferred
address, so it fallback to ask EFI firmware to alloc lowest usable memory
region, got the low region mentioned in condition 3, and relocated
kernel there.

It's incorrect to relocate the kernel below LOAD_PHYSICAL_ADDR. This
is the lowest acceptable kernel relocation address.

The first thing goes wrong is in arch/x86/boot/compressed/head_64.S.
Kernel decompression will force use LOAD_PHYSICAL_ADDR as the output
address if kernel is located below it. Then the relocation before
decompression, which move kernel to the end of the decompression buffer,
will overwrite other memory region, as there is no enough memory there.

To fix it, just don't let EFI stub relocate the kernel to any address
lower than lowest acceptable address.

[ ardb: introduce efi_low_alloc_above() to reduce the scope of the change ]

Signed-off-by: Kairui Song 
Signed-off-by: Ard Biesheuvel 
Acked-by: Jarkko Sakkinen 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191029173755.27149-6-ardb@kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

SUNRPC: Destroy the back channel when we destroy the host transport

2019-11-12T18:28:14+00:00

[ Upstream commit 669996add4c92476e0f8d6b4cd2bb308d1939fd7 ]

When we're destroying the host transport mechanism, we should ensure
that we do not leak memory by failing to release any back channel
slots that might still exist.

Reported-by: Neil Brown 
Reported-by: kbuild test robot 
Signed-off-by: Trond Myklebust 
Signed-off-by: Anna Schumaker 
Signed-off-by: Sasha Levin

bpf: Fix use after free in subprog's jited symbol removal

2019-11-12T18:27:44+00:00

[ Upstream commit cd7455f1013ef96d5cbf5c05d2b7c06f273810a6 ]

syzkaller managed to trigger the following crash:

  [...]
  BUG: unable to handle page fault for address: ffffc90001923030
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD aa551067 P4D aa551067 PUD aa552067 PMD a572b067 PTE 80000000a1173163
  Oops: 0000 [#1] PREEMPT SMP KASAN
  CPU: 0 PID: 7982 Comm: syz-executor912 Not tainted 5.4.0-rc3+ #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:bpf_jit_binary_hdr include/linux/filter.h:787 [inline]
  RIP: 0010:bpf_get_prog_addr_region kernel/bpf/core.c:531 [inline]
  RIP: 0010:bpf_tree_comp kernel/bpf/core.c:600 [inline]
  RIP: 0010:__lt_find include/linux/rbtree_latch.h:115 [inline]
  RIP: 0010:latch_tree_find include/linux/rbtree_latch.h:208 [inline]
  RIP: 0010:bpf_prog_kallsyms_find kernel/bpf/core.c:674 [inline]
  RIP: 0010:is_bpf_text_address+0x184/0x3b0 kernel/bpf/core.c:709
  [...]
  Call Trace:
   kernel_text_address kernel/extable.c:147 [inline]
   __kernel_text_address+0x9a/0x110 kernel/extable.c:102
   unwind_get_return_address+0x4c/0x90 arch/x86/kernel/unwind_frame.c:19
   arch_stack_walk+0x98/0xe0 arch/x86/kernel/stacktrace.c:26
   stack_trace_save+0xb6/0x150 kernel/stacktrace.c:123
   save_stack mm/kasan/common.c:69 [inline]
   set_track mm/kasan/common.c:77 [inline]
   __kasan_kmalloc+0x11c/0x1b0 mm/kasan/common.c:510
   kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:518
   slab_post_alloc_hook mm/slab.h:584 [inline]
   slab_alloc mm/slab.c:3319 [inline]
   kmem_cache_alloc+0x1f5/0x2e0 mm/slab.c:3483
   getname_flags+0xba/0x640 fs/namei.c:138
   getname+0x19/0x20 fs/namei.c:209
   do_sys_open+0x261/0x560 fs/open.c:1091
   __do_sys_open fs/open.c:1115 [inline]
   __se_sys_open fs/open.c:1110 [inline]
   __x64_sys_open+0x87/0x90 fs/open.c:1110
   do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  [...]

After further debugging it turns out that we walk kallsyms while in parallel
we tear down a BPF program which contains subprograms that have been JITed
though the program itself has not been fully exposed and is eventually bailing
out with error.

The bpf_prog_kallsyms_del_subprogs() in bpf_prog_load()'s error path removes
the symbols, however, bpf_prog_free() tears down the JIT memory too early via
scheduled work. Instead, it needs to properly respect RCU grace period as the
kallsyms walk for BPF is under RCU.

Fix it by refactoring __bpf_prog_put()'s tear down and reuse it in our error
path where we defer final destruction when we have subprogs in the program.

Fixes: 7d1982b4e335 ("bpf: fix panic in prog load calls cleanup")
Fixes: 1c2a088a6626 ("bpf: x64: add JIT support for multi-function programs")
Reported-by: syzbot+710043c5d1d5b5013bc7@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov 
Tested-by: syzbot+710043c5d1d5b5013bc7@syzkaller.appspotmail.com
Link: https://lore.kernel.org/bpf/55f6367324c2d7e9583fa9ccf5385dcbba0d7a6e.1571752452.git.daniel@iogearbox.net
Signed-off-by: Sasha Levin

mm: thp: handle page cache THP correctly in PageTransCompoundMap

2019-11-12T18:26:56+00:00

commit 169226f7e0d275c1879551f37484ef6683579a5c upstream.

We have a usecase to use tmpfs as QEMU memory backend and we would like
to take the advantage of THP as well.  But, our test shows the EPT is
not PMD mapped even though the underlying THP are PMD mapped on host.
The number showed by /sys/kernel/debug/kvm/largepage is much less than
the number of PMD mapped shmem pages as the below:

  7f2778200000-7f2878200000 rw-s 00000000 00:14 262232 /dev/shm/qemu_back_mem.mem.Hz2hSf (deleted)
  Size:            4194304 kB
  [snip]
  AnonHugePages:         0 kB
  ShmemPmdMapped:   579584 kB
  [snip]
  Locked:                0 kB

  cat /sys/kernel/debug/kvm/largepages
  12

And some benchmarks do worse than with anonymous THPs.

By digging into the code we figured out that commit 127393fbe597 ("mm:
thp: kvm: fix memory corruption in KVM with THP enabled") checks if
there is a single PTE mapping on the page for anonymous THP when setting
up EPT map.  But the _mapcount < 0 check doesn't work for page cache THP
since every subpage of page cache THP would get _mapcount inc'ed once it
is PMD mapped, so PageTransCompoundMap() always returns false for page
cache THP.  This would prevent KVM from setting up PMD mapped EPT entry.

So we need handle page cache THP correctly.  However, when page cache
THP's PMD gets split, kernel just remove the map instead of setting up
PTE map like what anonymous THP does.  Before KVM calls get_user_pages()
the subpages may get PTE mapped even though it is still a THP since the
page cache THP may be mapped by other processes at the mean time.

Checking its _mapcount and whether the THP has PTE mapped or not.
Although this may report some false negative cases (PTE mapped by other
processes), it looks not trivial to make this accurate.

With this fix /sys/kernel/debug/kvm/largepage would show reasonable
pages are PMD mapped by EPT as the below:

  7fbeaee00000-7fbfaee00000 rw-s 00000000 00:14 275464 /dev/shm/qemu_back_mem.mem.SKUvat (deleted)
  Size:            4194304 kB
  [snip]
  AnonHugePages:         0 kB
  ShmemPmdMapped:   557056 kB
  [snip]
  Locked:                0 kB

  cat /sys/kernel/debug/kvm/largepages
  271

And the benchmarks are as same as anonymous THPs.

[yang.shi@linux.alibaba.com: v4]
  Link: http://lkml.kernel.org/r/1571865575-42913-1-git-send-email-yang.shi@linux.alibaba.com
Link: http://lkml.kernel.org/r/1571769577-89735-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: dd78fedde4b9 ("rmap: support file thp")
Signed-off-by: Yang Shi 
Reported-by: Gang Deng 
Tested-by: Gang Deng 
Suggested-by: Hugh Dickins 
Acked-by: Kirill A. Shutemov 
Cc: Andrea Arcangeli 
Cc: Matthew Wilcox 
Cc: 	[4.8+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

net/tls: fix sk_msg trim on fallback to copy mode

2019-11-12T18:26:39+00:00

[ Upstream commit 683916f6a84023407761d843048f1aea486b2612 ]

sk_msg_trim() tries to only update curr pointer if it falls into
the trimmed region. The logic, however, does not take into the
account pointer wrapping that sk_msg_iter_var_prev() does nor
(as John points out) the fact that msg->sg is a ring buffer.

This means that when the message was trimmed completely, the new
curr pointer would have the value of MAX_MSG_FRAGS - 1, which is
neither smaller than any other value, nor would it actually be
correct.

Special case the trimming to 0 length a little bit and rework
the comparison between curr and end to take into account wrapping.

This bug caused the TLS code to not copy all of the message, if
zero copy filled in fewer sg entries than memcopy would need.

Big thanks to Alexander Potapenko for the non-KMSAN reproducer.

v2:
 - take into account that msg->sg is a ring buffer (John).

Link: https://lore.kernel.org/netdev/20191030160542.30295-1-jakub.kicinski@netronome.com/ (v1)

Fixes: d829e9c4112b ("tls: convert to generic sk_msg interface")
Reported-by: syzbot+f8495bff23a879a6d0bd@syzkaller.appspotmail.com
Reported-by: syzbot+6f50c99e8f6194bf363f@syzkaller.appspotmail.com
Co-developed-by: John Fastabend 
Signed-off-by: Jakub Kicinski 
Signed-off-by: John Fastabend 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman