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Breno Leitao 92c77807d9 KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 
commit 49f683b41f upstream.

Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the
loads and stores are atomic.  In the extremely unlikely scenario the
compiler tears the stores, it's theoretically possible for KVM to attempt
to get a vCPU using an out-of-bounds index, e.g. if the write is split
into multiple 8-bit stores, and is paired with a 32-bit load on a VM with
257 vCPUs:

  CPU0                              CPU1
  last_boosted_vcpu = 0xff;

                                    (last_boosted_vcpu = 0x100)
                                    last_boosted_vcpu[15:8] = 0x01;
  i = (last_boosted_vcpu = 0x1ff)
                                    last_boosted_vcpu[7:0] = 0x00;

  vcpu = kvm->vcpu_array[0x1ff];

As detected by KCSAN:

  BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm]

  write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16:
  kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm
  handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel
  vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:?
		 arch/x86/kvm/vmx/vmx.c:6606) kvm_intel
  vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm
  kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm
  kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm
  __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890)
  __x64_sys_ioctl (fs/ioctl.c:890)
  x64_sys_call (arch/x86/entry/syscall_64.c:33)
  do_syscall_64 (arch/x86/entry/common.c:?)
  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

  read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4:
  kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm
  handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel
  vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:?
			arch/x86/kvm/vmx/vmx.c:6606) kvm_intel
  vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm
  kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm
  kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm
  __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890)
  __x64_sys_ioctl (fs/ioctl.c:890)
  x64_sys_call (arch/x86/entry/syscall_64.c:33)
  do_syscall_64 (arch/x86/entry/common.c:?)
  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

  value changed: 0x00000012 -> 0x00000000

Fixes: 217ece6129 ("KVM: use yield_to instead of sleep in kvm_vcpu_on_spin")
Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20240510092353.2261824-1-leitao@debian.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-06-27 13:46:21 +02:00
arch MIPS: dts: bcm63268: Add missing properties to the TWD node 2024-06-27 13:46:21 +02:00
block block/ioctl: prefer different overflow check 2024-06-27 13:46:15 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: ecrdsa - Fix module auto-load on add_key 2024-06-16 13:41:37 +02:00
Documentation mm: fix race between __split_huge_pmd_locked() and GUP-fast 2024-06-16 13:41:38 +02:00
drivers net: usb: ax88179_178a: improve reset check 2024-06-27 13:46:21 +02:00
fs cifs: fix typo in module parameter enable_gcm_256 2024-06-27 13:46:21 +02:00
include tty: add the option to have a tty reject a new ldisc 2024-06-27 13:46:17 +02:00
init smp: Provide 'setup_max_cpus' definition on UP too 2024-06-16 13:41:42 +02:00
io_uring io_uring/sqpoll: work around a potential audit memory leak 2024-06-27 13:46:14 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel tracing: Build event generation tests only as modules 2024-06-27 13:46:18 +02:00
lib maple_tree: fix mas_empty_area_rev() null pointer dereference 2024-06-16 13:41:31 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/memory-failure: fix handling of dissolved but not taken off from buddy pages 2024-06-21 14:35:59 +02:00
net net: do not leave a dangling sk pointer, when socket creation fails 2024-06-27 13:46:21 +02:00
rust rust: macros: fix soundness issue in module! macro 2024-05-17 11:56:17 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:12:28 +01:00
scripts scripts/gdb: fix SB_* constants parsing 2024-06-16 13:41:32 +02:00
security landlock: Fix d_parent walk 2024-06-21 14:35:43 +02:00
sound ALSA: hda/realtek: Enable headset mic on IdeaPad 330-17IKB 81DM 2024-06-27 13:46:18 +02:00
tools kselftest: arm64: Add a null pointer check 2024-06-27 13:46:15 +02:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:46:21 +02:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add leah to 6.1 MAINTAINERS file 2024-05-17 11:56:16 +02:00
Makefile kbuild: Remove support for Clang's ThinLTO caching 2024-06-27 13:46:21 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.