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Sean Christopherson 52d5afedf3 KVM: VMX: Mark RCX, RDX and RSI as clobbered in vmx_vcpu_run()'s asm blob Based on upstream commit `f3689e3f17`. Save RCX, RDX and RSI to fake outputs to coerce the compiler into treating them as clobbered. RCX in particular is likely to be reused by the compiler to dereference the 'struct vcpu_vmx' pointer, which will result in a null pointer dereference now that RCX is zeroed by the asm blob. Tag the asm() blob as volatile to prevent GCC from dropping the blob, which is possible now that the blob has output values, all of which are unused. Upstream commit `f3689e3f17` ("KVM: VMX: Save RSI to an unused output in the vCPU-run asm blob") is not a direct equivalent of this patch. As its shortlog states, it only tagged RSI as clobbered, whereas here RCX and RDX are also clobbered. In upstream at the time of the offending commit (`b4be98039a` in 4.19, `0e0ab73c9a` upstream), the inline asm blob had previously been moved to a dedicated helper, __vmx_vcpu_run(). For unrelated reasons, __vmx_vcpu_run() was put into its own optimization unit, which for all intents and purposes made it impossible to consume clobbered registers because RCX, RDX and RSI are volatile and __vmx_vcpu_run() couldn't itself be inlined. In other words, the bug existed but couldn't be hit. Similarly, the lack of "volatile" was also a bug in upstream that was hidden by an unrelated change that exists in upstream but not in 4.19. In this case, the asm blob also uses ASM_CALL_CONSTRAINT (marks RSP as being an input/output constraint) in upstream to play nice with objtool due the blob making a CALL. In 4.19, there is no CALL and thus no ASM_CALL_CONSTRAINT. Furthermore, both of the lurking bugs were blasted away in upstream by commits `5e0781df18` ("KVM: VMX: Move vCPU-run code to a proper assembly routine") and `fc2ba5a27a` ("KVM: VMX: Call vCPU-run asm sub-routine from C and remove clobbering"), i.e. these bugs will never be directly fixed in upstream. Reported-by: Tobias Urdin <tobias.urdin@binero.com> Fixes: `b4be98039a` ("KVM: VMX: Zero out all general purpose registers after VM-Exit") Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-05-14 07:57:21 +02:00
arch	KVM: VMX: Mark RCX, RDX and RSI as clobbered in vmx_vcpu_run()'s asm blob	2020-05-14 07:57:21 +02:00
block	block, bfq: fix use-after-free in bfq_idle_slice_timer_body	2020-04-17 10:48:42 +02:00
certs	export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()	2018-08-22 23:21:44 +09:00
crypto	crypto: api - Fix race condition in crypto_spawn_alg	2020-02-11 04:34:05 -08:00
Documentation	arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419	2020-04-29 16:31:08 +02:00
drivers	staging: gasket: Check the return value of gasket_get_bar_index()	2020-05-14 07:57:21 +02:00
firmware	Fix built-in early-load Intel microcode alignment	2020-01-23 08:21:29 +01:00
fs	coredump: fix crash when umh is disabled	2020-05-14 07:57:21 +02:00
include	net: stricter validation of untrusted gso packets	2020-05-14 07:57:19 +02:00
init	fork: fix some -Wmissing-prototypes warnings	2019-12-05 09:21:04 +01:00
ipc	ipc/util.c: sysvipc_find_ipc() should increase position index	2020-04-29 16:31:13 +02:00
kernel	coredump: fix crash when umh is disabled	2020-05-14 07:57:21 +02:00
lib	lib: devres: add a helper function for ioremap_uc	2020-05-10 10:30:11 +02:00
LICENSES	LICENSES: Remove CC-BY-SA-4.0 license text	2018-10-18 11:28:50 +02:00
mm	mm/page_alloc: fix watchdog soft lockups during set_zone_contiguous()	2020-05-14 07:57:21 +02:00
net	sctp: Fix bundling of SHUTDOWN with COOKIE-ACK	2020-05-14 07:57:20 +02:00
samples	vmalloc: fix remap_vmalloc_range() bounds checks	2020-04-29 16:31:27 +02:00
scripts	scripts/config: allow colons in option strings for sed	2020-05-10 10:30:09 +02:00
security	selinux: properly handle multiple messages in selinux_netlink_send()	2020-05-06 08:13:32 +02:00
sound	ALSA: hda: Match both PCI ID and SSID for driver blacklist	2020-05-10 10:30:12 +02:00
tools	selftests/ipc: Fix test failure seen after initial test run	2020-05-10 10:30:06 +02:00
usr	initramfs: restore default compression behavior	2020-04-13 10:44:59 +02:00
virt	KVM: arm64: Fix 32bit PC wrap-around	2020-05-14 07:57:20 +02:00
.clang-format	clang-format: Set IndentWrappedFunctionNames false	2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	Kbuild updates for v4.17 (2nd)	2018-04-15 17:21:30 -07:00
.mailmap	libnvdimm-for-4.19_misc	2018-08-25 18:13:10 -07:00
COPYING	COPYING: use the new text with points to the license files	2018-03-23 12:41:45 -06:00
CREDITS	9p: remove Ron Minnich from MAINTAINERS	2018-08-17 16:20:26 -07:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt	2018-08-02 08:06:55 +09:00
MAINTAINERS	MAINTAINERS: Update drm/i915 bug filing URL	2020-02-28 16:38:49 +01:00
Makefile	Linux 4.19.122	2020-05-10 10:30:13 +02:00
README	Docs: Added a pointer to the formatted docs to README	2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.