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Filename Latest commit message Latest commit date
Pawan Gupta b58882c69f x86/speculation: Add LFENCE to RSB fill sequence
commit ba6e31af2be96c4d0536f2152ed6f7b6c11bca47 upstream.

RSB fill sequence does not have any protection for miss-prediction of
conditional branch at the end of the sequence. CPU can speculatively
execute code immediately after the sequence, while RSB filling hasn't
completed yet.

  #define __FILL_RETURN_BUFFER(reg, nr, sp)	\
  	mov	$(nr/2), reg;			\
  771:						\
  	call	772f;				\
  773:	/* speculation trap */			\
  	pause;					\
  	lfence;					\
  	jmp	773b;				\
  772:						\
  	call	774f;				\
  775:	/* speculation trap */			\
  	pause;					\
  	lfence;					\
  	jmp	775b;				\
  774:						\
  	dec	reg;				\
  	jnz	771b;  <----- CPU can miss-predict here.				\
  	add	$(BITS_PER_LONG/8) * nr, sp;

Before RSB is filled, RETs that come in program order after this macro
can be executed speculatively, making them vulnerable to RSB-based
attacks.

Mitigate it by adding an LFENCE after the conditional branch to prevent
speculation while RSB is being filled.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-08-11 12:57:53 +02:00
arch x86/speculation: Add LFENCE to RSB fill sequence 2022-08-11 12:57:53 +02:00
block
certs
crypto
Documentation x86/speculation: Add RSB VM Exit protections 2022-08-11 12:57:53 +02:00
drivers macintosh/adb: fix oob read in do_adb_query() function 2022-08-11 12:57:53 +02:00
fs ntfs: fix use-after-free in ntfs_ucsncmp() 2022-08-03 11:59:37 +02:00
include ipv6/addrconf: fix a null-ptr-deref bug for ip6_ptr 2022-08-03 11:59:39 +02:00
init
ipc
kernel bpf: Verifer, adjust_scalar_min_max_vals to always call update_reg_bounds() 2022-08-11 12:57:51 +02:00
lib locking/refcount: Consolidate implementations of refcount_t 2022-07-29 17:14:17 +02:00
LICENSES
mm mm/mempolicy: fix uninit-value in mpol_rebind_policy() 2022-07-29 17:14:16 +02:00
net sctp: leave the err path free in sctp_stream_init to sctp_stream_free 2022-08-03 11:59:41 +02:00
samples
scripts modpost: fix section mismatch check for exported init/exit sections 2022-06-29 08:58:49 +02:00
security ima: remove the IMA_TEMPLATE Kconfig option 2022-07-29 17:14:16 +02:00
sound ALSA: memalloc: Align buffer allocations in page size 2022-07-29 17:14:18 +02:00
tools x86/speculation: Add RSB VM Exit protections 2022-08-11 12:57:53 +02:00
usr
virt KVM: Don't null dereference ops->destroy 2022-08-11 12:57:52 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.209 2022-08-03 11:59:42 +02:00
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.