redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity
Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
879,022 Commits
15 Branches
0 Tags
3.4 GiB
C 97.7%
Assembly 1.4%
Makefile 0.3%
Shell 0.2%
Python 0.1%
Other 0.1%
 
 
 
 
 
 
Go to file
Anthony Steinhauser 9d1dcba6dd x86/speculation: Prevent rogue cross-process SSBD shutdown 
commit dbbe2ad02e upstream.

On context switch the change of TIF_SSBD and TIF_SPEC_IB are evaluated
to adjust the mitigations accordingly. This is optimized to avoid the
expensive MSR write if not needed.

This optimization is buggy and allows an attacker to shutdown the SSBD
protection of a victim process.

The update logic reads the cached base value for the speculation control
MSR which has neither the SSBD nor the STIBP bit set. It then OR's the
SSBD bit only when TIF_SSBD is different and requests the MSR update.

That means if TIF_SSBD of the previous and next task are the same, then
the base value is not updated, even if TIF_SSBD is set. The MSR write is
not requested.

Subsequently if the TIF_STIBP bit differs then the STIBP bit is updated
in the base value and the MSR is written with a wrong SSBD value.

This was introduced when the per task/process conditional STIPB
switching was added on top of the existing SSBD switching.

It is exploitable if the attacker creates a process which enforces SSBD
and has the contrary value of STIBP than the victim process (i.e. if the
victim process enforces STIBP, the attacker process must not enforce it;
if the victim process does not enforce STIBP, the attacker process must
enforce it) and schedule it on the same core as the victim process. If
the victim runs after the attacker the victim becomes vulnerable to
Spectre V4.

To fix this, update the MSR value independent of the TIF_SSBD difference
and dependent on the SSBD mitigation method available. This ensures that
a subsequent STIPB initiated MSR write has the correct state of SSBD.

[ tglx: Handle X86_FEATURE_VIRT_SSBD & X86_FEATURE_VIRT_SSBD correctly
        and massaged changelog ]

Fixes: 5bfbe3ad58 ("x86/speculation: Prepare for per task indirect branch speculation control")
Signed-off-by: Anthony Steinhauser <asteinhauser@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-06-17 16:40:25 +02:00
Documentation x86/speculation: Add Ivy Bridge to affected list 2020-06-10 20:24:58 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch x86/speculation: Prevent rogue cross-process SSBD shutdown 2020-06-17 16:40:25 +02:00
block Revert "block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT" 2020-06-03 08:21:27 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto gcc-10: avoid shadowing standard library 'free()' in crypto 2020-05-20 08:20:29 +02:00
drivers iwlwifi: mvm: fix NVM check for 3168 devices 2020-06-17 16:40:24 +02:00
fs aio: fix async fsync creds 2020-06-17 16:40:24 +02:00
include mm: add kvfree_sensitive() for freeing sensitive data objects 2020-06-17 16:40:23 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel padata: add separate cpuhp node for CPUHP_PADATA_DEAD 2020-06-17 16:40:22 +02:00
lib vsprintf: don't obfuscate NULL and error pointers 2020-05-27 17:46:43 +02:00
mm mm: add kvfree_sensitive() for freeing sensitive data objects 2020-06-17 16:40:23 +02:00
net sctp: fix refcount bug in sctp_wfree 2020-06-17 16:40:24 +02:00
samples samples: bpf: Fix build error 2020-06-03 08:21:15 +02:00
scripts bpf: Support llvm-objcopy for vmlinux BTF 2020-06-17 16:40:20 +02:00
security mm: add kvfree_sensitive() for freeing sensitive data objects 2020-06-17 16:40:23 +02:00
sound ASoC: intel - fix the card names 2020-06-07 13:18:49 +02:00
tools selftests: fix flower parent qdisc 2020-06-17 16:40:23 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm: vgic: Synchronize the whole guest on GIC{D,R}_I{S,C}ACTIVER read 2020-05-20 08:20:04 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 17:22:19 +01:00
Makefile Linux 5.4.46 2020-06-10 20:24:58 +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.