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Pawan Gupta 07dbb10f15 x86/bhi: Add support for clearing branch history at syscall entry
commit 7390db8aea upstream.

Branch History Injection (BHI) attacks may allow a malicious application to
influence indirect branch prediction in kernel by poisoning the branch
history. eIBRS isolates indirect branch targets in ring0.  The BHB can
still influence the choice of indirect branch predictor entry, and although
branch predictor entries are isolated between modes when eIBRS is enabled,
the BHB itself is not isolated between modes.

Alder Lake and new processors supports a hardware control BHI_DIS_S to
mitigate BHI.  For older processors Intel has released a software sequence
to clear the branch history on parts that don't support BHI_DIS_S. Add
support to execute the software sequence at syscall entry and VMexit to
overwrite the branch history.

For now, branch history is not cleared at interrupt entry, as malicious
applications are not believed to have sufficient control over the
registers, since previous register state is cleared at interrupt
entry. Researchers continue to poke at this area and it may become
necessary to clear at interrupt entry as well in the future.

This mitigation is only defined here. It is enabled later.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Co-developed-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-04-10 16:28:35 +02:00
arch x86/bhi: Add support for clearing branch history at syscall entry 2024-04-10 16:28:35 +02:00
block block: Do not force full zone append completion in req_bio_endio() 2024-04-03 15:19:49 +02:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: jitter - fix CRYPTO_JITTERENTROPY help text 2024-03-26 18:20:50 -04:00
Documentation x86/cpu: Enable STIBP on AMD if Automatic IBRS is enabled 2024-04-03 15:19:54 +02:00
drivers nvme: fix miss command type check 2024-04-10 16:28:35 +02:00
fs smb: client: fix potential UAF in cifs_signal_cifsd_for_reconnect() 2024-04-10 16:28:34 +02:00
include mm/secretmem: fix GUP-fast succeeding on secretmem folios 2024-04-10 16:28:34 +02:00
init init: open /initrd.image with O_LARGEFILE 2024-04-03 15:19:47 +02:00
io_uring io_uring/net: correctly handle multishot recvmsg retry setup 2024-04-03 15:19:33 +02:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: Protect against int overflow for stack access size 2024-04-10 16:28:23 +02:00
lib pci_iounmap(): Fix MMIO mapping leak 2024-04-03 15:19:25 +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 x86/mm/pat: fix VM_PAT handling in COW mappings 2024-04-10 16:28:33 +02:00
net mptcp: don't account accept() of non-MPC client as fallback to TCP 2024-04-10 16:28:34 +02:00
rust rust: allocator: Prevent mis-aligned allocation 2023-08-11 12:08:18 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:12:28 +01:00
scripts scripts/bpf_doc: Use silent mode when exec make cmd 2024-04-10 16:28:21 +02:00
security landlock: Warn once if a Landlock action is requested while disabled 2024-04-03 15:19:32 +02:00
sound ALSA: hda/realtek: Update Panasonic CF-SZ6 quirk to support headset with microphone 2024-04-10 16:28:32 +02:00
tools selftests: mptcp: display simult in extra_msg 2024-04-10 16:28:34 +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: Always flush async #PF workqueue when vCPU is being destroyed 2024-04-03 15:19:25 +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 trace: Relocate event helper files 2024-03-06 14:45:17 +00:00
Makefile Linux 6.1.84 2024-04-03 15:19:55 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.