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Mitchell Levy 55c834bc9f x86/fpu: Avoid writing LBR bit to IA32_XSS unless supported 
commit 2848ff28d1 upstream.

There are two distinct CPU features related to the use of XSAVES and LBR:
whether LBR is itself supported and whether XSAVES supports LBR. The LBR
subsystem correctly checks both in intel_pmu_arch_lbr_init(), but the
XSTATE subsystem does not.

The LBR bit is only removed from xfeatures_mask_independent when LBR is not
supported by the CPU, but there is no validation of XSTATE support.

If XSAVES does not support LBR the write to IA32_XSS causes a #GP fault,
leaving the state of IA32_XSS unchanged, i.e. zero. The fault is handled
with a warning and the boot continues.

Consequently the next XRSTORS which tries to restore supervisor state fails
with #GP because the RFBM has zero for all supervisor features, which does
not match the XCOMP_BV field.

As XFEATURE_MASK_FPSTATE includes supervisor features setting up the FPU
causes a #GP, which ends up in fpu_reset_from_exception_fixup(). That fails
due to the same problem resulting in recursive #GPs until the kernel runs
out of stack space and double faults.

Prevent this by storing the supported independent features in
fpu_kernel_cfg during XSTATE initialization and use that cached value for
retrieving the independent feature bits to be written into IA32_XSS.

[ tglx: Massaged change log ]

Fixes: f0dccc9da4 ("x86/fpu/xstate: Support dynamic supervisor feature for LBR")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240812-xsave-lbr-fix-v3-1-95bac1bf62f4@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-09-12 11:11:28 +02:00
arch x86/fpu: Avoid writing LBR bit to IA32_XSS unless supported 2024-09-12 11:11:28 +02:00
block block: remove the blk_flush_integrity call in blk_integrity_unregister 2024-09-08 07:54:47 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: aead,cipher - zeroize key buffer after use 2024-07-11 12:49:04 +02:00
Documentation hwspinlock: Introduce hwspin_lock_bust() 2024-09-08 07:54:43 +02:00
drivers net: mctp-serial: Fix missing escapes on transmit 2024-09-12 11:11:28 +02:00
fs eventfs: Use list_del_rcu() for SRCU protected list variable 2024-09-12 11:11:27 +02:00
include net: mana: Fix error handling in mana_create_txq/rxq's NAPI cleanup 2024-09-12 11:11:27 +02:00
init rust: fix the default format for CONFIG_{RUSTC,BINDGEN}_VERSION_TEXT 2024-08-29 17:33:29 +02:00
io_uring io_uring: fix io_match_task must_hold 2024-08-03 08:54:41 +02:00
ipc sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table) 2024-08-11 12:47:13 +02:00
kernel tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread() 2024-09-12 11:11:27 +02:00
lib sched/topology: Handle NUMA_NO_NODE in sched_numa_find_nth_cpu() 2024-08-29 17:33:24 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm userfaultfd: fix checks for huge PMDs 2024-09-12 11:11:27 +02:00
net Bluetooth: MGMT: Ignore keys being loaded with invalid type 2024-09-12 11:11:26 +02:00
rust rust: macros: provide correct provenance when constructing THIS_MODULE 2024-09-12 11:11:25 +02:00
samples bpf: Replace bpf_lpm_trie_key 0-length array with flexible array 2024-08-19 06:04:27 +02:00
scripts rust: work around bindgen 0.69.0 issue 2024-08-29 17:33:29 +02:00
security smack: tcp: ipv4, fix incorrect labeling 2024-09-08 07:54:45 +02:00
sound ALSA: hda/realtek: Support mute LED on HP Laptop 14-dq2xxx 2024-09-12 11:11:24 +02:00
tools selftests: mptcp: join: stop transfer when check is done (part 2.2) 2024-09-08 07:54:35 +02:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.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: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
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 pwm: Rename pwm_apply_state() to pwm_apply_might_sleep() 2024-06-12 11:12:24 +02:00
Makefile Linux 6.6.50 2024-09-08 07:54:49 +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.