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Aruna Ramakrishna dd9478d54c x86/pkeys: Ensure updated PKRU value is XRSTOR'd 
[ Upstream commit ae6012d72f ]

When XSTATE_BV[i] is 0, and XRSTOR attempts to restore state component
'i' it ignores any value in the XSAVE buffer and instead restores the
state component's init value.

This means that if XSAVE writes XSTATE_BV[PKRU]=0 then XRSTOR will
ignore the value that update_pkru_in_sigframe() writes to the XSAVE buffer.

XSTATE_BV[PKRU] only gets written as 0 if PKRU is in its init state. On
Intel CPUs, basically never happens because the kernel usually
overwrites the init value (aside: this is why we didn't notice this bug
until now). But on AMD, the init tracker is more aggressive and will
track PKRU as being in its init state upon any wrpkru(0x0).
Unfortunately, sig_prepare_pkru() does just that: wrpkru(0x0).

This writes XSTATE_BV[PKRU]=0 which makes XRSTOR ignore the PKRU value
in the sigframe.

To fix this, always overwrite the sigframe XSTATE_BV with a value that
has XSTATE_BV[PKRU]==1.  This ensures that XRSTOR will not ignore what
update_pkru_in_sigframe() wrote.

The problematic sequence of events is something like this:

Userspace does:
	* wrpkru(0xffff0000) (or whatever)
	* Hardware sets: XINUSE[PKRU]=1
Signal happens, kernel is entered:
	* sig_prepare_pkru() => wrpkru(0x00000000)
	* Hardware sets: XINUSE[PKRU]=0 (aggressive AMD init tracker)
	* XSAVE writes most of XSAVE buffer, including
	  XSTATE_BV[PKRU]=XINUSE[PKRU]=0
	* update_pkru_in_sigframe() overwrites PKRU in XSAVE buffer
... signal handling
	* XRSTOR sees XSTATE_BV[PKRU]==0, ignores just-written value
	  from update_pkru_in_sigframe()

Fixes: 70044df250 ("x86/pkeys: Update PKRU to enable all pkeys before XSAVE")
Suggested-by: Rudi Horn <rudi.horn@oracle.com>
Signed-off-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/all/20241119174520.3987538-3-aruna.ramakrishna%40oracle.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-12-14 20:03:16 +01:00
arch x86/pkeys: Ensure updated PKRU value is XRSTOR'd 2024-12-14 20:03:16 +01:00
block block: don't verify IO lock for freeze/unfreeze in elevator_init_mq() 2024-12-05 14:03:10 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: pcrypt - Call crypto layer directly when padata_do_parallel() return -EBUSY 2024-12-05 14:01:18 +01:00
Documentation dt-bindings: net: fec: add pps channel property 2024-12-09 10:41:11 +01:00
drivers nvme: don't apply NVME_QUIRK_DEALLOCATE_ZEROES when DSM is not supported 2024-12-14 20:03:16 +01:00
fs f2fs: fix to requery extent which cross boundary of inquiry 2024-12-14 20:03:12 +01:00
include i3c: master: Extend address status bit to 4 and add I3C_ADDR_SLOT_EXT_DESIRED 2024-12-14 20:03:12 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring: check for overflows in io_pin_pages 2024-12-05 14:02:50 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel ntp: Remove invalid cast in time offset math 2024-12-14 20:03:12 +01:00
lib maple_tree: refine mas_store_root() on storing NULL 2024-12-09 10:41:01 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/vmalloc: combine all TLB flush operations of KASAN shadow virtual address into one operation 2024-12-09 10:41:08 +01:00
net tcp_bpf: Fix the sk_mem_uncharge logic in tcp_bpf_sendmsg 2024-12-14 20:03:14 +01:00
rust rust: block: fix formatting of kernel::block::mq::request module 2024-12-05 14:02:21 +01:00
samples kfifo: don't include dma-mapping.h in kfifo.h 2024-12-05 14:03:03 +01:00
scripts modpost: remove incorrect code in do_eisa_entry() 2024-12-05 14:03:08 +01:00
security apparmor: test: Fix memory leak for aa_unpack_strdup() 2024-12-05 14:02:46 +01:00
sound ASoC: SOF: ipc3-topology: fix resource leaks in sof_ipc3_widget_setup_comp_dai() 2024-12-14 20:03:15 +01:00
tools tools: Override makefile ARCH variable if defined, but empty 2024-12-14 20:03:15 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -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 self from DSA entry 2024-11-03 12:52:38 -08:00
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 MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile Linux 6.12.4 2024-12-09 10:41:16 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.