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Sebastian Andrzej Siewior 0b455673e7 x86/fpu: Deactivate FPU state after failure during state load
[ Upstream commit bbc55341b9c67645d1a5471506370caf7dd4a203 ]

In __fpu__restore_sig(), fpu_fpregs_owner_ctx needs to be reset if the
FPU state was not fully restored. Otherwise the following may happen (on
the same CPU):

  Task A                     Task B               fpu_fpregs_owner_ctx
  *active*                                        A.fpu
  __fpu__restore_sig()
                             ctx switch           load B.fpu
                             *active*             B.fpu
  fpregs_lock()
  copy_user_to_fpregs_zeroing()
    copy_kernel_to_xregs() *modify*
    copy_user_to_xregs() *fails*
  fpregs_unlock()
                            ctx switch            skip loading B.fpu,
                            *active*              B.fpu

In the success case, fpu_fpregs_owner_ctx is set to the current task.

In the failure case, the FPU state might have been modified by loading
the init state.

In this case, fpu_fpregs_owner_ctx needs to be reset in order to ensure
that the FPU state of the following task is loaded from saved state (and
not skipped because it was the previous state).

Reset fpu_fpregs_owner_ctx after a failure during restore occurred, to
ensure that the FPU state for the next task is always loaded.

The problem was debugged-by Yu-cheng Yu <yu-cheng.yu@intel.com>.

 [ bp: Massage commit message. ]

Fixes: 5f409e20b7 ("x86/fpu: Defer FPU state load until return to userspace")
Reported-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191220195906.plk6kpmsrikvbcfn@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-02-24 08:36:26 +01:00
arch x86/fpu: Deactivate FPU state after failure during state load 2020-02-24 08:36:26 +01:00
block block: fix memleak of bio integrity data 2020-01-26 10:01:09 +01:00
certs
crypto crypto: testmgr - don't try to decrypt uninitialized buffers 2020-02-14 16:34:18 -05:00
Documentation dt-bindings: iio: adc: ad7606: Fix wrong maxItems value 2020-02-14 16:34:19 -05:00
drivers iommu/vt-d: Fix off-by-one in PASID allocation 2020-02-24 08:36:26 +01:00
fs ext4: fix ext4_dax_read/write inode locking sequence for IOCB_NOWAIT 2020-02-24 08:36:24 +01:00
include rcu: Fix data-race due to atomic_t copy-by-value 2020-02-24 08:36:23 +01:00
init Revert "um: Enable CONFIG_CONSTRUCTORS" 2020-02-01 09:34:53 +00:00
ipc ipc/msg.c: consolidate all xxxctl_down() functions 2020-02-11 04:35:07 -08:00
kernel printk: fix exclusive_console replaying 2020-02-24 08:36:24 +01:00
lib lib/test_kasan.c: fix memory leak in kmalloc_oob_krealloc_more() 2020-02-11 04:35:14 -08:00
LICENSES
mm mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush 2020-02-11 04:35:42 -08:00
net net/sched: flower: add missing validation of TCA_FLOWER_FLAGS 2020-02-24 08:36:22 +01:00
samples samples/bpf: Xdp_redirect_cpu fix missing tracepoint attach 2020-02-11 04:35:29 -08:00
scripts scripts/find-unused-docs: Fix massive false positives 2020-02-11 04:35:23 -08:00
security selinux: fall back to ref-walk if audit is required 2020-02-14 16:34:20 -05:00
sound ALSA: ctl: allow TLV read operation for callback type of element in locked case 2020-02-24 08:36:24 +01:00
tools perf stat: Don't report a null stalled cycles per insn metric 2020-02-19 19:53:08 +01:00
usr gen_initramfs_list.sh: fix 'bad variable name' error 2020-01-09 10:20:00 +01:00
virt KVM: arm64: Treat emulated TVAL TimerValue as a signed 32-bit integer 2020-02-14 16:34:18 -05:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: correct entries for ISDN/mISDN section 2020-02-11 04:35:06 -08:00
Makefile Linux 5.4.21 2020-02-19 19:53:10 +01:00
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.