linux

iv/linux

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Brian Geffon 64e0b5894c x86/fpu: Correct pkru/xstate inconsistency

When eagerly switching PKRU in switch_fpu_finish() it checks that
current is not a kernel thread as kernel threads will never use PKRU.
It's possible that this_cpu_read_stable() on current_task
(ie. get_current()) is returning an old cached value. To resolve this
reference next_p directly rather than relying on current.

As written it's possible when switching from a kernel thread to a
userspace thread to observe a cached PF_KTHREAD flag and never restore
the PKRU. And as a result this issue only occurs when switching
from a kernel thread to a userspace thread, switching from a non kernel
thread works perfectly fine because all that is considered in that
situation are the flags from some other non kernel task and the next fpu
is passed in to switch_fpu_finish().

This behavior only exists between 5.2 and 5.13 when it was fixed by a
rewrite decoupling PKRU from xstate, in:
  commit 954436989cc5 ("x86/fpu: Remove PKRU handling from switch_fpu_finish()")

Unfortunately backporting the fix from 5.13 is probably not realistic as
it's part of a 60+ patch series which rewrites most of the PKRU handling.

Fixes: 0cecca9d03c9 ("x86/fpu: Eager switch PKRU state")
Signed-off-by: Brian Geffon <bgeffon@google.com>
Signed-off-by: Willis Kung <williskung@google.com>
Tested-by: Willis Kung <williskung@google.com>
Cc: <stable@vger.kernel.org> # v5.4.x
Cc: <stable@vger.kernel.org> # v5.10.x
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2022-03-02 11:41:03 +01:00

alpha

alpha: Declare virt_to_phys and virt_to_bus parameter as pointer to volatile

2021-09-30 10:09:26 +02:00

arc

ARC: export clear_user_page() for modules

2021-09-22 12:26:45 +02:00

arm

ARM: OMAP2+: adjust the location of put_device() call in omapdss_init_of

2022-02-23 12:00:00 +01:00

arm64

arm64: dts: meson-g12: drop BL32 region from SEI510/SEI610