tree f9f010bc975fc6f0a577d5f0921b1d3642b2ab5c
parent faac72dc91507049c55f3de6731428f50f33fc88
author Russell King <rmk+kernel@armlinux.org.uk> 1539617534 -0400
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1539846988 +0200

ARM: vfp: use __copy_from_user() when restoring VFP state

Commit 42019fc50dfadb219f9e6ddf4c354f3837057d80 upstream.

__get_user_error() is used as a fast accessor to make copying structure
members in the signal handling path as efficient as possible.  However,
with software PAN and the recent Spectre variant 1, the efficiency is
reduced as these are no longer fast accessors.

In the case of software PAN, it has to switch the domain register around
each access, and with Spectre variant 1, it would have to repeat the
access_ok() check for each access.

Use __copy_from_user() rather than __get_user_err() for individual
members when restoring VFP state.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David A. Long <dave.long@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>