arm64: uaccess: Prevent speculative use of the current addr_limit
authorMark Rutland <mark.rutland@arm.com>
Thu, 12 Apr 2018 11:11:03 +0000 (12:11 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 20 Apr 2018 06:20:43 +0000 (08:20 +0200)
commit346edd61ce1ce5f2a2a3e81518d86b2b239ed4d4
treeee4b0c5784b5f97d69b8a2fad1a478d1408f9216
parentf3ed64a6273ebdc1ddf22262c4e5f724688b7393
arm64: uaccess: Prevent speculative use of the current addr_limit

From: Will Deacon <will.deacon@arm.com>

commit c2f0ad4fc089cff81cef6a13d04b399980ecbfcc upstream.

A mispredicted conditional call to set_fs could result in the wrong
addr_limit being forwarded under speculation to a subsequent access_ok
check, potentially forming part of a spectre-v1 attack using uaccess
routines.

This patch prevents this forwarding from taking place, but putting heavy
barriers in set_fs after writing the addr_limit.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]
Tested-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/arm64/include/asm/uaccess.h