Commit 8cb6aafc authored by Julien Thierry's avatar Julien Thierry Committed by Stefan Bader

ARM: 8794/1: uaccess: Prevent speculative use of the current addr_limit

BugLink: https://bugs.launchpad.net/bugs/1852110

Commit 621afc67 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.

Porting commit c2f0ad4f ("arm64: uaccess: Prevent speculative use
of the current addr_limit").
Signed-off-by: default avatarJulien Thierry <julien.thierry@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarDavid A. Long <dave.long@linaro.org>
Reviewed-by: default avatarJulien Thierry <julien.thierry@arm.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarConnor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: default avatarKhalid Elmously <khalid.elmously@canonical.com>
parent 0385505c
...@@ -99,6 +99,14 @@ extern int __put_user_bad(void); ...@@ -99,6 +99,14 @@ extern int __put_user_bad(void);
static inline void set_fs(mm_segment_t fs) static inline void set_fs(mm_segment_t fs)
{ {
current_thread_info()->addr_limit = fs; current_thread_info()->addr_limit = fs;
/*
* Prevent a mispredicted conditional call to set_fs from forwarding
* the wrong address limit to access_ok under speculation.
*/
dsb(nsh);
isb();
modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER); modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);
} }
......
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