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
c2f0ad4fc089cff8 ("arm64: uaccess: Prevent speculative use
of the current addr_limit").
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
static inline void set_fs(mm_segment_t 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);
}