From: Michael Ellerman mpe@ellerman.id.au
commit 51973a815c6b46d7b23b68d6af371ad1c9d503ca upstream.
Our syscall entry is done in assembly so patch in an explicit barrier_nospec.
Based on a patch by Michal Suchanek.
Signed-off-by: Michal Suchanek msuchanek@suse.de Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/kernel/entry_64.S | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -36,6 +36,7 @@ #include <asm/hw_irq.h> #include <asm/context_tracking.h> #include <asm/tm.h> +#include <asm/barrier.h> #ifdef CONFIG_PPC_BOOK3S #include <asm/exception-64s.h> #else @@ -177,6 +178,15 @@ system_call: /* label this so stack tr clrldi r8,r8,32 15: slwi r0,r0,4 + + barrier_nospec_asm + /* + * Prevent the load of the handler below (based on the user-passed + * system call number) being speculatively executed until the test + * against NR_syscalls and branch to .Lsyscall_enosys above has + * committed. + */ + ldx r12,r11,r0 /* Fetch system call handler [ptr] */ mtctr r12 bctrl /* Call handler */