4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mark Rutland <mark.rutland@xxxxxxx> [ Upstream commit 9478f1927e6ef9ef5e1ad761af1c98aa8e40b7f5 ] Our arm64_skip_faulting_instruction() helper advances the userspace singlestep state machine, but this is also called by the kernel BRK handler, as used for WARN*(). Thus, if we happen to hit a WARN*() while the user singlestep state machine is in the active-no-pending state, we'll advance to the active-pending state without having executed a user instruction, and will take a step exception earlier than expected when we return to userspace. Let's fix this by only advancing the state machine when skipping a user instruction. Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/traps.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -243,7 +243,8 @@ void arm64_skip_faulting_instruction(str * If we were single stepping, we want to get the step exception after * we return from the trap. */ - user_fastforward_single_step(current); + if (user_mode(regs)) + user_fastforward_single_step(current); } static LIST_HEAD(undef_hook);
