From: Mark Rutland mark.rutland@arm.com
commit 9478f1927e6ef9ef5e1ad761af1c98aa8e40b7f5 upstream.
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@arm.com Cc: Andrey Konovalov andreyknvl@google.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Andrey Konovalov andreyknvl@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -304,7 +304,8 @@ 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);