From: Mark Rutland <mark.rutl...@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.rutl...@arm.com>
Cc: Andrey Konovalov <andreyk...@google.com>
Cc: Catalin Marinas <catalin.mari...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Andrey Konovalov <andreyk...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@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);
