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2913b778 GKH |
1 | From 9478f1927e6ef9ef5e1ad761af1c98aa8e40b7f5 Mon Sep 17 00:00:00 2001 |
2 | From: Mark Rutland <mark.rutland@arm.com> | |
3 | Date: Tue, 3 Apr 2018 11:22:51 +0100 | |
4 | Subject: arm64: only advance singlestep for user instruction traps | |
5 | ||
6 | From: Mark Rutland <mark.rutland@arm.com> | |
7 | ||
8 | commit 9478f1927e6ef9ef5e1ad761af1c98aa8e40b7f5 upstream. | |
9 | ||
10 | Our arm64_skip_faulting_instruction() helper advances the userspace | |
11 | singlestep state machine, but this is also called by the kernel BRK | |
12 | handler, as used for WARN*(). | |
13 | ||
14 | Thus, if we happen to hit a WARN*() while the user singlestep state | |
15 | machine is in the active-no-pending state, we'll advance to the | |
16 | active-pending state without having executed a user instruction, and | |
17 | will take a step exception earlier than expected when we return to | |
18 | userspace. | |
19 | ||
20 | Let's fix this by only advancing the state machine when skipping a user | |
21 | instruction. | |
22 | ||
23 | Signed-off-by: Mark Rutland <mark.rutland@arm.com> | |
24 | Cc: Andrey Konovalov <andreyknvl@google.com> | |
25 | Cc: Catalin Marinas <catalin.marinas@arm.com> | |
26 | Cc: Will Deacon <will.deacon@arm.com> | |
27 | Signed-off-by: Will Deacon <will.deacon@arm.com> | |
28 | Signed-off-by: Andrey Konovalov <andreyknvl@google.com> | |
29 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
30 | ||
31 | --- | |
32 | arch/arm64/kernel/traps.c | 3 ++- | |
33 | 1 file changed, 2 insertions(+), 1 deletion(-) | |
34 | ||
35 | --- a/arch/arm64/kernel/traps.c | |
36 | +++ b/arch/arm64/kernel/traps.c | |
37 | @@ -304,7 +304,8 @@ void arm64_skip_faulting_instruction(str | |
38 | * If we were single stepping, we want to get the step exception after | |
39 | * we return from the trap. | |
40 | */ | |
41 | - user_fastforward_single_step(current); | |
42 | + if (user_mode(regs)) | |
43 | + user_fastforward_single_step(current); | |
44 | } | |
45 | ||
46 | static LIST_HEAD(undef_hook); |