2023-07-05 06:14:22

by Rahul Rameshbabu

Subject: [PATCH HID v1] HID: nvidia-shield: Pack inner/related declarations in HOSTCMD reports

Match alignment information in composite type declarations used by packed
HOSTCMD report structures. Compiler packing attribute is not recursive for
inner declarations. Mismatched alignment information can cause undefined
behavior in code generated for accessing composite type members. struct
pointers passed to thunderstrike_parse_board_info_payload and
thunderstrike_parse_haptics_payload are an example of this being
potentially problematic since alignment information from the packed HOSTCMD
report is lost.

Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Link: https://github.com/llvm/llvm-project/issues/55520#issuecomment-1128617570
Link: https://gcc.gnu.org/onlinedocs/gcc-13.1.0/gcc/Common-Type-Attributes.html#index-packed-type-attribute
Signed-off-by: Rahul Rameshbabu <[email protected]>
---
drivers/hid/hid-nvidia-shield.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hid/hid-nvidia-shield.c b/drivers/hid/hid-nvidia-shield.c
index 85700cec5eac..a928ad2be62d 100644
--- a/drivers/hid/hid-nvidia-shield.c
+++ b/drivers/hid/hid-nvidia-shield.c
@@ -63,12 +63,12 @@ static_assert(sizeof(enum thunderstrike_led_state) == 1);
struct thunderstrike_hostcmd_board_info {
__le16 revision;
__le16 serial[7];
-};
+} __packed;

struct thunderstrike_hostcmd_haptics {
u8 motor_left;
u8 motor_right;
-};
+} __packed;

struct thunderstrike_hostcmd_resp_report {
u8 report_id; /* THUNDERSTRIKE_HOSTCMD_RESP_REPORT_ID */
@@ -81,7 +81,7 @@ struct thunderstrike_hostcmd_resp_report {
__le16 fw_version;
enum thunderstrike_led_state led_state;
u8 payload[30];
- };
+ } __packed;
} __packed;
static_assert(sizeof(struct thunderstrike_hostcmd_resp_report) ==
THUNDERSTRIKE_HOSTCMD_REPORT_SIZE);
@@ -92,15 +92,15 @@ struct thunderstrike_hostcmd_req_report {
u8 reserved_at_10;

union {
- struct {
+ struct __packed {
u8 update;
enum thunderstrike_led_state state;
} led;
- struct {
+ struct __packed {
u8 update;
struct thunderstrike_hostcmd_haptics motors;
} haptics;
- };
+ } __packed;
u8 reserved_at_30[27];
} __packed;
static_assert(sizeof(struct thunderstrike_hostcmd_req_report) ==
--
2.40.1

2023-07-10 09:06:30

by Benjamin Tissoires

Subject: Re: [PATCH HID v1] HID: nvidia-shield: Pack inner/related declarations in HOSTCMD reports

On Tue, 04 Jul 2023 23:04:14 -0700, Rahul Rameshbabu wrote:
> Match alignment information in composite type declarations used by packed
> HOSTCMD report structures. Compiler packing attribute is not recursive for
> inner declarations. Mismatched alignment information can cause undefined
> behavior in code generated for accessing composite type members. struct
> pointers passed to thunderstrike_parse_board_info_payload and
> thunderstrike_parse_haptics_payload are an example of this being
> potentially problematic since alignment information from the packed HOSTCMD
> report is lost.
>
> [...]

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git (for-6.5/upstream-fixes), thanks!

[1/1] HID: nvidia-shield: Pack inner/related declarations in HOSTCMD reports
https://git.kernel.org/hid/hid/c/8bcf314b92ed

Cheers,
--
Benjamin Tissoires <[email protected]>