Hi all,
On 26/07/24 14:07, Linus Walleij wrote:
Hi Haoyu,
On Wed, Jul 24, 2024 at 11:12 AM Haoyu Li <[email protected]> wrote:
Dear Linux Developers for GPIO SUBSYSTEM,
We are curious about the use of `struct ljca_gpio_packet *packet` in the
function `ljca_gpio_config`
(https://elixir.bootlin.com/linux/v6.10/source/drivers/gpio/gpio-ljca.c#L80).
```
static int ljca_gpio_config(struct ljca_gpio_dev *ljca_gpio, u8 gpio_id,
u8 config)
{
struct ljca_gpio_packet *packet =
(struct ljca_gpio_packet *)ljca_gpio->obuf;
int ret;
mutex_lock(&ljca_gpio->trans_lock);
packet->item[0].index = gpio_id;
packet->item[0].value = config | ljca_gpio->connect_mode[gpio_id];
packet->num = 1;
ret = ljca_transfer(ljca_gpio->ljca, LJCA_GPIO_CONFIG, (u8 *)packet,
struct_size(packet, item, packet->num), NULL, 0);
mutex_unlock(&ljca_gpio->trans_lock);
return ret < 0 ? ret : 0;
}
```
The definition of `struct ljca_gpio_packet` is at
https://elixir.bootlin.com/linux/v6.10/source/drivers/gpio/gpio-ljca.c#L53.
```
struct ljca_gpio_packet {
u8 num;
struct ljca_gpio_op item[] __counted_by(num);
} __packed;
```
Our question is: The `item` member of `struct ljca_gpio_packet` is annotated with
"__counted_by". Only if we set `packet->num = 1` before accessing
`packet->item[0]`, the flexible member `item` can be properly bounds-checked at run-time
when enabling CONFIG_UBSAN_BOUNDS and CONFIG_FORTIFY_SOURCE. Or there will be a warning from
each access prior to the initialization because the number of elements is zero.
So we think relocating `packet->num = 1` before accessing `packet->item[0]` is
needed.
Here is a fix example of a similar situation :
https://lore.kernel.org/stable/[email protected]/.
Please kindly correct us if we missed any key information. Looking forward to
your response!
This is a Gustavo AR Silvia question, so let's loop him in.
(I think you're right, and we should make a patch.)
Yes! `packet->num = 1;` should be relocated:
diff --git a/drivers/gpio/gpio-ljca.c b/drivers/gpio/gpio-ljca.c
index dfec9fbfc7a9..c2a9b4253974 100644
--- a/drivers/gpio/gpio-ljca.c
+++ b/drivers/gpio/gpio-ljca.c
@@ -82,9 +82,9 @@ static int ljca_gpio_config(struct ljca_gpio_dev *ljca_gpio,
u8 gpio_id,
int ret;
mutex_lock(&ljca_gpio->trans_lock);
+ packet->num = 1;
packet->item[0].index = gpio_id;
packet->item[0].value = config | ljca_gpio->connect_mode[gpio_id];
- packet->num = 1;
ret = ljca_transfer(ljca_gpio->ljca, LJCA_GPIO_CONFIG, (u8 *)packet,
struct_size(packet, item, packet->num), NULL, 0);
stable should be CC'd and the following tag included:
Fixes: 1034cc423f1b ("1034cc423f1b4a7a9a56d310ca980fcd2753e11d")
Thanks for catching this! :)
--
Gustavo
