2020-04-15 22:31:56

by Bartosz Golaszewski

Subject: [PATCH] gpiolib: improve the robustness of watch/unwatch ioctl()

From: Bartosz Golaszewski <[email protected]>

This makes the new ioctl() a bit more robust - we now check if a line
is already being watched and return -EBUSY if the user-space tries to
start watching it again. Same for unwatch - return -EBUSY if user-space
tries to unwatch a line that's not being watched.

Fixes: 51c1064e82e7 ("gpiolib: add new ioctl() for monitoring changes in line info")
Signed-off-by: Bartosz Golaszewski <[email protected]>
---
drivers/gpio/gpiolib.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 40f2d7f69be2..29f6abe84d2e 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1227,6 +1227,7 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
void __user *ip = (void __user *)arg;
struct gpio_desc *desc;
__u32 offset;
+ int hwgpio;

/* We fail any subsequent ioctl():s when the chip is gone */
if (!gc)
@@ -1259,13 +1260,19 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
if (IS_ERR(desc))
return PTR_ERR(desc);

+ hwgpio = gpio_chip_hwgpio(desc);
+
+ if (cmd == GPIO_GET_LINEINFO_WATCH_IOCTL &&
+ test_bit(hwgpio, priv->watched_lines))
+ return -EBUSY;
+
gpio_desc_to_lineinfo(desc, &lineinfo);

if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
return -EFAULT;

if (cmd == GPIO_GET_LINEINFO_WATCH_IOCTL)
- set_bit(gpio_chip_hwgpio(desc), priv->watched_lines);
+ set_bit(hwgpio, priv->watched_lines);

return 0;
} else if (cmd == GPIO_GET_LINEHANDLE_IOCTL) {
@@ -1280,7 +1287,12 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
if (IS_ERR(desc))
return PTR_ERR(desc);

- clear_bit(gpio_chip_hwgpio(desc), priv->watched_lines);
+ hwgpio = gpio_chip_hwgpio(desc);
+
+ if (!test_bit(hwgpio, priv->watched_lines))
+ return -EBUSY;
+
+ clear_bit(hwgpio, priv->watched_lines);
return 0;
}
return -EINVAL;
--
2.25.0

2020-04-16 11:39:27

by Linus Walleij

Subject: Re: [PATCH] gpiolib: improve the robustness of watch/unwatch ioctl()

On Wed, Apr 15, 2020 at 10:24 AM Bartosz Golaszewski <[email protected]> wrote:

> From: Bartosz Golaszewski <[email protected]>
>
> This makes the new ioctl() a bit more robust - we now check if a line
> is already being watched and return -EBUSY if the user-space tries to
> start watching it again. Same for unwatch - return -EBUSY if user-space
> tries to unwatch a line that's not being watched.
>
> Fixes: 51c1064e82e7 ("gpiolib: add new ioctl() for monitoring changes in line info")
> Signed-off-by: Bartosz Golaszewski <[email protected]>

Reviewed-by: Linus Walleij <[email protected]>

I expect that you send me a pull request with some GPIO fixes
when you feel you have some stuff including this I should send
upstream, thanks!

Yours,
Linus Walleij