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gpiolib: don't allow userspace to set values of input lines

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User space can currently both read and set values of input lines using
the character device. This was not allowed by the old sysfs interface
nor is it a correct behavior.

Check the first descriptor in the set for the OUT flag when asked to
set values and return -EPERM if the line is input.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Bartosz Golaszewski 2018-07-16 10:34:23 +02:00 committed by Linus Walleij
parent ad81729741
commit e5332d5437
1 changed files with 7 additions and 1 deletions
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8
drivers/gpio/gpiolib.c
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@ -449,7 +449,13 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd,
return 0;
} else if (cmd == GPIOHANDLE_SET_LINE_VALUES_IOCTL) {
/* TODO: check if descriptors are really output */
/*
* All line descriptors were created at once with the same
* flags so just check if the first one is really output.
*/
if (!test_bit(FLAG_IS_OUT, &lh->descs[0]->flags))
return -EPERM;
if (copy_from_user(&ghd, ip, sizeof(ghd)))
return -EFAULT;