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

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;