4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Bartosz Golaszewski <brgl@xxxxxxxx>
[ Upstream commit e5332d5437764f775cf4e3b8ca3bf592af063a02 ]
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@xxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpio/gpiolib.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -449,7 +449,13 @@ static long linehandle_ioctl(struct file
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;
