Patch "gpiolib: cdev: Ignore reconfiguration without direction" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    gpiolib: cdev: Ignore reconfiguration without direction

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     gpiolib-cdev-ignore-reconfiguration-without-directio.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 1eb6d71d441d2959ea98e7fc42cc310f6af90e24
Author: Kent Gibson <warthog618@xxxxxxxxx>
Date:   Wed Jun 26 13:29:23 2024 +0800

    gpiolib: cdev: Ignore reconfiguration without direction
    
    [ Upstream commit b440396387418fe2feaacd41ca16080e7a8bc9ad ]
    
    linereq_set_config() behaves badly when direction is not set.
    The configuration validation is borrowed from linereq_create(), where,
    to verify the intent of the user, the direction must be set to in order to
    effect a change to the electrical configuration of a line. But, when
    applied to reconfiguration, that validation does not allow for the unset
    direction case, making it possible to clear flags set previously without
    specifying the line direction.
    
    Adding to the inconsistency, those changes are not immediately applied by
    linereq_set_config(), but will take effect when the line value is next get
    or set.
    
    For example, by requesting a configuration with no flags set, an output
    line with GPIO_V2_LINE_FLAG_ACTIVE_LOW and GPIO_V2_LINE_FLAG_OPEN_DRAIN
    set could have those flags cleared, inverting the sense of the line and
    changing the line drive to push-pull on the next line value set.
    
    Skip the reconfiguration of lines for which the direction is not set, and
    only reconfigure the lines for which direction is set.
    
    Fixes: a54756cb24ea ("gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL")
    Signed-off-by: Kent Gibson <warthog618@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20240626052925.174272-3-warthog618@xxxxxxxxx
    Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 04261adf320b8..5639abce6ec57 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -1534,12 +1534,14 @@ static long linereq_set_config(struct linereq *lr, void __user *ip)
 		line = &lr->lines[i];
 		desc = lr->lines[i].desc;
 		flags = gpio_v2_line_config_flags(&lc, i);
-		gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags);
-		edflags = flags & GPIO_V2_LINE_EDGE_DETECTOR_FLAGS;
 		/*
-		 * Lines have to be requested explicitly for input
-		 * or output, else the line will be treated "as is".
+		 * Lines not explicitly reconfigured as input or output
+		 * are left unchanged.
 		 */
+		if (!(flags & GPIO_V2_LINE_DIRECTION_FLAGS))
+			continue;
+		gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags);
+		edflags = flags & GPIO_V2_LINE_EDGE_DETECTOR_FLAGS;
 		if (flags & GPIO_V2_LINE_FLAG_OUTPUT) {
 			int val = gpio_v2_line_config_output_value(&lc, i);
 
@@ -1547,7 +1549,7 @@ static long linereq_set_config(struct linereq *lr, void __user *ip)
 			ret = gpiod_direction_output(desc, val);
 			if (ret)
 				return ret;
-		} else if (flags & GPIO_V2_LINE_FLAG_INPUT) {
+		} else {
 			ret = gpiod_direction_input(desc);
 			if (ret)
 				return ret;