gpiolib: cdev: fix null pointer dereference in linereq_free()

Fix a kernel NULL pointer dereference reported by gpio kselftests.

linereq_free() can be called as part of the cleanup of a failed request,
at which time the desc for a line may not have been determined, so it
is unsafe to dereference without a check.

Add a check prior to dereferencing the line desc.

Fixes: 2068339a6c35 ("gpiolib: cdev: Add hardware timestamp clock type")
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index f5aa5f9..0c9a63b 100644 (file)
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -1460,11 +1460,12 @@ static ssize_t linereq_read(struct file *file,
 static void linereq_free(struct linereq *lr)
 {
        unsigned int i;
-       bool hte;
+       bool hte = false;
 
        for (i = 0; i < lr->num_lines; i++) {
-               hte = !!test_bit(FLAG_EVENT_CLOCK_HTE,
-                                &lr->lines[i].desc->flags);
+               if (lr->lines[i].desc)
+                       hte = !!test_bit(FLAG_EVENT_CLOCK_HTE,
+                                        &lr->lines[i].desc->flags);
                edge_detector_stop(&lr->lines[i], hte);
                if (lr->lines[i].desc)
                        gpiod_free(lr->lines[i].desc);