watchdog: avoid usage of iterator after loop

If potentially no valid element is found, 'p' would contain an invalid
pointer past the iterator loop. To ensure 'p' is valid under any
circumstances, the kfree() should be within the loop body.

Additionally, Linus proposed to avoid any use of the list iterator
variable after the loop, in the attempt to move the list iterator
variable declaration into the macro to avoid any potential misuse after
the loop [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
Signed-off-by: Jakob Koschel <jkl820.git@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230301-watchdog-avoid-iter-after-loop-v2-1-8411e3bbe0de@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

diff --git a/drivers/watchdog/watchdog_pretimeout.c b/drivers/watchdog/watchdog_pretimeout.c
index 376a495ab80c498bb0ccd9e18deb006b39b552bb..e5295c990fa1b8a0df328811fb061b03520da02b 100644 (file)
--- a/drivers/watchdog/watchdog_pretimeout.c
+++ b/drivers/watchdog/watchdog_pretimeout.c
@@ -207,10 +207,9 @@ void watchdog_unregister_pretimeout(struct watchdog_device *wdd)
        list_for_each_entry_safe(p, t, &pretimeout_list, entry) {
                if (p->wdd == wdd) {
                        list_del(&p->entry);
+                       kfree(p);
                        break;
                }
        }
        spin_unlock_irq(&pretimeout_lock);
-
-       kfree(p);
 }