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SubjectRe: [PATCH] watchdog: avoid usage of iterator after loop
From
On 3/1/23 09:17, Jakob Koschel wrote:
> 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 marcro to avoid any potential misuse after

macro

> the loop [1].
>
> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
> Signed-off-by: Jakob Koschel <jkl820.git@gmail.com>
> ---
> drivers/watchdog/watchdog_pretimeout.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/watchdog/watchdog_pretimeout.c b/drivers/watchdog/watchdog_pretimeout.c
> index 376a495ab80c..d8c78696eaf5 100644
> --- a/drivers/watchdog/watchdog_pretimeout.c
> +++ b/drivers/watchdog/watchdog_pretimeout.c
> @@ -207,10 +207,10 @@ 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);
> - break;
> + spin_unlock_irq(&pretimeout_lock);
> + kfree(p);
> + return;

Please just make it
kfree(p);
break;

There is no need to drop the spinlock here and/or to return
directly.

Thanks,
Guenter

> }
> }
> spin_unlock_irq(&pretimeout_lock);
> -
> - kfree(p);
> }
>
> ---
> base-commit: c0927a7a5391f7d8e593e5e50ead7505a23cadf9
> change-id: 20230301-watchdog-avoid-iter-after-loop-a197bf201435
>
> Best regards,

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