On Mon, 28 Mar 2022 at 03:09, Xiaomeng Tong xiam0nd.tong@gmail.com wrote:
on Sun, 27 Mar 2022 16:59:28 +0100, Emil Velikov wrote:
On Sun, 27 Mar 2022 at 08:39, Xiaomeng Tong xiam0nd.tong@gmail.com wrote:
The bug is here: return encoder;
The list iterator value 'encoder' will *always* be set and non-NULL by drm_for_each_encoder_mask(), so it is incorrect to assume that the iterator value will be NULL if the list is empty or no element found. Otherwise it will bypass some NULL checks and lead to invalid memory access passing the check.
To fix this bug, just return 'encoder' when found, otherwise return NULL.
Isn't this covered by the upcoming list* iterator rework [1] or is this another iterator glitch?
Actually, it is a part of the upcoming work.
IMHO we should be looking at fixing the implementation and not the hundreds of users through the kernel.
HTH -Emil [1] https://lwn.net/Articles/887097/
Yes, you are right. This has also been taken into account by the upcoming list iterator rework to avoid a lot uesr' changes as much as possible.
However, this patch is fixing a potential bug caused by incorrect use of list iterator outside the loop, which can not be fixed by the implementation itself.
I see, thanks for the information o/
-Emil