Re: [PATCH] lib: free pagelist on error in iov_iter_extract_pages()

[Andrew Morton <akpm@linux-foundation.org>]

On Fri,  8 May 2026 14:13:29 +0300 Dmitry Antipov <dmantipov@yandex.ru> wrote:

> Since 'iov_iter_extract_pages()' may allocate new pagelist if the passed
> one isn't large enough, the worst-case scenario may be:
> 
> ...
> struct page *stack_pages[SMALL];
> struct page **pages = stack_pages;
> ...
> if (iov_iter_extract_pages(i..., &pages, ...) <= 0) {
>         /* Even in case of error, new pagelist may be allocated */
>         if (pages != stack_pages)
>                 kvfree(pages);                                  [1]
>         /* The rest of error handling and return */
> }
> /* Regular flow */
> ...
> if (pages != stack_pages)
>         kvfree(pages);
> ...
> return 0;
> 
> If you're unlucky so SMALL amount of pages wasn't enough and new
> pagelist was allocated, missing [1] causes the memory leak similar
> to one I've recently observed and fixed for 6.12 in [2]. So adjust
> 'iov_iter_extract_pages()' to make such a cleanup itself rather than
> rely on caller's handling on error paths, thus making [1] not needed.

AI review said things:
	https://sashiko.dev/#/patchset/20260508111329.329943-1-dmantipov@yandex.ru