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.

[2] https://lore.kernel.org/stable/20260505094529.406783-1-dmantipov@yandex.ru/T/#u

Suggested-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>