On 22.10.19 19:12, David Hildenbrand wrote:
Right now, ZONE_DEVICE memory is always set PG_reserved. We want to change that. Let's make sure that the logic in the function won't change. Once we no longer set these pages to reserved, we can rework this function to perform separate checks for ZONE_DEVICE (split from PG_reserved checks). Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx> Cc: Allison Randal <allison@xxxxxxxxxxx> Cc: "Isaac J. Manjarres" <isaacm@xxxxxxxxxxxxxx> Cc: Qian Cai <cai@xxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> --- mm/usercopy.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index 660717a1ea5c..a3ac4be35cde 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -203,14 +203,15 @@ static inline void check_page_span(const void *ptr, unsigned long n, * device memory), or CMA. Otherwise, reject since the object spans * several independently allocated pages. */ - is_reserved = PageReserved(page); + is_reserved = PageReserved(page) || is_zone_device_page(page); is_cma = is_migrate_cma_page(page); if (!is_reserved && !is_cma) usercopy_abort("spans multiple pages", NULL, to_user, 0, n);for (ptr += PAGE_SIZE; ptr <= end; ptr += PAGE_SIZE) {page = virt_to_head_page(ptr); - if (is_reserved && !PageReserved(page)) + if (is_reserved && !(PageReserved(page) || + is_zone_device_page(page))) usercopy_abort("spans Reserved and non-Reserved pages", NULL, to_user, 0, n); if (is_cma && !is_migrate_cma_page(page))
@Kees, would it be okay to stop checking against ZONE_DEVICE pages here or is there a good rationale behind this?
(I would turn this patch into a simple update of the comment if we agree that we don't care)
-- Thanks, David / dhildenb
