Commit 3d680bdf authored by Qian Cai's avatar Qian Cai Committed by Linus Torvalds
Browse files

mm/page_isolation: fix potential warning from user 

It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE)
from start_isolate_page_range(), but should avoid triggering it from
userspace, i.e, from is_mem_section_removable() because it could crash
the system by a non-root user if warn_on_panic is set.

While at it, simplify the code a bit by removing an unnecessary jump
label.

Link: http://lkml.kernel.org/r/20200120163915.1469-1-cai@lca.pw


Signed-off-by: default avatarQian Cai <cai@lca.pw>
Suggested-by: default avatarMichal Hocko <mhocko@kernel.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4a55c047

mm/page_alloc.c

+4 −7
Original line number Diff line number Diff line
@@ -8214,7 +8214,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
		if (is_migrate_cma(migratetype))

			return NULL;



		goto unmovable;

		return page;

	}



	for (; iter < pageblock_nr_pages; iter++) {
@@ -8224,7 +8224,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
		page = pfn_to_page(pfn + iter);



		if (PageReserved(page))

			goto unmovable;

			return page;



		/*

		 * If the zone is movable and we have ruled out all reserved
@@ -8244,7 +8244,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
			unsigned int skip_pages;



			if (!hugepage_migration_supported(page_hstate(head)))

				goto unmovable;

				return page;



			skip_pages = compound_nr(head) - (page - head);

			iter += skip_pages - 1;
@@ -8286,12 +8286,9 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, 
		 * is set to both of a memory hole page and a _used_ kernel

		 * page at boot.

		 */

		goto unmovable;

		return page;

	}

	return NULL;

unmovable:

	WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);

	return pfn_to_page(pfn + iter);

}



#ifdef CONFIG_CONTIG_ALLOC

mm/page_isolation.c

+11 −7
Original line number Diff line number Diff line
@@ -54,14 +54,18 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ 


out:

	spin_unlock_irqrestore(&zone->lock, flags);

	if (!ret)

	if (!ret) {

		drain_all_pages(zone);

	else if ((isol_flags & REPORT_FAILURE) && unmovable)

	} else {

		WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);



		if ((isol_flags & REPORT_FAILURE) && unmovable)

			/*

		 * printk() with zone->lock held will guarantee to trigger a

			 * printk() with zone->lock held will likely trigger a

			 * lockdep splat, so defer it here.

			 */

			dump_page(unmovable, "unmovable page");

	}



	return ret;

}

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