Commit 84448c8e authored by Jakob Koschel's avatar Jakob Koschel Committed by Andrew Morton
Browse files

hugetlb: remove use of list iterator variable after loop 

In preparation to limit the scope of the list iterator to the list
traversal loop, use a dedicated pointer to iterate through the list [1].

Before hugetlb_resv_map_add() was expecting a file_region struct, but in
case the list iterator in add_reservation_in_range() did not exit early,
the variable passed in, is not actually a valid structure.

In such a case 'rg' is computed on the head element of the list and
represents an out-of-bounds pointer.  This still remains safe *iff* you
only use the link member (as it is done in hugetlb_resv_map_add()).

To avoid the type-confusion altogether and limit the list iterator to the
loop, only a list_head pointer is kept to pass to hugetlb_resv_map_add().

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Link: https://lkml.kernel.org/r/20220331224323.903842-1-jakobkoschel@gmail.com


Signed-off-by: default avatarJakob Koschel <jakobkoschel@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "Brian Johannesmeyer" <bjohannesmeyer@gmail.com>
Cc: Cristiano Giuffrida <c.giuffrida@vu.nl>
Cc: "Bos, H.J." <h.j.bos@vu.nl>
Cc: Jakob Koschel <jakobkoschel@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b283d983

mm/hugetlb.c

+19 −14
Original line number Diff line number Diff line
@@ -370,7 +370,7 @@ static void coalesce_file_region(struct resv_map *resv, struct file_region *rg) 
}



static inline long

hugetlb_resv_map_add(struct resv_map *map, struct file_region *rg, long from,

hugetlb_resv_map_add(struct resv_map *map, struct list_head *rg, long from,

		     long to, struct hstate *h, struct hugetlb_cgroup *cg,

		     long *regions_needed)

{
@@ -379,7 +379,7 @@ hugetlb_resv_map_add(struct resv_map *map, struct file_region *rg, long from, 
	if (!regions_needed) {

		nrg = get_file_region_entry_from_cache(map, from, to);

		record_hugetlb_cgroup_uncharge_info(cg, h, map, nrg);

		list_add(&nrg->link, rg->link.prev);

		list_add(&nrg->link, rg);

		coalesce_file_region(map, nrg);

	} else

		*regions_needed += 1;
@@ -402,47 +402,52 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t, 
	long add = 0;

	struct list_head *head = &resv->regions;

	long last_accounted_offset = f;

	struct file_region *rg = NULL, *trg = NULL;

	struct file_region *iter, *trg = NULL;

	struct list_head *rg = NULL;



	if (regions_needed)

		*regions_needed = 0;



	/* In this loop, we essentially handle an entry for the range

	 * [last_accounted_offset, rg->from), at every iteration, with some

	 * [last_accounted_offset, iter->from), at every iteration, with some

	 * bounds checking.

	 */

	list_for_each_entry_safe(rg, trg, head, link) {

	list_for_each_entry_safe(iter, trg, head, link) {

		/* Skip irrelevant regions that start before our range. */

		if (rg->from < f) {

		if (iter->from < f) {

			/* If this region ends after the last accounted offset,

			 * then we need to update last_accounted_offset.

			 */

			if (rg->to > last_accounted_offset)

				last_accounted_offset = rg->to;

			if (iter->to > last_accounted_offset)

				last_accounted_offset = iter->to;

			continue;

		}



		/* When we find a region that starts beyond our range, we've

		 * finished.

		 */

		if (rg->from >= t)

		if (iter->from >= t) {

			rg = iter->link.prev;

			break;

		}



		/* Add an entry for last_accounted_offset -> rg->from, and

		/* Add an entry for last_accounted_offset -> iter->from, and

		 * update last_accounted_offset.

		 */

		if (rg->from > last_accounted_offset)

			add += hugetlb_resv_map_add(resv, rg,

		if (iter->from > last_accounted_offset)

			add += hugetlb_resv_map_add(resv, iter->link.prev,

						    last_accounted_offset,

						    rg->from, h, h_cg,

						    iter->from, h, h_cg,

						    regions_needed);



		last_accounted_offset = rg->to;

		last_accounted_offset = iter->to;

	}



	/* Handle the case where our range extends beyond

	 * last_accounted_offset.

	 */

	if (!rg)

		rg = head->prev;

	if (last_accounted_offset < t)

		add += hugetlb_resv_map_add(resv, rg, last_accounted_offset,

					    t, h, h_cg, regions_needed);