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@xxxxxxxxxxxxxx/ [1] Signed-off-by: Jakob Koschel <jakobkoschel@xxxxxxxxx> --- mm/hugetlb.c | 33 +++++++++++++++++++-------------- 1 file changed, 19 insertions(+), 14 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index b34f50156f7e..bb0cac980a0f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -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); base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275 -- 2.25.1
