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hugetlb: remove use of list iterator variable after loop

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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: Jakob 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jakob Koschel 2022-04-28 23:16:03 -07:00 committed by akpm
parent b283d983a7
commit 84448c8ecd
1 changed files with 19 additions and 14 deletions
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33
mm/hugetlb.c
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@ -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);