Commit 08498be4 authored by Wei Yang's avatar Wei Yang Committed by Andrew Morton
Browse files

mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL 

Patch series "mm_slot: fix the usage of mm_slot_entry", v2.

When using mm_slot in ksm, there is code like:

     slot = mm_slot_lookup(mm_slots_hash, mm);
     mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
     if (mm_slot && ..) {
     }

The mm_slot_entry() won't return a valid value if slot is NULL generally. 
But currently it works since slot is the first element of struct
ksm_mm_slot.

To reduce the ambiguity and make it robust, access mm_slot_entry() when
slot is !NULL.

Link: https://lkml.kernel.org/r/20250919071244.17020-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20250919071244.17020-2-richard.weiyang@gmail.com


Signed-off-by: default avatarWei Yang <richard.weiyang@gmail.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarDev Jain <dev.jain@arm.com>
Reviewed-by: default avatarLance Yang <lance.yang@linux.dev>
Cc: Kiryl Shutsemau <kirill@shutemov.name>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 3dfd02c9

mm/ksm.c

+11 −9
Original line number Diff line number Diff line
@@ -2936,8 +2936,9 @@ void __ksm_exit(struct mm_struct *mm) 


	spin_lock(&ksm_mmlist_lock);

	slot = mm_slot_lookup(mm_slots_hash, mm);

	if (slot) {

		mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);

	if (mm_slot && ksm_scan.mm_slot != mm_slot) {

		if (ksm_scan.mm_slot != mm_slot) {

			if (!mm_slot->rmap_list) {

				hash_del(&slot->hash);

				list_del(&slot->mm_node);
@@ -2947,6 +2948,7 @@ void __ksm_exit(struct mm_struct *mm) 
					  &ksm_scan.mm_slot->slot.mm_node);

			}

		}

	}

	spin_unlock(&ksm_mmlist_lock);



	if (easy_to_free) {