Commit 6fae274c authored by Jackie Liu's avatar Jackie Liu Committed by Andrew Morton
Browse files

mm/mempolicy: fix memory leaks in weighted_interleave_auto_store() 

weighted_interleave_auto_store() fetches old_wi_state inside the if
(!input) block only.  This causes two memory leaks:

1. When a user writes "false" and the current mode is already manual,
   the function returns early without freeing the freshly allocated
   new_wi_state.

2. When a user writes "true", old_wi_state stays NULL because the
   fetch is skipped entirely. The old state is then overwritten by
   rcu_assign_pointer() but never freed, since the cleanup path is
   gated on old_wi_state being non-NULL. A user can trigger this
   repeatedly by writing "1" in a loop.

Fix both leaks by moving the old_wi_state fetch before the input check,
making it unconditional.  This also allows a unified early return for both
"true" and "false" when the requested mode matches the current mode.

Link: https://lore.kernel.org/20260401005702.7096-1-liu.yun@linux.dev
Link: https://sashiko.dev/#/patchset/20260331100740.84906-1-liu.yun@linux.dev


Fixes: e341f9c3 ("mm/mempolicy: Weighted Interleave Auto-tuning")
Signed-off-by: default avatarJackie Liu <liuyun01@kylinos.cn>
Reviewed-by: default avatarJoshua Hahn <joshua.hahnjy@gmail.com>
Reviewed by: Donet Tom <donettom@linux.ibm.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: <stable@vger.kernel.org> # v6.16+
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0c13ed77

mm/mempolicy.c

+12 −11
Original line number Diff line number Diff line
@@ -3700,16 +3700,17 @@ static ssize_t weighted_interleave_auto_store(struct kobject *kobj, 
		new_wi_state->iw_table[i] = 1;



	mutex_lock(&wi_state_lock);

	if (!input) {

	old_wi_state = rcu_dereference_protected(wi_state,

				lockdep_is_held(&wi_state_lock));

		if (!old_wi_state)

			goto update_wi_state;

		if (input == old_wi_state->mode_auto) {



	if (old_wi_state && input == old_wi_state->mode_auto) {

		mutex_unlock(&wi_state_lock);

		kfree(new_wi_state);

		return count;

	}



	if (!input) {

		if (old_wi_state)

			memcpy(new_wi_state->iw_table, old_wi_state->iw_table,

						       nr_node_ids * sizeof(u8));

		goto update_wi_state;