Commit 54fc2dfe authored by Liu Shixin's avatar Liu Shixin
Browse files

memcg: fix incorrect value of sysctl_memcg_swap_qos_stat 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9NC0J


CVE: NA

--------------------------------

The function sysctl_memcg_swap_qos_handler() doesn't handle error case
correctly and care nothing about concurrency. To fix it, we should do two
thing:

 1. reset sysctl_memcg_swap_qos_stat to old value for error case.
 2. add a mutex_lock to protect the process.

Fixes: 8202acc6 ("memcg/swap: add ability to disable memcg swap")
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 3a4c6550

mm/memcontrol.c

+20 −11
Original line number Diff line number Diff line
@@ -4095,22 +4095,21 @@ static int sysctl_memcg_swap_qos_handler(struct ctl_table *table, int write, 
			void __user *buffer, size_t *length, loff_t *ppos)

{

	int ret;

	int qos_stat_old = sysctl_memcg_swap_qos_stat;

	int qos_stat_old;

	int swap_type;

	static DEFINE_MUTEX(sysctl_mutex);



	mutex_lock(&sysctl_mutex);

	qos_stat_old = sysctl_memcg_swap_qos_stat;

	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);

	if (ret)

		return ret;



	if (write && !ret) {

		if (qos_stat_old == sysctl_memcg_swap_qos_stat)

		return 0;



	if (write) {

			goto unlock;



		switch (sysctl_memcg_swap_qos_stat) {

		case MEMCG_SWAP_STAT_DISABLE:

			static_branch_disable(&memcg_swap_qos_key);

			return 0;

			goto unlock;

		case MEMCG_SWAP_STAT_ALL:

			swap_type = SWAP_TYPE_ALL;

			break;
@@ -4119,16 +4118,26 @@ static int sysctl_memcg_swap_qos_handler(struct ctl_table *table, int write, 
			break;

		}



		/*

		 * Enable the feature when it is in disabled state.

		 * If it is already in enabled state, don't allowed

		 * to switch it to other state directly since it is

		 * dangerous that will impact all memory cgroups.

		 */

		if (!qos_stat_old) {

			memcg_swap_qos_reset(swap_type);

			static_branch_enable(&memcg_swap_qos_key);

			enable_swap_slots_cache_max();

		} else {

			return -EINVAL;

			sysctl_memcg_swap_qos_stat = qos_stat_old;

			ret = -EINVAL;

		}

	}



	return 0;

unlock:

	mutex_unlock(&sysctl_mutex);



	return ret;

}



static struct ctl_table memcg_swap_qos_sysctls[] = {