linux-kernel - Re: [PATCH v4] mm/hugetlb: Fix unsigned overflow in __nr_hugepages_store

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Date:   Tue, 26 Feb 2019 10:22:18 +0800
From:   Jing Xiangfeng <jingxiangfeng@...wei.com>
To:     David Rientjes <rientjes@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>
CC:     <mhocko@...nel.org>, <akpm@...ux-foundation.org>,
        <hughd@...gle.com>, <linux-mm@...ck.org>,
        <n-horiguchi@...jp.nec.com>, <aarcange@...hat.com>,
        <kirill.shutemov@...ux.intel.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] mm/hugetlb: Fix unsigned overflow in
 __nr_hugepages_store_common()

On 2019/2/26 3:17, David Rientjes wrote:
> On Mon, 25 Feb 2019, Mike Kravetz wrote:
> 
>> Ok, what about just moving the calculation/check inside the lock as in the
>> untested patch below?
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
>> ---
>>  mm/hugetlb.c | 34 ++++++++++++++++++++++++++--------
>>  1 file changed, 26 insertions(+), 8 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 1c5219193b9e..5afa77dc7bc8 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -2274,7 +2274,7 @@ static int adjust_pool_surplus(struct hstate *h,
>> nodemask_t *nodes_allowed,
>>  }
>>
>>  #define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
>> -static int set_max_huge_pages(struct hstate *h, unsigned long count,
>> +static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
>>  						nodemask_t *nodes_allowed)
>>  {
>>  	unsigned long min_count, ret;
>> @@ -2289,6 +2289,23 @@ static int set_max_huge_pages(struct hstate *h, unsigned
>> long count,
>>  		goto decrease_pool;
>>  	}
>>
>> +	spin_lock(&hugetlb_lock);
>> +
>> +	/*
>> +	 * Check for a node specific request.  Adjust global count, but
>> +	 * restrict alloc/free to the specified node.
>> +	 */
>> +	if (nid != NUMA_NO_NODE) {
>> +		unsigned long old_count = count;
>> +		count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
>> +		/*
>> +		 * If user specified count causes overflow, set to
>> +		 * largest possible value.
>> +		 */
>> +		if (count < old_count)
>> +			count = ULONG_MAX;
>> +	}
>> +
>>  	/*
>>  	 * Increase the pool size
>>  	 * First take pages out of surplus state.  Then make up the
>> @@ -2300,7 +2317,6 @@ static int set_max_huge_pages(struct hstate *h, unsigned
>> long count,
>>  	 * pool might be one hugepage larger than it needs to be, but
>>  	 * within all the constraints specified by the sysctls.
>>  	 */
>> -	spin_lock(&hugetlb_lock);
>>  	while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
>>  		if (!adjust_pool_surplus(h, nodes_allowed, -1))
>>  			break;
>> @@ -2421,16 +2437,18 @@ static ssize_t __nr_hugepages_store_common(bool
>> obey_mempolicy,
>>  			nodes_allowed = &node_states[N_MEMORY];
>>  		}
>>  	} else if (nodes_allowed) {
>> +		/* Node specific request */
>> +		init_nodemask_of_node(nodes_allowed, nid);
>> +	} else {
>>  		/*
>> -		 * per node hstate attribute: adjust count to global,
>> -		 * but restrict alloc/free to the specified node.
>> +		 * Node specific request, but we could not allocate
>> +		 * node mask.  Pass in ALL nodes, and clear nid.
>>  		 */
>> -		count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
>> -		init_nodemask_of_node(nodes_allowed, nid);
>> -	} else
>> +		nid = NUMA_NO_NODE;
>>  		nodes_allowed = &node_states[N_MEMORY];
>> +	}
>>
>> -	err = set_max_huge_pages(h, count, nodes_allowed);
>> +	err = set_max_huge_pages(h, count, nid, nodes_allowed);
>>  	if (err)
>>  		goto out;
>>
> 
> Looks good; Jing, could you test that this fixes your case?

Yes, I have tested this patch, it can also fix my case.
> 
> .
>