[RFC 1/2] mm, slub: prevent kmalloc_node crashes and memory leaks

[Vlastimil Babka]

On 3/20/20 4:42 AM, Bharata B Rao wrote:
> On Thu, Mar 19, 2020 at 02:47:58PM +0100, Vlastimil Babka wrote:
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 17dc00e33115..7113b1f9cd77 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1973,8 +1973,6 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
>>  
>>  	if (node == NUMA_NO_NODE)
>>  		searchnode = numa_mem_id();
>> -	else if (!node_present_pages(node))
>> -		searchnode = node_to_mem_node(node);
>>  
>>  	object = get_partial_node(s, get_node(s, searchnode), c, flags);
>>  	if (object || node != NUMA_NO_NODE)
>> @@ -2563,17 +2561,27 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>>  	struct page *page;
>>  
>>  	page = c->page;
>> -	if (!page)
>> +	if (!page) {
>> +		/*
>> +		 * if the node is not online or has no normal memory, just
>> +		 * ignore the node constraint
>> +		 */
>> +		if (unlikely(node != NUMA_NO_NODE &&
>> +			     !node_state(node, N_NORMAL_MEMORY)))
>> +			node = NUMA_NO_NODE;
>>  		goto new_slab;
>> +	}
>>  redo:
>>  
>>  	if (unlikely(!node_match(page, node))) {
>> -		int searchnode = node;
>> -
>> -		if (node != NUMA_NO_NODE && !node_present_pages(node))
>> -			searchnode = node_to_mem_node(node);
>> -
>> -		if (unlikely(!node_match(page, searchnode))) {
>> +		/*
>> +		 * same as above but node_match() being false already
>> +		 * implies node != NUMA_NO_NODE
>> +		 */
>> +		if (!node_state(node, N_NORMAL_MEMORY)) {
>> +			node = NUMA_NO_NODE;
>> +			goto redo;
>> +		} else {
>>  			stat(s, ALLOC_NODE_MISMATCH);
>>  			deactivate_slab(s, page, c->freelist, c);
>>  			goto new_slab;
> 
> This fixes the problem I reported at
> https://lore.kernel.org/linux-mm/20200317092624.GB22538@in.ibm.com/

Thanks, I hope it means I can make it Reported-and-tested-by: you