Commit c502faf9 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf, lpm: fix overflows in trie_alloc checks 



Cap the maximum (total) value size and bail out if larger than KMALLOC_MAX_SIZE
as otherwise it doesn't make any sense to proceed further, since we're
guaranteed to fail to allocate elements anyway in lpm_trie_node_alloc();
likleyhood of failure is still high for large values, though, similarly
as with htab case in non-prealloc.

Next, make sure that cost vars are really u64 instead of size_t, so that we
don't overflow on 32 bit and charge only tiny map.pages against memlock while
allowing huge max_entries; cap also the max cost like we do with other map
types.

Fixes: b95a5c4d ("bpf: add a longest prefix match trie map implementation")
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8ef95947

kernel/bpf/lpm_trie.c

+27 −9
Original line number Diff line number Diff line
@@ -394,10 +394,21 @@ static int trie_delete_elem(struct bpf_map *map, void *key) 
	return -ENOSYS;

}



#define LPM_DATA_SIZE_MAX	256

#define LPM_DATA_SIZE_MIN	1



#define LPM_VAL_SIZE_MAX	(KMALLOC_MAX_SIZE - LPM_DATA_SIZE_MAX - \

				 sizeof(struct lpm_trie_node))

#define LPM_VAL_SIZE_MIN	1



#define LPM_KEY_SIZE(X)		(sizeof(struct bpf_lpm_trie_key) + (X))

#define LPM_KEY_SIZE_MAX	LPM_KEY_SIZE(LPM_DATA_SIZE_MAX)

#define LPM_KEY_SIZE_MIN	LPM_KEY_SIZE(LPM_DATA_SIZE_MIN)



static struct bpf_map *trie_alloc(union bpf_attr *attr)

{

	size_t cost, cost_per_node;

	struct lpm_trie *trie;

	u64 cost = sizeof(*trie), cost_per_node;

	int ret;



	if (!capable(CAP_SYS_ADMIN))
@@ -406,9 +417,10 @@ static struct bpf_map *trie_alloc(union bpf_attr *attr) 
	/* check sanity of attributes */

	if (attr->max_entries == 0 ||

	    attr->map_flags != BPF_F_NO_PREALLOC ||

	    attr->key_size < sizeof(struct bpf_lpm_trie_key) + 1   ||

	    attr->key_size > sizeof(struct bpf_lpm_trie_key) + 256 ||

	    attr->value_size == 0)

	    attr->key_size < LPM_KEY_SIZE_MIN ||

	    attr->key_size > LPM_KEY_SIZE_MAX ||

	    attr->value_size < LPM_VAL_SIZE_MIN ||

	    attr->value_size > LPM_VAL_SIZE_MAX)

		return ERR_PTR(-EINVAL);



	trie = kzalloc(sizeof(*trie), GFP_USER | __GFP_NOWARN);
@@ -426,18 +438,24 @@ static struct bpf_map *trie_alloc(union bpf_attr *attr) 


	cost_per_node = sizeof(struct lpm_trie_node) +

			attr->value_size + trie->data_size;

	cost = sizeof(*trie) + attr->max_entries * cost_per_node;

	cost += (u64) attr->max_entries * cost_per_node;

	if (cost >= U32_MAX - PAGE_SIZE) {

		ret = -E2BIG;

		goto out_err;

	}



	trie->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;



	ret = bpf_map_precharge_memlock(trie->map.pages);

	if (ret) {

		kfree(trie);

		return ERR_PTR(ret);

	}

	if (ret)

		goto out_err;



	raw_spin_lock_init(&trie->lock);



	return &trie->map;

out_err:

	kfree(trie);

	return ERR_PTR(ret);

}



static void trie_free(struct bpf_map *map)

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