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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: b95a5c4db0 ("bpf: add a longest prefix match trie map implementation")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2017-02-08 01:19:43 +01:00 committed by David S. Miller
parent 8ef9594764
commit c502faf941
1 changed files with 27 additions and 9 deletions
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36
kernel/bpf/lpm_trie.c
View File

@ -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)