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: b95a5c4db09b ("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>

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index 144e9763102fb3382a068bfc6592525a4085b1f0..e0f6a0bd279b8a8c8b681bdfa6d961ac78e3630a 100644 (file)
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -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)