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![Haimin Zhang](/assets/img/avatar_default.png)
Without it, kernel crashes in map_get_next_key().
Fixes: 9330986c03
("bpf: Add bloom filter map implementation")
Reported-by: TCS Robot <tcs_robot@tencent.com>
Signed-off-by: Haimin Zhang <tcs_kernel@tencent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Joanne Koong <joannekoong@fb.com>
Link: https://lore.kernel.org/bpf/1640776802-22421-1-git-send-email-tcs.kernel@gmail.com
210 lines
5.6 KiB
C
210 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2021 Facebook */
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#include <linux/bitmap.h>
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#include <linux/bpf.h>
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#include <linux/btf.h>
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#include <linux/err.h>
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#include <linux/jhash.h>
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#include <linux/random.h>
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#define BLOOM_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_ZERO_SEED | BPF_F_ACCESS_MASK)
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struct bpf_bloom_filter {
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struct bpf_map map;
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u32 bitset_mask;
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u32 hash_seed;
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/* If the size of the values in the bloom filter is u32 aligned,
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* then it is more performant to use jhash2 as the underlying hash
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* function, else we use jhash. This tracks the number of u32s
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* in an u32-aligned value size. If the value size is not u32 aligned,
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* this will be 0.
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*/
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u32 aligned_u32_count;
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u32 nr_hash_funcs;
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unsigned long bitset[];
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};
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static u32 hash(struct bpf_bloom_filter *bloom, void *value,
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u32 value_size, u32 index)
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{
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u32 h;
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if (bloom->aligned_u32_count)
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h = jhash2(value, bloom->aligned_u32_count,
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bloom->hash_seed + index);
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else
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h = jhash(value, value_size, bloom->hash_seed + index);
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return h & bloom->bitset_mask;
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}
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static int bloom_map_peek_elem(struct bpf_map *map, void *value)
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{
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struct bpf_bloom_filter *bloom =
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container_of(map, struct bpf_bloom_filter, map);
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u32 i, h;
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for (i = 0; i < bloom->nr_hash_funcs; i++) {
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h = hash(bloom, value, map->value_size, i);
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if (!test_bit(h, bloom->bitset))
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return -ENOENT;
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}
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return 0;
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}
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static int bloom_map_push_elem(struct bpf_map *map, void *value, u64 flags)
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{
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struct bpf_bloom_filter *bloom =
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container_of(map, struct bpf_bloom_filter, map);
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u32 i, h;
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if (flags != BPF_ANY)
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return -EINVAL;
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for (i = 0; i < bloom->nr_hash_funcs; i++) {
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h = hash(bloom, value, map->value_size, i);
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set_bit(h, bloom->bitset);
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}
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return 0;
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}
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static int bloom_map_pop_elem(struct bpf_map *map, void *value)
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{
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return -EOPNOTSUPP;
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}
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static int bloom_map_delete_elem(struct bpf_map *map, void *value)
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{
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return -EOPNOTSUPP;
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}
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static int bloom_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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{
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return -EOPNOTSUPP;
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}
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static struct bpf_map *bloom_map_alloc(union bpf_attr *attr)
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{
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u32 bitset_bytes, bitset_mask, nr_hash_funcs, nr_bits;
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int numa_node = bpf_map_attr_numa_node(attr);
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struct bpf_bloom_filter *bloom;
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if (!bpf_capable())
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return ERR_PTR(-EPERM);
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if (attr->key_size != 0 || attr->value_size == 0 ||
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attr->max_entries == 0 ||
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attr->map_flags & ~BLOOM_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags) ||
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/* The lower 4 bits of map_extra (0xF) specify the number
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* of hash functions
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*/
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(attr->map_extra & ~0xF))
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return ERR_PTR(-EINVAL);
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nr_hash_funcs = attr->map_extra;
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if (nr_hash_funcs == 0)
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/* Default to using 5 hash functions if unspecified */
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nr_hash_funcs = 5;
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/* For the bloom filter, the optimal bit array size that minimizes the
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* false positive probability is n * k / ln(2) where n is the number of
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* expected entries in the bloom filter and k is the number of hash
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* functions. We use 7 / 5 to approximate 1 / ln(2).
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*
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* We round this up to the nearest power of two to enable more efficient
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* hashing using bitmasks. The bitmask will be the bit array size - 1.
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*
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* If this overflows a u32, the bit array size will have 2^32 (4
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* GB) bits.
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*/
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if (check_mul_overflow(attr->max_entries, nr_hash_funcs, &nr_bits) ||
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check_mul_overflow(nr_bits / 5, (u32)7, &nr_bits) ||
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nr_bits > (1UL << 31)) {
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/* The bit array size is 2^32 bits but to avoid overflowing the
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* u32, we use U32_MAX, which will round up to the equivalent
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* number of bytes
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*/
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bitset_bytes = BITS_TO_BYTES(U32_MAX);
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bitset_mask = U32_MAX;
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} else {
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if (nr_bits <= BITS_PER_LONG)
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nr_bits = BITS_PER_LONG;
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else
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nr_bits = roundup_pow_of_two(nr_bits);
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bitset_bytes = BITS_TO_BYTES(nr_bits);
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bitset_mask = nr_bits - 1;
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}
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bitset_bytes = roundup(bitset_bytes, sizeof(unsigned long));
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bloom = bpf_map_area_alloc(sizeof(*bloom) + bitset_bytes, numa_node);
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if (!bloom)
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return ERR_PTR(-ENOMEM);
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bpf_map_init_from_attr(&bloom->map, attr);
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bloom->nr_hash_funcs = nr_hash_funcs;
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bloom->bitset_mask = bitset_mask;
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/* Check whether the value size is u32-aligned */
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if ((attr->value_size & (sizeof(u32) - 1)) == 0)
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bloom->aligned_u32_count =
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attr->value_size / sizeof(u32);
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if (!(attr->map_flags & BPF_F_ZERO_SEED))
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bloom->hash_seed = get_random_int();
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return &bloom->map;
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}
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static void bloom_map_free(struct bpf_map *map)
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{
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struct bpf_bloom_filter *bloom =
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container_of(map, struct bpf_bloom_filter, map);
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bpf_map_area_free(bloom);
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}
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static void *bloom_map_lookup_elem(struct bpf_map *map, void *key)
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{
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/* The eBPF program should use map_peek_elem instead */
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return ERR_PTR(-EINVAL);
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}
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static int bloom_map_update_elem(struct bpf_map *map, void *key,
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void *value, u64 flags)
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{
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/* The eBPF program should use map_push_elem instead */
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return -EINVAL;
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}
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static int bloom_map_check_btf(const struct bpf_map *map,
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const struct btf *btf,
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const struct btf_type *key_type,
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const struct btf_type *value_type)
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{
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/* Bloom filter maps are keyless */
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return btf_type_is_void(key_type) ? 0 : -EINVAL;
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}
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static int bpf_bloom_map_btf_id;
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const struct bpf_map_ops bloom_filter_map_ops = {
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.map_meta_equal = bpf_map_meta_equal,
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.map_alloc = bloom_map_alloc,
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.map_free = bloom_map_free,
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.map_get_next_key = bloom_map_get_next_key,
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.map_push_elem = bloom_map_push_elem,
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.map_peek_elem = bloom_map_peek_elem,
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.map_pop_elem = bloom_map_pop_elem,
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.map_lookup_elem = bloom_map_lookup_elem,
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.map_update_elem = bloom_map_update_elem,
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.map_delete_elem = bloom_map_delete_elem,
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.map_check_btf = bloom_map_check_btf,
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.map_btf_name = "bpf_bloom_filter",
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.map_btf_id = &bpf_bloom_map_btf_id,
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};
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