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| author |   Daniel Borkmann <daniel@iogearbox.net> | 2018-11-20 00:53:40 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-11-20 00:53:41 +0100 |
| commit | bbe5d311be6624d15df1d060094cfcb3259f3ccd (patch) | |
| tree | d134d18f7e5d8932d474d5765ed07b051fc31360 /kernel | |
| parent | bpf: libbpf: retry map creation without the name (diff) | |
| parent | tools: add selftest for BPF_F_ZERO_SEED (diff) | |
| download | linux-dev-bbe5d311be6624d15df1d060094cfcb3259f3ccd.tar.xz linux-dev-bbe5d311be6624d15df1d060094cfcb3259f3ccd.zip | |
Merge branch 'bpf-zero-hash-seed'
Lorenz Bauer says:
====================
Allow forcing the seed of a hash table to zero, for deterministic
execution during benchmarking and testing.
Changes from v2:
* Change ordering of BPF_F_ZERO_SEED in linux/bpf.h
Comments adressed from v1:
* Add comment to discourage production use to linux/bpf.h
* Require CAP_SYS_ADMIN
====================
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/hashtab.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 2c1790288138..4b7c76765d9d 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -23,7 +23,7 @@ #define HTAB_CREATE_FLAG_MASK \ (BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU | BPF_F_NUMA_NODE | \ - BPF_F_RDONLY | BPF_F_WRONLY) + BPF_F_RDONLY | BPF_F_WRONLY | BPF_F_ZERO_SEED) struct bucket { struct hlist_nulls_head head; @@ -244,6 +244,7 @@ static int htab_map_alloc_check(union bpf_attr *attr) */ bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU); bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC); + bool zero_seed = (attr->map_flags & BPF_F_ZERO_SEED); int numa_node = bpf_map_attr_numa_node(attr); BUILD_BUG_ON(offsetof(struct htab_elem, htab) != @@ -257,6 +258,10 @@ static int htab_map_alloc_check(union bpf_attr *attr) */ return -EPERM; + if (zero_seed && !capable(CAP_SYS_ADMIN)) + /* Guard against local DoS, and discourage production use. */ + return -EPERM; + if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK) /* reserved bits should not be used */ return -EINVAL; @@ -373,7 +378,11 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) if (!htab->buckets) goto free_htab; - htab->hashrnd = get_random_int(); + if (htab->map.map_flags & BPF_F_ZERO_SEED) + htab->hashrnd = 0; + else + htab->hashrnd = get_random_int(); + for (i = 0; i < htab->n_buckets; i++) { INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i); raw_spin_lock_init(&htab->buckets[i].lock); |