Re: [PATCH bpf-next 01/10] bpf: btf: Introduce BPF Type Format (BTF)
flat view
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2018-03-30 23:22:55
On 03/30/2018 08:26 PM, Martin KaFai Lau wrote: [...]
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+static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t) +{ + struct btf *btf = env->btf; + + /* < 2 because +1 for btf_void which is always in btf->types[0]. + * btf_void is not accounted in btf->nr_types because btf_void + * does not come from the BTF file. + */ + if (btf->types_size - btf->nr_types < 2) { + /* Expand 'types' array */ + + struct btf_type **new_types; + u32 expand_by, new_size; + + if (btf->types_size == BTF_MAX_NR_TYPES) { + btf_verifier_log(env, "Exceeded max num of types"); + return -E2BIG; + } + + expand_by = max_t(u32, btf->types_size >> 2, 16); + new_size = min_t(u32, BTF_MAX_NR_TYPES, + btf->types_size + expand_by); + + new_types = kvzalloc(new_size * sizeof(*new_types), + GFP_KERNEL | __GFP_NOWARN); + if (!new_types) + return -ENOMEM; + + if (btf->nr_types == 0) + new_types[0] = &btf_void; + else + memcpy(new_types, btf->types, + sizeof(*btf->types) * (btf->nr_types + 1)); + + kfree(btf->types); + btf->types = new_types;
Haven't read through the whole series yet, but this type of pattern pops up immediately in several locations throughout multiple patches in this series. Here, you'll free kv*alloc() backed memory into the wrong backend allocator, thus if it's vmalloc() backed, it cannot go into kmalloc() backed memory via kfree(), thus please audit the whole series on this.
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+ btf->types_size = new_size; + } + + btf->types[++(btf->nr_types)] = t; + + return 0; +} + +static void btf_free(struct btf *btf) +{ + kfree(btf->types); + kfree(btf->data); + kfree(btf); +} + +static void btf_verifier_env_free(struct btf_verifier_env *env) +{ + kfree(env); +} +
[...]
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+ data = kvmalloc(btf_data_size, GFP_KERNEL | __GFP_NOWARN); + if (!data) { + err = -ENOMEM; + goto errout; + } + + btf->data = data; + btf->data_size = btf_data_size; + + if (copy_from_user(data, btf_data, btf_data_size)) { + err = -EFAULT; + goto errout; + } + + env->btf = btf; + + err = btf_parse_hdr(env); + if (err) + goto errout; + + err = btf_parse_str_sec(env); + if (err) + goto errout; + + err = btf_parse_type_sec(env); + if (err) + goto errout; + + if (!err && log->level && bpf_verifier_log_full(log)) { + err = -ENOSPC; + goto errout; + } + + if (!err) { + btf_verifier_env_free(env); + return btf; + } + +errout: + btf_verifier_env_free(env); + if (btf) + btf_free(btf); + return ERR_PTR(err); +}