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| author |   Alexei Starovoitov <ast@kernel.org> | 2019-11-14 10:57:14 -0800 |
|---|---|---|
| committer |   Daniel Borkmann <daniel@iogearbox.net> | 2019-11-15 23:44:20 +0100 |
| commit | 9cc31b3a092d9bf2a18f09ad77e727ddb42a5b1e (patch) | |
| tree | 36be1bd2c248be20e0688560b3b678357807444e /kernel | |
| parent | bpf: Reserve space for BPF trampoline in BPF programs (diff) | |
| download | linux-dev-9cc31b3a092d9bf2a18f09ad77e727ddb42a5b1e.tar.xz linux-dev-9cc31b3a092d9bf2a18f09ad77e727ddb42a5b1e.zip | |
bpf: Fix race in btf_resolve_helper_id()
btf_resolve_helper_id() caching logic is a bit racy, since under root the
verifier can verify several programs in parallel. Fix it with READ/WRITE_ONCE.
Fix the type as well, since error is also recorded.
Fixes: a7658e1a4164 ("bpf: Check types of arguments passed into helpers")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-15-ast@kernel.org
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/btf.c | 26 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 8 |
2 files changed, 28 insertions, 6 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 9e1164e5b429..033d071eb59c 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3721,7 +3721,8 @@ again: return -EINVAL; } -u32 btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, int arg) +static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, + int arg) { char fnname[KSYM_SYMBOL_LEN + 4] = "btf_"; const struct btf_param *args; @@ -3789,6 +3790,29 @@ u32 btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn, int arg) return btf_id; } +int btf_resolve_helper_id(struct bpf_verifier_log *log, + const struct bpf_func_proto *fn, int arg) +{ + int *btf_id = &fn->btf_id[arg]; + int ret; + + if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID) + return -EINVAL; + + ret = READ_ONCE(*btf_id); + if (ret) + return ret; + /* ok to race the search. The result is the same */ + ret = __btf_resolve_helper_id(log, fn->func, arg); + if (!ret) { + /* Function argument cannot be type 'void' */ + bpf_log(log, "BTF resolution bug\n"); + return -EFAULT; + } + WRITE_ONCE(*btf_id, ret); + return ret; +} + static int __get_type_size(struct btf *btf, u32 btf_id, const struct btf_type **bad_type) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8f89cfa93e88..e78ec7990767 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4147,11 +4147,9 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn meta.func_id = func_id; /* check args */ for (i = 0; i < 5; i++) { - if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID) { - if (!fn->btf_id[i]) - fn->btf_id[i] = btf_resolve_helper_id(&env->log, fn->func, i); - meta.btf_id = fn->btf_id[i]; - } + err = btf_resolve_helper_id(&env->log, fn, i); + if (err > 0) + meta.btf_id = err; err = check_func_arg(env, BPF_REG_1 + i, fn->arg_type[i], &meta); if (err) return err; |