From 13a27dfc669724564aafa2699976ee756029fed2 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 21 Sep 2016 11:43:58 +0100 Subject: [PATCH] bpf: enable non-core use of the verfier Advanced JIT compilers and translators may want to use eBPF verifier as a base for parsers or to perform custom checks and validations. Add ability for external users to invoke the verifier and provide callbacks to be invoked for every intruction checked. For now only add most basic callback for per-instruction pre-interpretation checks is added. More advanced users may also like to have per-instruction post callback and state comparison callback. Signed-off-by: Jakub Kicinski Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- include/linux/bpf_verifier.h | 11 ++++++ kernel/bpf/verifier.c | 68 ++++++++++++++++++++++++++++++++++++ 2 files changed, 79 insertions(+) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 9457a22fc6e0..c5cb661712c9 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -59,6 +59,12 @@ struct bpf_insn_aux_data { #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ +struct bpf_verifier_env; +struct bpf_ext_analyzer_ops { + int (*insn_hook)(struct bpf_verifier_env *env, + int insn_idx, int prev_insn_idx); +}; + /* single container for all structs * one verifier_env per bpf_check() call */ @@ -68,6 +74,8 @@ struct bpf_verifier_env { int stack_size; /* number of states to be processed */ struct bpf_verifier_state cur_state; /* current verifier state */ struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ + const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */ + void *analyzer_priv; /* pointer to external analyzer's private data */ struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ u32 used_map_cnt; /* number of used maps */ u32 id_gen; /* used to generate unique reg IDs */ @@ -76,4 +84,7 @@ struct bpf_verifier_env { struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ }; +int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, + void *priv); + #endif /* _LINUX_BPF_VERIFIER_H */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index dca2b9b1d02e..ee86a77dc40b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -632,6 +632,10 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off, static int check_ctx_access(struct bpf_verifier_env *env, int off, int size, enum bpf_access_type t, enum bpf_reg_type *reg_type) { + /* for analyzer ctx accesses are already validated and converted */ + if (env->analyzer_ops) + return 0; + if (env->prog->aux->ops->is_valid_access && env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { /* remember the offset of last byte accessed in ctx */ @@ -2225,6 +2229,15 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) return 0; } +static int ext_analyzer_insn_hook(struct bpf_verifier_env *env, + int insn_idx, int prev_insn_idx) +{ + if (!env->analyzer_ops || !env->analyzer_ops->insn_hook) + return 0; + + return env->analyzer_ops->insn_hook(env, insn_idx, prev_insn_idx); +} + static int do_check(struct bpf_verifier_env *env) { struct bpf_verifier_state *state = &env->cur_state; @@ -2283,6 +2296,10 @@ static int do_check(struct bpf_verifier_env *env) print_bpf_insn(insn); } + err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx); + if (err) + return err; + if (class == BPF_ALU || class == BPF_ALU64) { err = check_alu_op(env, insn); if (err) @@ -2845,3 +2862,54 @@ err_free_env: kfree(env); return ret; } + +int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, + void *priv) +{ + struct bpf_verifier_env *env; + int ret; + + env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL); + if (!env) + return -ENOMEM; + + env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) * + prog->len); + ret = -ENOMEM; + if (!env->insn_aux_data) + goto err_free_env; + env->prog = prog; + env->analyzer_ops = ops; + env->analyzer_priv = priv; + + /* grab the mutex to protect few globals used by verifier */ + mutex_lock(&bpf_verifier_lock); + + log_level = 0; + + env->explored_states = kcalloc(env->prog->len, + sizeof(struct bpf_verifier_state_list *), + GFP_KERNEL); + ret = -ENOMEM; + if (!env->explored_states) + goto skip_full_check; + + ret = check_cfg(env); + if (ret < 0) + goto skip_full_check; + + env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); + + ret = do_check(env); + +skip_full_check: + while (pop_stack(env, NULL) >= 0); + free_states(env); + + mutex_unlock(&bpf_verifier_lock); + vfree(env->insn_aux_data); +err_free_env: + kfree(env); + return ret; +} +EXPORT_SYMBOL_GPL(bpf_analyzer); -- 2.20.1