Commit 8c1b6e69 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann

bpf: Compare BTF types of functions arguments with actual types

Make the verifier check that BTF types of function arguments match actual types
passed into top-level BPF program and into BPF-to-BPF calls. If types match
such BPF programs and sub-programs will have full support of BPF trampoline. If
types mismatch the trampoline has to be conservative. It has to save/restore
five program arguments and assume 64-bit scalars.
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-17-ast@kernel.org
parent 91cc1a99
......@@ -480,6 +480,10 @@ static inline int bpf_trampoline_unlink_prog(struct bpf_prog *prog)
static inline void bpf_trampoline_put(struct bpf_trampoline *tr) {}
#endif
struct bpf_func_info_aux {
bool unreliable;
};
struct bpf_prog_aux {
atomic_t refcnt;
u32 used_map_cnt;
......@@ -494,6 +498,7 @@ struct bpf_prog_aux {
bool verifier_zext; /* Zero extensions has been inserted by verifier. */
bool offload_requested;
bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */
bool func_proto_unreliable;
enum bpf_tramp_prog_type trampoline_prog_type;
struct bpf_trampoline *trampoline;
struct hlist_node tramp_hlist;
......@@ -518,6 +523,7 @@ struct bpf_prog_aux {
struct bpf_prog_offload *offload;
struct btf *btf;
struct bpf_func_info *func_info;
struct bpf_func_info_aux *func_info_aux;
/* bpf_line_info loaded from userspace. linfo->insn_off
* has the xlated insn offset.
* Both the main and sub prog share the same linfo.
......@@ -890,6 +896,8 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
const char *func_name,
struct btf_func_model *m);
int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog);
#else /* !CONFIG_BPF_SYSCALL */
static inline struct bpf_prog *bpf_prog_get(u32 ufd)
{
......
......@@ -343,6 +343,7 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
#define BPF_MAX_SUBPROGS 256
struct bpf_subprog_info {
/* 'start' has to be the first field otherwise find_subprog() won't work */
u32 start; /* insn idx of function entry point */
u32 linfo_idx; /* The idx to the main_prog->aux->linfo */
u16 stack_depth; /* max. stack depth used by this function */
......
......@@ -3985,6 +3985,88 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
return 0;
}
int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog)
{
struct bpf_verifier_state *st = env->cur_state;
struct bpf_func_state *func = st->frame[st->curframe];
struct bpf_reg_state *reg = func->regs;
struct bpf_verifier_log *log = &env->log;
struct bpf_prog *prog = env->prog;
struct btf *btf = prog->aux->btf;
const struct btf_param *args;
const struct btf_type *t;
u32 i, nargs, btf_id;
const char *tname;
if (!prog->aux->func_info)
return 0;
btf_id = prog->aux->func_info[subprog].type_id;
if (!btf_id)
return 0;
if (prog->aux->func_info_aux[subprog].unreliable)
return 0;
t = btf_type_by_id(btf, btf_id);
if (!t || !btf_type_is_func(t)) {
bpf_log(log, "BTF of subprog %d doesn't point to KIND_FUNC\n",
subprog);
return -EINVAL;
}
tname = btf_name_by_offset(btf, t->name_off);
t = btf_type_by_id(btf, t->type);
if (!t || !btf_type_is_func_proto(t)) {
bpf_log(log, "Invalid type of func %s\n", tname);
return -EINVAL;
}
args = (const struct btf_param *)(t + 1);
nargs = btf_type_vlen(t);
if (nargs > 5) {
bpf_log(log, "Function %s has %d > 5 args\n", tname, nargs);
goto out;
}
/* check that BTF function arguments match actual types that the
* verifier sees.
*/
for (i = 0; i < nargs; i++) {
t = btf_type_by_id(btf, args[i].type);
while (btf_type_is_modifier(t))
t = btf_type_by_id(btf, t->type);
if (btf_type_is_int(t) || btf_type_is_enum(t)) {
if (reg[i + 1].type == SCALAR_VALUE)
continue;
bpf_log(log, "R%d is not a scalar\n", i + 1);
goto out;
}
if (btf_type_is_ptr(t)) {
if (reg[i + 1].type == SCALAR_VALUE) {
bpf_log(log, "R%d is not a pointer\n", i + 1);
goto out;
}
/* If program is passing PTR_TO_CTX into subprogram
* check that BTF type matches.
*/
if (reg[i + 1].type == PTR_TO_CTX &&
!btf_get_prog_ctx_type(log, btf, t, prog->type))
goto out;
/* All other pointers are ok */
continue;
}
bpf_log(log, "Unrecognized argument type %s\n",
btf_kind_str[BTF_INFO_KIND(t->info)]);
goto out;
}
return 0;
out:
/* LLVM optimizations can remove arguments from static functions. */
bpf_log(log,
"Type info disagrees with actual arguments due to compiler optimizations\n");
prog->aux->func_info_aux[subprog].unreliable = true;
return 0;
}
void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m)
{
......
......@@ -1328,6 +1328,7 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu)
struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
kvfree(aux->func_info);
kfree(aux->func_info_aux);
free_used_maps(aux);
bpf_prog_uncharge_memlock(aux->prog);
security_bpf_prog_free(aux);
......
......@@ -3970,6 +3970,9 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
/* only increment it after check_reg_arg() finished */
state->curframe++;
if (btf_check_func_arg_match(env, subprog))
return -EINVAL;
/* and go analyze first insn of the callee */
*insn_idx = target_insn;
......@@ -6564,6 +6567,7 @@ static int check_btf_func(struct bpf_verifier_env *env,
u32 i, nfuncs, urec_size, min_size;
u32 krec_size = sizeof(struct bpf_func_info);
struct bpf_func_info *krecord;
struct bpf_func_info_aux *info_aux = NULL;
const struct btf_type *type;
struct bpf_prog *prog;
const struct btf *btf;
......@@ -6597,6 +6601,9 @@ static int check_btf_func(struct bpf_verifier_env *env,
krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL | __GFP_NOWARN);
if (!krecord)
return -ENOMEM;
info_aux = kcalloc(nfuncs, sizeof(*info_aux), GFP_KERNEL | __GFP_NOWARN);
if (!info_aux)
goto err_free;
for (i = 0; i < nfuncs; i++) {
ret = bpf_check_uarg_tail_zero(urecord, krec_size, urec_size);
......@@ -6648,29 +6655,31 @@ static int check_btf_func(struct bpf_verifier_env *env,
ret = -EINVAL;
goto err_free;
}
prev_offset = krecord[i].insn_off;
urecord += urec_size;
}
prog->aux->func_info = krecord;
prog->aux->func_info_cnt = nfuncs;
prog->aux->func_info_aux = info_aux;
return 0;
err_free:
kvfree(krecord);
kfree(info_aux);
return ret;
}
static void adjust_btf_func(struct bpf_verifier_env *env)
{
struct bpf_prog_aux *aux = env->prog->aux;
int i;
if (!env->prog->aux->func_info)
if (!aux->func_info)
return;
for (i = 0; i < env->subprog_cnt; i++)
env->prog->aux->func_info[i].insn_off = env->subprog_info[i].start;
aux->func_info[i].insn_off = env->subprog_info[i].start;
}
#define MIN_BPF_LINEINFO_SIZE (offsetof(struct bpf_line_info, line_col) + \
......@@ -7651,6 +7660,9 @@ static int do_check(struct bpf_verifier_env *env)
0 /* frameno */,
0 /* subprogno, zero == main subprog */);
if (btf_check_func_arg_match(env, 0))
return -EINVAL;
for (;;) {
struct bpf_insn *insn;
u8 class;
......
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