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bpf: store both map ptr and state in bpf_insn_aux_data

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Currently, bpf_insn_aux_data->map_ptr_state is used to store either
map_ptr or its poison state (i.e., BPF_MAP_PTR_POISON). Thus
BPF_MAP_PTR_POISON must be checked before reading map_ptr. In certain
cases, we may need valid map_ptr even in case of poison state.
This will be explained in next patch with bpf_for_each_map_elem()
helper.

This patch changes map_ptr_state into a new struct including both map
pointer and its state (poison/unpriv). It's in the same union with
struct bpf_loop_inline_state, so there is no extra memory overhead.
Besides, macros BPF_MAP_PTR_UNPRIV/BPF_MAP_PTR_POISON/BPF_MAP_PTR are no
longer needed.

This patch does not change any existing functionality.

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240405025536.18113-2-lulie@linux.alibaba.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Philo Lu 2024-04-05 10:55:34 +08:00 • committed by Alexei Starovoitov
parent 58babe2718
commit 0a525621b7
2 changed files with 24 additions and 21 deletions
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9
include/linux/bpf_verifier.h
View file

@ -502,6 +502,13 @@ struct bpf_loop_inline_state {
u32 callback_subprogno; /* valid when fit_for_inline is true */
};
/* pointer and state for maps */
struct bpf_map_ptr_state {
struct bpf_map *map_ptr;
bool poison;
bool unpriv;
};
/* Possible states for alu_state member. */
#define BPF_ALU_SANITIZE_SRC (1U << 0)
#define BPF_ALU_SANITIZE_DST (1U << 1)
@ -514,7 +521,7 @@ struct bpf_loop_inline_state {
struct bpf_insn_aux_data {
union {
enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
unsigned long map_ptr_state; /* pointer/poison value for maps */
struct bpf_map_ptr_state map_ptr_state;
s32 call_imm; /* saved imm field of call insn */
u32 alu_limit; /* limit for add/sub register with pointer */
struct {

36
kernel/bpf/verifier.c
View file

@ -190,11 +190,6 @@ struct bpf_verifier_stack_elem {
#define BPF_MAP_KEY_POISON (1ULL << 63)
#define BPF_MAP_KEY_SEEN (1ULL << 62)
#define BPF_MAP_PTR_UNPRIV 1UL
#define BPF_MAP_PTR_POISON ((void *)((0xeB9FUL << 1) + \
POISON_POINTER_DELTA))
#define BPF_MAP_PTR(X) ((struct bpf_map *)((X) & ~BPF_MAP_PTR_UNPRIV))
#define BPF_GLOBAL_PERCPU_MA_MAX_SIZE 512
static int acquire_reference_state(struct bpf_verifier_env *env, int insn_idx);
@ -209,21 +204,22 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg);
static bool bpf_map_ptr_poisoned(const struct bpf_insn_aux_data *aux)
{
return BPF_MAP_PTR(aux->map_ptr_state) == BPF_MAP_PTR_POISON;
return aux->map_ptr_state.poison;
}
static bool bpf_map_ptr_unpriv(const struct bpf_insn_aux_data *aux)
{
return aux->map_ptr_state & BPF_MAP_PTR_UNPRIV;
return aux->map_ptr_state.unpriv;
}
static void bpf_map_ptr_store(struct bpf_insn_aux_data *aux,
const struct bpf_map *map, bool unpriv)
struct bpf_map *map,
bool unpriv, bool poison)
{
BUILD_BUG_ON((unsigned long)BPF_MAP_PTR_POISON & BPF_MAP_PTR_UNPRIV);
unpriv |= bpf_map_ptr_unpriv(aux);
aux->map_ptr_state = (unsigned long)map |
(unpriv ? BPF_MAP_PTR_UNPRIV : 0UL);
aux->map_ptr_state.unpriv = unpriv;
aux->map_ptr_state.poison = poison;
aux->map_ptr_state.map_ptr = map;
}
static bool bpf_map_key_poisoned(const struct bpf_insn_aux_data *aux)
@ -9660,7 +9656,7 @@ static int set_map_elem_callback_state(struct bpf_verifier_env *env,
return -EINVAL;
}
map = BPF_MAP_PTR(insn_aux->map_ptr_state);
map = insn_aux->map_ptr_state.map_ptr;
if (!map->ops->map_set_for_each_callback_args ||
!map->ops->map_for_each_callback) {
verbose(env, "callback function not allowed for map\n");
@ -10019,12 +10015,12 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
return -EACCES;
}
if (!BPF_MAP_PTR(aux->map_ptr_state))
if (!aux->map_ptr_state.map_ptr)
bpf_map_ptr_store(aux, meta->map_ptr,
!meta->map_ptr->bypass_spec_v1);
else if (BPF_MAP_PTR(aux->map_ptr_state) != meta->map_ptr)
bpf_map_ptr_store(aux, BPF_MAP_PTR_POISON,
!meta->map_ptr->bypass_spec_v1);
!meta->map_ptr->bypass_spec_v1, false);
else if (aux->map_ptr_state.map_ptr != meta->map_ptr)
bpf_map_ptr_store(aux, meta->map_ptr,
!meta->map_ptr->bypass_spec_v1, true);
return 0;
}
@ -19840,7 +19836,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
!bpf_map_ptr_unpriv(aux)) {
struct bpf_jit_poke_descriptor desc = {
.reason = BPF_POKE_REASON_TAIL_CALL,
.tail_call.map = BPF_MAP_PTR(aux->map_ptr_state),
.tail_call.map = aux->map_ptr_state.map_ptr,
.tail_call.key = bpf_map_key_immediate(aux),
.insn_idx = i + delta,
};
@ -19869,7 +19865,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
return -EINVAL;
}
map_ptr = BPF_MAP_PTR(aux->map_ptr_state);
map_ptr = aux->map_ptr_state.map_ptr;
insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3,
map_ptr->max_entries, 2);
insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3,
@ -19977,7 +19973,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
if (bpf_map_ptr_poisoned(aux))
goto patch_call_imm;
map_ptr = BPF_MAP_PTR(aux->map_ptr_state);
map_ptr = aux->map_ptr_state.map_ptr;
ops = map_ptr->ops;
if (insn->imm == BPF_FUNC_map_lookup_elem &&
ops->map_gen_lookup) {