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Merge branch 'bpf-unify-special-map-field-validation-in-verifier'

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Mykyta Yatsenko says:

====================
The BPF verifier validates pointers to special map fields (timers,
workqueues, task_work) through separate functions that share nearly
identical logic. This creates code duplication because of the
inconsistent data structure layout in struct bpf_call_arg_meta struct
bpf_kfunc_call_arg_meta.

This series contains 2 commits:

1. Introduces struct bpf_map_desc to provide a unified representation
for map pointer and uid tracking. Previously, bpf_call_arg_meta used
separate map_ptr and map_uid fields while bpf_kfunc_call_arg_metaused an
anonymous inline struct. This inconsistency made it harder to share
validation code between the two paths.

2. Consolidates the validation logic for BPF_TIMER, BPF_WORKQUEUE, and
BPF_TASK_WORK field types into a single check_map_field_pointer()
function. This eliminates process_wq_func() and process_task_work_func()
entirely, and simplifies process_timer_func() to just the PREEMPT_RT
check before calling the unified validation. The result is fewer
lines of code with clearer structure for future maintenance.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>

Changes in v2:
- Added Signed-off-by to the top commit.
- Link to v1: https://lore.kernel.org/r/20260129-verif_special_fields-v1-0-d310b7f146c8@meta.com
====================

Link: https://patch.msgid.link/20260130-verif_special_fields-v2-0-2c59e637da7d@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2026-01-30 21:13:48 -08:00
commit cda0cbfdee
1 changed files with 48 additions and 95 deletions
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143
kernel/bpf/verifier.c
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@ -272,8 +272,13 @@ static bool bpf_pseudo_kfunc_call(const struct bpf_insn *insn)
insn->src_reg == BPF_PSEUDO_KFUNC_CALL;
}
struct bpf_map_desc {
struct bpf_map *ptr;
int uid;
};
struct bpf_call_arg_meta {
struct bpf_map *map_ptr;
struct bpf_map_desc map;
bool raw_mode;
bool pkt_access;
u8 release_regno;
@ -283,7 +288,6 @@ struct bpf_call_arg_meta {
u64 msize_max_value;
int ref_obj_id;
int dynptr_id;
int map_uid;
int func_id;
struct btf *btf;
u32 btf_id;
@ -351,10 +355,7 @@ struct bpf_kfunc_call_arg_meta {
u8 spi;
u8 frameno;
} iter;
struct {
struct bpf_map *ptr;
int uid;
} map;
struct bpf_map_desc map;
u64 mem_size;
};
@ -8609,7 +8610,8 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno, int flags)
/* Check if @regno is a pointer to a specific field in a map value */
static int check_map_field_pointer(struct bpf_verifier_env *env, u32 regno,
enum btf_field_type field_type)
enum btf_field_type field_type,
struct bpf_map_desc *map_desc)
{
struct bpf_reg_state *reg = reg_state(env, regno);
bool is_const = tnum_is_const(reg->var_off);
@ -8652,72 +8654,23 @@ static int check_map_field_pointer(struct bpf_verifier_env *env, u32 regno,
val + reg->off, struct_name, field_off);
return -EINVAL;
}
if (map_desc->ptr) {
verifier_bug(env, "Two map pointers in a %s helper", struct_name);
return -EFAULT;
}
map_desc->uid = reg->map_uid;
map_desc->ptr = map;
return 0;
}
static int process_timer_func(struct bpf_verifier_env *env, int regno,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_map *map = reg->map_ptr;
int err;
err = check_map_field_pointer(env, regno, BPF_TIMER);
if (err)
return err;
if (meta->map_ptr) {
verifier_bug(env, "Two map pointers in a timer helper");
return -EFAULT;
}
if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
verbose(env, "bpf_timer cannot be used for PREEMPT_RT.\n");
return -EOPNOTSUPP;
}
meta->map_uid = reg->map_uid;
meta->map_ptr = map;
return 0;
}
static int process_wq_func(struct bpf_verifier_env *env, int regno,
struct bpf_kfunc_call_arg_meta *meta)
{
struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_map *map = reg->map_ptr;
int err;
err = check_map_field_pointer(env, regno, BPF_WORKQUEUE);
if (err)
return err;
if (meta->map.ptr) {
verifier_bug(env, "Two map pointers in a bpf_wq helper");
return -EFAULT;
}
meta->map.uid = reg->map_uid;
meta->map.ptr = map;
return 0;
}
static int process_task_work_func(struct bpf_verifier_env *env, int regno,
struct bpf_kfunc_call_arg_meta *meta)
{
struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_map *map = reg->map_ptr;
int err;
err = check_map_field_pointer(env, regno, BPF_TASK_WORK);
if (err)
return err;
if (meta->map.ptr) {
verifier_bug(env, "Two map pointers in a bpf_task_work helper");
return -EFAULT;
}
meta->map.uid = reg->map_uid;
meta->map.ptr = map;
return 0;
return check_map_field_pointer(env, regno, BPF_TIMER, &meta->map);
}
static int process_kptr_func(struct bpf_verifier_env *env, int regno,
@ -8739,7 +8692,7 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
return -EINVAL;
}
rec = map_ptr->record;
meta->map_ptr = map_ptr;
meta->map.ptr = map_ptr;
}
if (!tnum_is_const(reg->var_off)) {
@ -9246,13 +9199,13 @@ static int resolve_map_arg_type(struct bpf_verifier_env *env,
const struct bpf_call_arg_meta *meta,
enum bpf_arg_type *arg_type)
{
if (!meta->map_ptr) {
if (!meta->map.ptr) {
/* kernel subsystem misconfigured verifier */
verifier_bug(env, "invalid map_ptr to access map->type");
return -EFAULT;
}
switch (meta->map_ptr->map_type) {
switch (meta->map.ptr->map_type) {
case BPF_MAP_TYPE_SOCKMAP:
case BPF_MAP_TYPE_SOCKHASH:
if (*arg_type == ARG_PTR_TO_MAP_VALUE) {
@ -9906,7 +9859,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
switch (base_type(arg_type)) {
case ARG_CONST_MAP_PTR:
/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
if (meta->map_ptr) {
if (meta->map.ptr) {
/* Use map_uid (which is unique id of inner map) to reject:
* inner_map1 = bpf_map_lookup_elem(outer_map, key1)
* inner_map2 = bpf_map_lookup_elem(outer_map, key2)
@ -9919,23 +9872,23 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
*
* Comparing map_ptr is enough to distinguish normal and outer maps.
*/
if (meta->map_ptr != reg->map_ptr ||
meta->map_uid != reg->map_uid) {
if (meta->map.ptr != reg->map_ptr ||
meta->map.uid != reg->map_uid) {
verbose(env,
"timer pointer in R1 map_uid=%d doesn't match map pointer in R2 map_uid=%d\n",
meta->map_uid, reg->map_uid);
meta->map.uid, reg->map_uid);
return -EINVAL;
}
}
meta->map_ptr = reg->map_ptr;
meta->map_uid = reg->map_uid;
meta->map.ptr = reg->map_ptr;
meta->map.uid = reg->map_uid;
break;
case ARG_PTR_TO_MAP_KEY:
/* bpf_map_xxx(..., map_ptr, ..., key) call:
* check that [key, key + map->key_size) are within
* stack limits and initialized
*/
if (!meta->map_ptr) {
if (!meta->map.ptr) {
/* in function declaration map_ptr must come before
* map_key, so that it's verified and known before
* we have to check map_key here. Otherwise it means
@ -9944,11 +9897,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
verifier_bug(env, "invalid map_ptr to access map->key");
return -EFAULT;
}
key_size = meta->map_ptr->key_size;
key_size = meta->map.ptr->key_size;
err = check_helper_mem_access(env, regno, key_size, BPF_READ, false, NULL);
if (err)
return err;
if (can_elide_value_nullness(meta->map_ptr->map_type)) {
if (can_elide_value_nullness(meta->map.ptr->map_type)) {
err = get_constant_map_key(env, reg, key_size, &meta->const_map_key);
if (err < 0) {
meta->const_map_key = -1;
@ -9966,13 +9919,13 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
/* bpf_map_xxx(..., map_ptr, ..., value) call:
* check [value, value + map->value_size) validity
*/
if (!meta->map_ptr) {
if (!meta->map.ptr) {
/* kernel subsystem misconfigured verifier */
verifier_bug(env, "invalid map_ptr to access map->value");
return -EFAULT;
}
meta->raw_mode = arg_type & MEM_UNINIT;
err = check_helper_mem_access(env, regno, meta->map_ptr->value_size,
err = check_helper_mem_access(env, regno, meta->map.ptr->value_size,
arg_type & MEM_WRITE ? BPF_WRITE : BPF_READ,
false, meta);
break;
@ -11310,7 +11263,7 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
int func_id, int insn_idx)
{
struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
struct bpf_map *map = meta->map_ptr;
struct bpf_map *map = meta->map.ptr;
if (func_id != BPF_FUNC_tail_call &&
func_id != BPF_FUNC_map_lookup_elem &&
@ -11343,11 +11296,11 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
}
if (!aux->map_ptr_state.map_ptr)
bpf_map_ptr_store(aux, meta->map_ptr,
!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);
bpf_map_ptr_store(aux, meta->map.ptr,
!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;
}
@ -11357,7 +11310,7 @@ record_func_key(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
{
struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
struct bpf_reg_state *reg;
struct bpf_map *map = meta->map_ptr;
struct bpf_map *map = meta->map.ptr;
u64 val, max;
int err;
@ -11913,22 +11866,22 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
* can check 'value_size' boundary of memory access
* to map element returned from bpf_map_lookup_elem()
*/
if (meta.map_ptr == NULL) {
if (meta.map.ptr == NULL) {
verifier_bug(env, "unexpected null map_ptr");
return -EFAULT;
}
if (func_id == BPF_FUNC_map_lookup_elem &&
can_elide_value_nullness(meta.map_ptr->map_type) &&
can_elide_value_nullness(meta.map.ptr->map_type) &&
meta.const_map_key >= 0 &&
meta.const_map_key < meta.map_ptr->max_entries)
meta.const_map_key < meta.map.ptr->max_entries)
ret_flag &= ~PTR_MAYBE_NULL;
regs[BPF_REG_0].map_ptr = meta.map_ptr;
regs[BPF_REG_0].map_uid = meta.map_uid;
regs[BPF_REG_0].map_ptr = meta.map.ptr;
regs[BPF_REG_0].map_uid = meta.map.uid;
regs[BPF_REG_0].type = PTR_TO_MAP_VALUE | ret_flag;
if (!type_may_be_null(ret_flag) &&
btf_record_has_field(meta.map_ptr->record, BPF_SPIN_LOCK | BPF_RES_SPIN_LOCK)) {
btf_record_has_field(meta.map.ptr->record, BPF_SPIN_LOCK | BPF_RES_SPIN_LOCK)) {
regs[BPF_REG_0].id = ++env->id_gen;
}
break;
@ -12031,7 +11984,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
if (type_may_be_null(regs[BPF_REG_0].type))
regs[BPF_REG_0].id = ++env->id_gen;
if (helper_multiple_ref_obj_use(func_id, meta.map_ptr)) {
if (helper_multiple_ref_obj_use(func_id, meta.map.ptr)) {
verifier_bug(env, "func %s#%d sets ref_obj_id more than once",
func_id_name(func_id), func_id);
return -EFAULT;
@ -12043,7 +11996,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
if (is_ptr_cast_function(func_id) || is_dynptr_ref_function(func_id)) {
/* For release_reference() */
regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id;
} else if (is_acquire_function(func_id, meta.map_ptr)) {
} else if (is_acquire_function(func_id, meta.map.ptr)) {
int id = acquire_reference(env, insn_idx);
if (id < 0)
@ -12058,7 +12011,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
if (err)
return err;
err = check_map_func_compatibility(env, meta.map_ptr, func_id);
err = check_map_func_compatibility(env, meta.map.ptr, func_id);
if (err)
return err;
@ -13753,7 +13706,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
verbose(env, "arg#%d doesn't point to a map value\n", i);
return -EINVAL;
}
ret = process_wq_func(env, regno, meta);
ret = check_map_field_pointer(env, regno, BPF_WORKQUEUE, &meta->map);
if (ret < 0)
return ret;
break;
@ -13762,7 +13715,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
verbose(env, "arg#%d doesn't point to a map value\n", i);
return -EINVAL;
}
ret = process_task_work_func(env, regno, meta);
ret = check_map_field_pointer(env, regno, BPF_TASK_WORK, &meta->map);
if (ret < 0)
return ret;
break;