Commit cda0cbfd authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

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



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: default avatarMykyta 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: default avatarAlexei Starovoitov <ast@kernel.org>
parents c7fbf8d9 f4e72ad7

kernel/bpf/verifier.c

+48 −95
Original line number Diff line number Diff line
@@ -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;