Commit f79e7ea5 authored by Lorenz Bauer's avatar Lorenz Bauer Committed by Alexei Starovoitov
Browse files

bpf: Use a table to drive helper arg type checks 



The mapping between bpf_arg_type and bpf_reg_type is encoded in a big
hairy if statement that is hard to follow. The debug output also leaves
to be desired: if a reg_type doesn't match we only print one of the
options, instead printing all the valid ones.

Convert the if statement into a table which is then used to drive type
checking. If none of the reg_types match we print all options, e.g.:

    R2 type=rdonly_buf expected=fp, pkt, pkt_meta, map_value

Signed-off-by: default avatarLorenz Bauer <lmb@cloudflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-12-lmb@cloudflare.com
parent fd1b0d60

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -292,6 +292,7 @@ enum bpf_arg_type { 
	ARG_PTR_TO_ALLOC_MEM,	/* pointer to dynamically allocated memory */

	ARG_PTR_TO_ALLOC_MEM_OR_NULL,	/* pointer to dynamically allocated memory or NULL */

	ARG_CONST_ALLOC_SIZE_OR_ZERO,	/* number of allocated bytes requested */

	__BPF_ARG_TYPE_MAX,

};



/* type of values returned from helper functions */

kernel/bpf/verifier.c

+109 −74
Original line number Diff line number Diff line
@@ -3903,12 +3903,6 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type) 
	       type == ARG_CONST_SIZE_OR_ZERO;

}



static bool arg_type_is_alloc_mem_ptr(enum bpf_arg_type type)

{

	return type == ARG_PTR_TO_ALLOC_MEM ||

	       type == ARG_PTR_TO_ALLOC_MEM_OR_NULL;

}



static bool arg_type_is_alloc_size(enum bpf_arg_type type)

{

	return type == ARG_CONST_ALLOC_SIZE_OR_ZERO;
@@ -3957,14 +3951,115 @@ static int resolve_map_arg_type(struct bpf_verifier_env *env, 
	return 0;

}



struct bpf_reg_types {

	const enum bpf_reg_type types[10];

};



static const struct bpf_reg_types map_key_value_types = {

	.types = {

		PTR_TO_STACK,

		PTR_TO_PACKET,

		PTR_TO_PACKET_META,

		PTR_TO_MAP_VALUE,

	},

};



static const struct bpf_reg_types sock_types = {

	.types = {

		PTR_TO_SOCK_COMMON,

		PTR_TO_SOCKET,

		PTR_TO_TCP_SOCK,

		PTR_TO_XDP_SOCK,

	},

};



static const struct bpf_reg_types mem_types = {

	.types = {

		PTR_TO_STACK,

		PTR_TO_PACKET,

		PTR_TO_PACKET_META,

		PTR_TO_MAP_VALUE,

		PTR_TO_MEM,

		PTR_TO_RDONLY_BUF,

		PTR_TO_RDWR_BUF,

	},

};



static const struct bpf_reg_types int_ptr_types = {

	.types = {

		PTR_TO_STACK,

		PTR_TO_PACKET,

		PTR_TO_PACKET_META,

		PTR_TO_MAP_VALUE,

	},

};



static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };

static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };

static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };

static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };

static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };

static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };

static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };



static const struct bpf_reg_types *compatible_reg_types[] = {

	[ARG_PTR_TO_MAP_KEY]		= &map_key_value_types,

	[ARG_PTR_TO_MAP_VALUE]		= &map_key_value_types,

	[ARG_PTR_TO_UNINIT_MAP_VALUE]	= &map_key_value_types,

	[ARG_PTR_TO_MAP_VALUE_OR_NULL]	= &map_key_value_types,

	[ARG_CONST_SIZE]		= &scalar_types,

	[ARG_CONST_SIZE_OR_ZERO]	= &scalar_types,

	[ARG_CONST_ALLOC_SIZE_OR_ZERO]	= &scalar_types,

	[ARG_CONST_MAP_PTR]		= &const_map_ptr_types,

	[ARG_PTR_TO_CTX]		= &context_types,

	[ARG_PTR_TO_CTX_OR_NULL]	= &context_types,

	[ARG_PTR_TO_SOCK_COMMON]	= &sock_types,

	[ARG_PTR_TO_SOCKET]		= &fullsock_types,

	[ARG_PTR_TO_SOCKET_OR_NULL]	= &fullsock_types,

	[ARG_PTR_TO_BTF_ID]		= &btf_ptr_types,

	[ARG_PTR_TO_SPIN_LOCK]		= &spin_lock_types,

	[ARG_PTR_TO_MEM]		= &mem_types,

	[ARG_PTR_TO_MEM_OR_NULL]	= &mem_types,

	[ARG_PTR_TO_UNINIT_MEM]		= &mem_types,

	[ARG_PTR_TO_ALLOC_MEM]		= &alloc_mem_types,

	[ARG_PTR_TO_ALLOC_MEM_OR_NULL]	= &alloc_mem_types,

	[ARG_PTR_TO_INT]		= &int_ptr_types,

	[ARG_PTR_TO_LONG]		= &int_ptr_types,

	[__BPF_ARG_TYPE_MAX]		= NULL,

};



static int check_reg_type(struct bpf_verifier_env *env, u32 regno,

			  const struct bpf_reg_types *compatible)

{

	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];

	enum bpf_reg_type expected, type = reg->type;

	int i, j;



	for (i = 0; i < ARRAY_SIZE(compatible->types); i++) {

		expected = compatible->types[i];

		if (expected == NOT_INIT)

			break;



		if (type == expected)

			return 0;

	}



	verbose(env, "R%d type=%s expected=", regno, reg_type_str[type]);

	for (j = 0; j + 1 < i; j++)

		verbose(env, "%s, ", reg_type_str[compatible->types[j]]);

	verbose(env, "%s\n", reg_type_str[compatible->types[j]]);

	return -EACCES;

}



static int check_func_arg(struct bpf_verifier_env *env, u32 arg,

			  struct bpf_call_arg_meta *meta,

			  const struct bpf_func_proto *fn)

{

	u32 regno = BPF_REG_1 + arg;

	struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];

	enum bpf_reg_type expected_type, type = reg->type;

	enum bpf_arg_type arg_type = fn->arg_type[arg];

	const struct bpf_reg_types *compatible;

	enum bpf_reg_type type = reg->type;

	int err = 0;



	if (arg_type == ARG_DONTCARE)
@@ -4003,72 +4098,16 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, 
		 */

		goto skip_type_check;



	if (arg_type == ARG_PTR_TO_MAP_KEY ||

	    arg_type == ARG_PTR_TO_MAP_VALUE ||

	    arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE ||

	    arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL) {

		expected_type = PTR_TO_STACK;

		if (!type_is_pkt_pointer(type) &&

		    type != PTR_TO_MAP_VALUE &&

		    type != expected_type)

			goto err_type;

	} else if (arg_type == ARG_CONST_SIZE ||

		   arg_type == ARG_CONST_SIZE_OR_ZERO ||

		   arg_type == ARG_CONST_ALLOC_SIZE_OR_ZERO) {

		expected_type = SCALAR_VALUE;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type == ARG_CONST_MAP_PTR) {

		expected_type = CONST_PTR_TO_MAP;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type == ARG_PTR_TO_CTX ||

		   arg_type == ARG_PTR_TO_CTX_OR_NULL) {

		expected_type = PTR_TO_CTX;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type == ARG_PTR_TO_SOCK_COMMON) {

		expected_type = PTR_TO_SOCK_COMMON;

		/* Any sk pointer can be ARG_PTR_TO_SOCK_COMMON */

		if (!type_is_sk_pointer(type))

			goto err_type;

	} else if (arg_type == ARG_PTR_TO_SOCKET ||

		   arg_type == ARG_PTR_TO_SOCKET_OR_NULL) {

		expected_type = PTR_TO_SOCKET;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type == ARG_PTR_TO_BTF_ID) {

		expected_type = PTR_TO_BTF_ID;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {

		expected_type = PTR_TO_MAP_VALUE;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type_is_mem_ptr(arg_type)) {

		expected_type = PTR_TO_STACK;

		if (!type_is_pkt_pointer(type) &&

		    type != PTR_TO_MAP_VALUE &&

		    type != PTR_TO_MEM &&

		    type != PTR_TO_RDONLY_BUF &&

		    type != PTR_TO_RDWR_BUF &&

		    type != expected_type)

			goto err_type;

	} else if (arg_type_is_alloc_mem_ptr(arg_type)) {

		expected_type = PTR_TO_MEM;

		if (type != expected_type)

			goto err_type;

	} else if (arg_type_is_int_ptr(arg_type)) {

		expected_type = PTR_TO_STACK;

		if (!type_is_pkt_pointer(type) &&

		    type != PTR_TO_MAP_VALUE &&

		    type != expected_type)

			goto err_type;

	} else {

		verbose(env, "unsupported arg_type %d\n", arg_type);

	compatible = compatible_reg_types[arg_type];

	if (!compatible) {

		verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);

		return -EFAULT;

	}



	err = check_reg_type(env, regno, compatible);

	if (err)

		return err;



	if (type == PTR_TO_BTF_ID) {

		const u32 *btf_id = fn->arg_btf_id[arg];
@@ -4221,10 +4260,6 @@ skip_type_check: 
	}



	return err;

err_type:

	verbose(env, "R%d type=%s expected=%s\n", regno,

		reg_type_str[type], reg_type_str[expected_type]);

	return -EACCES;

}



static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)

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