[PATCH bpf-next v1 1/5] bpf: Add ARG_SCALAR and ARG_CONSTANT
STALE1666d
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: 2022-03-06 23:43:25
Also in:
bpf
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
In the next patch, we will introduce a new helper 'bpf_packet_pointer' that takes offset and len and returns a packet pointer. There we want to statically enforce offset is in range [0, 0xffff], and that len is a constant value, in range [1, 0xffff]. This also helps us avoid a pointless runtime check. To make these checks possible, we need to ensure we only get a scalar type. Although a lot of other argument types take scalars, their intent is different. Hence add general ARG_SCALAR and ARG_CONSTANT types, where the latter is also checked to be constant in addition to being scalar. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- include/linux/bpf.h | 2 ++ kernel/bpf/verifier.c | 13 +++++++++++++ 2 files changed, 15 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 88449fbbe063..7841d90b83df 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h@@ -391,6 +391,8 @@ enum bpf_arg_type { ARG_PTR_TO_STACK, /* pointer to stack */ ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */ ARG_PTR_TO_TIMER, /* pointer to bpf_timer */ + ARG_SCALAR, /* a scalar with any value(s) */ + ARG_CONSTANT, /* a scalar with constant value */ __BPF_ARG_TYPE_MAX, /* Extended arg_types. */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ec3a7b6c9515..0373d5bd240f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c@@ -5163,6 +5163,12 @@ static bool arg_type_is_int_ptr(enum bpf_arg_type type) type == ARG_PTR_TO_LONG; } +static bool arg_type_is_scalar(enum bpf_arg_type type) +{ + return type == ARG_SCALAR || + type == ARG_CONSTANT; +} + static int int_ptr_type_to_size(enum bpf_arg_type type) { if (type == ARG_PTR_TO_INT)
@@ -5302,6 +5308,8 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = { [ARG_PTR_TO_STACK] = &stack_ptr_types, [ARG_PTR_TO_CONST_STR] = &const_str_ptr_types, [ARG_PTR_TO_TIMER] = &timer_types, + [ARG_SCALAR] = &scalar_types, + [ARG_CONSTANT] = &scalar_types, }; static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
@@ -5635,6 +5643,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, verbose(env, "string is not zero-terminated\n"); return -EINVAL; } + } else if (arg_type_is_scalar(arg_type)) { + if (arg_type == ARG_CONSTANT && !tnum_is_const(reg->var_off)) { + verbose(env, "R%d is not a known constant\n", regno); + return -EACCES; + } } return err;
--
2.35.1