From: Florent Revest <revest@chromium.org>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
yhs@fb.com, kpsingh@kernel.org, jackmanb@chromium.org,
linux-kernel@vger.kernel.org,
Florent Revest <revest@chromium.org>
Subject: [PATCH bpf-next v3 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type
Date: Mon, 12 Apr 2021 17:37:50 +0200 [thread overview]
Message-ID: <20210412153754.235500-3-revest@chromium.org> (raw)
In-Reply-To: <20210412153754.235500-1-revest@chromium.org>
This type provides the guarantee that an argument is going to be a const
pointer to somewhere in a read-only map value. It also checks that this
pointer is followed by a zero character before the end of the map value.
Signed-off-by: Florent Revest <revest@chromium.org>
---
include/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ff8cd68c01b3..7d389eeee0b3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -309,6 +309,7 @@ enum bpf_arg_type {
ARG_PTR_TO_PERCPU_BTF_ID, /* pointer to in-kernel percpu type */
ARG_PTR_TO_FUNC, /* pointer to a bpf program function */
ARG_PTR_TO_STACK_OR_NULL, /* pointer to stack or NULL */
+ ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */
__BPF_ARG_TYPE_MAX,
};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 852541a435ef..5f46dd6f3383 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4787,6 +4787,7 @@ static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALU
static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_PERCPU_BTF_ID } };
static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } };
static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } };
+static const struct bpf_reg_types const_str_ptr_types = { .types = { PTR_TO_MAP_VALUE } };
static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
[ARG_PTR_TO_MAP_KEY] = &map_key_value_types,
@@ -4817,6 +4818,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
[ARG_PTR_TO_PERCPU_BTF_ID] = &percpu_btf_ptr_types,
[ARG_PTR_TO_FUNC] = &func_ptr_types,
[ARG_PTR_TO_STACK_OR_NULL] = &stack_ptr_types,
+ [ARG_PTR_TO_CONST_STR] = &const_str_ptr_types,
};
static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
@@ -5067,6 +5069,45 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
if (err)
return err;
err = check_ptr_alignment(env, reg, 0, size, true);
+ } else if (arg_type == ARG_PTR_TO_CONST_STR) {
+ struct bpf_map *map = reg->map_ptr;
+ int map_off;
+ u64 map_addr;
+ char *str_ptr;
+
+ if (reg->type != PTR_TO_MAP_VALUE || !map ||
+ !bpf_map_is_rdonly(map)) {
+ verbose(env, "R%d does not point to a readonly map'\n", regno);
+ return -EACCES;
+ }
+
+ if (!tnum_is_const(reg->var_off)) {
+ verbose(env, "R%d is not a constant address'\n", regno);
+ return -EACCES;
+ }
+
+ if (!map->ops->map_direct_value_addr) {
+ verbose(env, "no direct value access support for this map type\n");
+ return -EACCES;
+ }
+
+ err = check_map_access(env, regno, reg->off,
+ map->value_size - reg->off, false);
+ if (err)
+ return err;
+
+ map_off = reg->off + reg->var_off.value;
+ err = map->ops->map_direct_value_addr(map, &map_addr, map_off);
+ if (err) {
+ verbose(env, "direct value access on string failed\n");
+ return err;
+ }
+
+ str_ptr = (char *)(long)(map_addr);
+ if (!strnchr(str_ptr + map_off, map->value_size - map_off, 0)) {
+ verbose(env, "string is not zero-terminated\n");
+ return -EINVAL;
+ }
}
return err;
--
2.31.1.295.g9ea45b61b8-goog
next prev parent reply other threads:[~2021-04-12 15:38 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 15:37 [PATCH bpf-next v3 0/6] Add a snprintf eBPF helper Florent Revest
2021-04-12 15:37 ` [PATCH bpf-next v3 1/6] bpf: Factorize bpf_trace_printk and bpf_seq_printf Florent Revest
2021-04-13 23:01 ` Andrii Nakryiko
2021-04-14 9:56 ` Florent Revest
2021-04-14 10:56 ` Florent Revest
2021-04-12 15:37 ` Florent Revest [this message]
2021-04-13 23:03 ` [PATCH bpf-next v3 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Andrii Nakryiko
2021-04-12 15:37 ` [PATCH bpf-next v3 3/6] bpf: Add a bpf_snprintf helper Florent Revest
2021-04-12 19:11 ` kernel test robot
2021-04-12 20:32 ` kernel test robot
2021-04-14 13:32 ` Florent Revest
2021-04-12 20:40 ` kernel test robot
2021-04-13 23:16 ` Andrii Nakryiko
2021-04-14 9:46 ` Florent Revest
2021-04-14 22:57 ` Andrii Nakryiko
2021-04-15 9:34 ` Florent Revest
2021-04-14 18:02 ` Geert Uytterhoeven
2021-04-14 18:30 ` Florent Revest
2021-04-14 22:58 ` Andrii Nakryiko
2021-04-15 7:18 ` Geert Uytterhoeven
2021-04-12 15:37 ` [PATCH bpf-next v3 4/6] libbpf: Initialize the bpf_seq_printf parameters array field by field Florent Revest
2021-04-13 23:18 ` Andrii Nakryiko
2021-04-12 15:37 ` [PATCH bpf-next v3 5/6] libbpf: Introduce a BPF_SNPRINTF helper macro Florent Revest
2021-04-13 23:18 ` Andrii Nakryiko
2021-04-12 15:37 ` [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf Florent Revest
2021-04-13 23:21 ` Andrii Nakryiko
2021-04-14 9:21 ` Florent Revest
2021-04-14 22:16 ` Andrii Nakryiko
2021-04-15 9:38 ` Florent Revest
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