From: Song Liu <song@kernel.org>
To: bpf@vger.kernel.org, fsverity@lists.linux.dev
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@kernel.org, kernel-team@meta.com, ebiggers@kernel.org,
tytso@mit.edu, roberto.sassu@huaweicloud.com, kpsingh@kernel.org,
vadfed@meta.com, Song Liu <song@kernel.org>
Subject: [PATCH v10 bpf-next 2/9] bpf: Factor out helper check_reg_const_str()
Date: Fri, 3 Nov 2023 14:45:28 -0700 [thread overview]
Message-ID: <20231103214535.2674059-3-song@kernel.org> (raw)
In-Reply-To: <20231103214535.2674059-1-song@kernel.org>
ARG_PTR_TO_CONST_STR is used to specify constant string args for BPF
helpers. The logic that verifies a reg is ARG_PTR_TO_CONST_STR is
implemented in check_func_arg().
As we introduce kfuncs with constant string args, it is necessary to
do the same check for kfuncs (in check_kfunc_args). Factor out the logic
for ARG_PTR_TO_CONST_STR to a new check_reg_const_str() so that it can be
reused.
check_func_arg() ensures check_reg_const_str() is only called with reg of
type PTR_TO_MAP_VALUE. Add a redundent type check in check_reg_const_str()
to avoid misuse in the future. Other than this redundent check, there is
no change in behavior.
Signed-off-by: Song Liu <song@kernel.org>
---
kernel/bpf/verifier.c | 85 +++++++++++++++++++++++++------------------
1 file changed, 49 insertions(+), 36 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2197385d91dc..fefe3eafccb9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8718,6 +8718,54 @@ static enum bpf_dynptr_type dynptr_get_type(struct bpf_verifier_env *env,
return state->stack[spi].spilled_ptr.dynptr.type;
}
+static int check_reg_const_str(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg, u32 regno)
+{
+ struct bpf_map *map = reg->map_ptr;
+ int err;
+ int map_off;
+ u64 map_addr;
+ char *str_ptr;
+
+ if (reg->type != PTR_TO_MAP_VALUE)
+ return -EINVAL;
+
+ if (!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,
+ ACCESS_HELPER);
+ 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 0;
+}
+
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
struct bpf_call_arg_meta *meta,
const struct bpf_func_proto *fn,
@@ -8962,44 +9010,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
}
case ARG_PTR_TO_CONST_STR:
{
- struct bpf_map *map = reg->map_ptr;
- int map_off;
- u64 map_addr;
- char *str_ptr;
-
- if (!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,
- ACCESS_HELPER);
+ err = check_reg_const_str(env, reg, regno);
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;
- }
break;
}
case ARG_PTR_TO_KPTR:
--
2.34.1
next prev parent reply other threads:[~2023-11-03 21:46 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-03 21:45 [PATCH v10 bpf-next 0/9] bpf: File verification with LSM and fsverity Song Liu
2023-11-03 21:45 ` [PATCH v10 bpf-next 1/9] bpf: Add __bpf_dynptr_data* for in kernel use Song Liu
2023-11-03 22:02 ` Andrii Nakryiko
2023-11-03 21:45 ` Song Liu [this message]
2023-11-03 22:04 ` [PATCH v10 bpf-next 2/9] bpf: Factor out helper check_reg_const_str() Andrii Nakryiko
2023-11-03 21:45 ` [PATCH v10 bpf-next 3/9] bpf: Introduce KF_ARG_PTR_TO_CONST_STR Song Liu
2023-11-03 22:07 ` Andrii Nakryiko
2023-11-03 21:45 ` [PATCH v10 bpf-next 4/9] bpf: Add kfunc bpf_get_file_xattr Song Liu
2023-11-03 22:10 ` Andrii Nakryiko
2023-11-03 22:30 ` Song Liu
2023-11-03 22:38 ` Song Liu
2023-11-03 22:53 ` Andrii Nakryiko
2023-11-03 21:45 ` [PATCH v10 bpf-next 5/9] bpf, fsverity: Add kfunc bpf_get_fsverity_digest Song Liu
2023-11-03 22:13 ` Andrii Nakryiko
2023-11-03 21:45 ` [PATCH v10 bpf-next 6/9] Documentation/bpf: Add documentation for filesystem kfuncs Song Liu
2023-11-03 21:45 ` [PATCH v10 bpf-next 7/9] selftests/bpf: Sort config in alphabetic order Song Liu
2023-11-03 21:45 ` [PATCH v10 bpf-next 8/9] selftests/bpf: Add tests for filesystem kfuncs Song Liu
2023-11-03 21:45 ` [PATCH v10 bpf-next 9/9] selftests/bpf: Add test that uses fsverity and xattr to sign a file Song Liu
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