From: Roberto Sassu <roberto.sassu@huaweicloud.com>
To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
haoluo@google.com, jolsa@kernel.org, mykolal@fb.com,
corbet@lwn.net, dhowells@redhat.com, jarkko@kernel.org,
rostedt@goodmis.org, mingo@redhat.com, paul@paul-moore.com,
jmorris@namei.org, serge@hallyn.com, shuah@kernel.org
Cc: bpf@vger.kernel.org, linux-doc@vger.kernel.org,
keyrings@vger.kernel.org, linux-security-module@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
deso@posteo.net, Roberto Sassu <roberto.sassu@huawei.com>,
Joanne Koong <joannelkoong@gmail.com>
Subject: [PATCH v13 02/10] btf: Handle dynamic pointer parameter in kfuncs
Date: Tue, 23 Aug 2022 17:00:27 +0200 [thread overview]
Message-ID: <20220823150035.711534-3-roberto.sassu@huaweicloud.com> (raw)
In-Reply-To: <20220823150035.711534-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure
that the dynamic pointer is valid and initialized.
To properly detect whether a parameter is of the desired type, introduce
the stringify_struct() macro to compare the returned structure name with
the desired name. In addition, protect against structure renames, by
halting the build with BUILD_BUG_ON(), so that developers have to revisit
the code.
Cc: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
include/linux/bpf_verifier.h | 3 +++
include/linux/btf.h | 9 +++++++++
kernel/bpf/btf.c | 18 ++++++++++++++++++
kernel/bpf/verifier.c | 4 ++--
4 files changed, 32 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 2e3bad8640dc..55876fbdbae2 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -560,6 +560,9 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state
u32 regno);
int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
u32 regno, u32 mem_size);
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type);
/* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
diff --git a/include/linux/btf.h b/include/linux/btf.h
index ad93c2d9cc1c..f546d368ac5d 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -52,6 +52,15 @@
#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
#define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */
+/*
+ * Return the name of the passed struct, if exists, or halt the build if for
+ * example the structure gets renamed. In this way, developers have to revisit
+ * the code using that structure name, and update it accordingly.
+ */
+#define stringify_struct(x) \
+ ({ BUILD_BUG_ON(sizeof(struct x) < 0); \
+ __stringify(x); })
+
struct btf;
struct btf_member;
struct btf_type;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e49b3b6d48ad..26cb548420af 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6362,15 +6362,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
if (is_kfunc) {
bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]);
+ bool arg_dynptr = btf_type_is_struct(ref_t) &&
+ !strcmp(ref_tname,
+ stringify_struct(bpf_dynptr_kern));
/* Permit pointer to mem, but only when argument
* type is pointer to scalar, or struct composed
* (recursively) of scalars.
* When arg_mem_size is true, the pointer can be
* void *.
+ * Also permit initialized dynamic pointers.
*/
if (!btf_type_is_scalar(ref_t) &&
!__btf_type_is_scalar_struct(log, btf, ref_t, 0) &&
+ !arg_dynptr &&
(arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
bpf_log(log,
"arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
@@ -6378,6 +6383,19 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
return -EINVAL;
}
+ if (arg_dynptr) {
+ if (!is_dynptr_reg_valid_init(env, reg,
+ ARG_PTR_TO_DYNPTR)) {
+ bpf_log(log,
+ "arg#%d pointer type %s %s must be initialized\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ continue;
+ }
+
/* Check for mem, len pair */
if (arg_mem_size) {
if (check_kfunc_mem_size_reg(env, ®s[regno + 1], regno + 1)) {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2c1f8069f7b7..aa834e7bb296 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -779,8 +779,8 @@ static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_
return true;
}
-static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
- enum bpf_arg_type arg_type)
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type)
{
struct bpf_func_state *state = func(env, reg);
int spi = get_spi(reg->off);
--
2.25.1
next prev parent reply other threads:[~2022-08-23 17:26 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-23 15:00 [PATCH v13 00/10] bpf: Add kfuncs for PKCS#7 signature verification Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 01/10] bpf: Allow kfuncs to be used in LSM programs Roberto Sassu
2022-08-23 15:00 ` Roberto Sassu [this message]
2022-08-26 20:36 ` [PATCH v13 02/10] btf: Handle dynamic pointer parameter in kfuncs Kumar Kartikeya Dwivedi
2022-08-23 15:00 ` [PATCH v13 03/10] bpf: Export bpf_dynptr_get_size() Roberto Sassu
2022-08-27 23:33 ` KP Singh
2022-08-23 15:00 ` [PATCH v13 04/10] KEYS: Move KEY_LOOKUP_ to include/linux/key.h Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 05/10] bpf: Add bpf_lookup_*_key() and bpf_key_put() kfuncs Roberto Sassu
2022-08-26 5:56 ` Song Liu
2022-08-26 7:21 ` Roberto Sassu
2022-08-26 7:25 ` Song Liu
2022-08-26 7:31 ` Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 06/10] bpf: Add bpf_verify_pkcs7_signature() kfunc Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 07/10] selftests/bpf: Compile kernel with everything as built-in Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 08/10] selftests/bpf: Add verifier tests for bpf_lookup_*_key() and bpf_key_put() Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 09/10] selftests/bpf: Add additional tests for bpf_lookup_*_key() Roberto Sassu
2022-08-23 15:00 ` [PATCH v13 10/10] selftests/bpf: Add test for bpf_verify_pkcs7_signature() kfunc Roberto Sassu
2022-08-25 9:19 ` [PATCH v13 00/10] bpf: Add kfuncs for PKCS#7 signature verification Roberto Sassu
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