diff mbox series

[v11,2/9] btf: Handle dynamic pointer parameter in kfuncs

Message ID 20220812101902.2846182-3-roberto.sassu@huawei.com (mailing list archive)
State New
Headers show
Series bpf: Add kfuncs for PKCS#7 signature verification | expand

Commit Message

Roberto Sassu Aug. 12, 2022, 10:18 a.m. UTC
Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure
that the dynamic pointer is valid and initialized.

Cc: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 include/linux/bpf_verifier.h |  3 +++
 kernel/bpf/btf.c             | 22 ++++++++++++++++++++++
 kernel/bpf/verifier.c        |  4 ++--
 3 files changed, 27 insertions(+), 2 deletions(-)

Comments

Daniel Borkmann Aug. 15, 2022, 4:45 p.m. UTC | #1
On 8/12/22 12:18 PM, Roberto Sassu wrote:
> Allow the bpf_dynptr_kern parameter to be specified in kfuncs. Also, ensure
> that the dynamic pointer is valid and initialized.
> 
> Cc: Joanne Koong <joannelkoong@gmail.com>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>   include/linux/bpf_verifier.h |  3 +++
>   kernel/bpf/btf.c             | 22 ++++++++++++++++++++++
>   kernel/bpf/verifier.c        |  4 ++--
>   3 files changed, 27 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/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index e49b3b6d48ad..86e63f2ee5da 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -195,6 +195,10 @@
>   	     i < btf_type_vlen(struct_type);					\
>   	     i++, member++)
>   
> +#define stringify_struct(x)			\
> +	({ BUILD_BUG_ON(sizeof(struct x) < 0);	\
> +	   __stringify(x); })
> +

I'd say lets move this to include/linux/btf.h with a comment explaining the BUILD_BUG_ON()
which ensures the struct actually exits.

If there's ever use outside of BTF, it could be relocated to include/linux/stringify.h.

>   DEFINE_IDR(btf_idr);
>   DEFINE_SPINLOCK(btf_idr_lock);
>
diff mbox series

Patch

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/kernel/bpf/btf.c b/kernel/bpf/btf.c
index e49b3b6d48ad..86e63f2ee5da 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -195,6 +195,10 @@ 
 	     i < btf_type_vlen(struct_type);					\
 	     i++, member++)
 
+#define stringify_struct(x)			\
+	({ BUILD_BUG_ON(sizeof(struct x) < 0);	\
+	   __stringify(x); })
+
 DEFINE_IDR(btf_idr);
 DEFINE_SPINLOCK(btf_idr_lock);
 
@@ -6362,15 +6366,20 @@  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], &regs[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 +6387,19 @@  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, &regs[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);