diff mbox series

[v8,bpf-next,1/9] bpf: Add __bpf_dynptr_data* for in kernel use

Message ID 20231102201619.3135203-2-song@kernel.org (mailing list archive)
State Superseded
Headers show
Series bpf: File verification with LSM and fsverity | expand

Commit Message

Song Liu Nov. 2, 2023, 8:16 p.m. UTC 
Different types of bpf dynptr have different internal data storage.
Specifically, SKB and XDP type of dynptr may have non-continuous data.
Therefore, it is not always safe to directly access dynptr->data.

Add __bpf_dynptr_data and __bpf_dynptr_data_rw to replace direct access to
dynptr->data.

Update bpf_verify_pkcs7_signature to use __bpf_dynptr_data instead of
dynptr->data.

Signed-off-by: Song Liu <song@kernel.org>
---
 include/linux/bpf.h      |  2 ++
 kernel/bpf/helpers.c     | 47 ++++++++++++++++++++++++++++++++++++++++
 kernel/trace/bpf_trace.c | 13 +++++++----
 3 files changed, 58 insertions(+), 4 deletions(-)

Comments

Song Liu Nov. 2, 2023, 10:59 p.m. UTC | #1 
On Thu, Nov 2, 2023 at 1:16 PM Song Liu <song@kernel.org> wrote:
>
[...]
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index df697c74d519..92dc20d9b9ae 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1378,6 +1378,7 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
>                                struct bpf_dynptr_kern *sig_ptr,
>                                struct bpf_key *trusted_keyring)
>  {
> +       void *data, *sig;
>         int ret;
>
>         if (trusted_keyring->has_ref) {
> @@ -1394,10 +1395,14 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
>                         return ret;
>         }
>
> -       return verify_pkcs7_signature(data_ptr->data,
> -                                     __bpf_dynptr_size(data_ptr),
> -                                     sig_ptr->data,
> -                                     __bpf_dynptr_size(sig_ptr),
> +       data = __bpf_dynptr_data(data_ptr, __bpf_dynptr_size(data_ptr));
> +       sig = __bpf_dynptr_data(sig_ptr, __bpf_dynptr_size(sig_ptr));
> +
> +       if (!data || !sig)
> +               return -EINVAL;

Sigh, I missed this failure:

https://github.com/kernel-patches/bpf/actions/runs/6737884115/job/18316480188

#110/1 kfunc_dynptr_param/dynptr_data_null
...
verify_success:FAIL:err unexpected err: actual -22 != expected -74

It is easy to fix, but I am not sure which is the right fix.

Basically, null dynptr bpf_verify_pkcs7_signature used to return
-EBADMSG. And it
is returning -EINVAL after this change. Do we need to keep the error code as
-EBADMSG?

Thanks,
Song

> +
> +       return verify_pkcs7_signature(data, __bpf_dynptr_size(data_ptr),
> +                                     sig, __bpf_dynptr_size(sig_ptr),
>                                       trusted_keyring->key,
>                                       VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
>                                       NULL);
> --
> 2.34.1
>
>
Song Liu Nov. 2, 2023, 11:53 p.m. UTC | #2 
Hi Roberto,

On Thu, Nov 2, 2023 at 3:59 PM Song Liu <song@kernel.org> wrote:
>
> On Thu, Nov 2, 2023 at 1:16 PM Song Liu <song@kernel.org> wrote:
> >
> [...]
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index df697c74d519..92dc20d9b9ae 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1378,6 +1378,7 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
> >                                struct bpf_dynptr_kern *sig_ptr,
> >                                struct bpf_key *trusted_keyring)
> >  {
> > +       void *data, *sig;
> >         int ret;
> >
> >         if (trusted_keyring->has_ref) {
> > @@ -1394,10 +1395,14 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
> >                         return ret;
> >         }
> >
> > -       return verify_pkcs7_signature(data_ptr->data,
> > -                                     __bpf_dynptr_size(data_ptr),
> > -                                     sig_ptr->data,
> > -                                     __bpf_dynptr_size(sig_ptr),
> > +       data = __bpf_dynptr_data(data_ptr, __bpf_dynptr_size(data_ptr));
> > +       sig = __bpf_dynptr_data(sig_ptr, __bpf_dynptr_size(sig_ptr));
> > +
> > +       if (!data || !sig)
> > +               return -EINVAL;
>
> Sigh, I missed this failure:
>
> https://github.com/kernel-patches/bpf/actions/runs/6737884115/job/18316480188
>
> #110/1 kfunc_dynptr_param/dynptr_data_null
> ...
> verify_success:FAIL:err unexpected err: actual -22 != expected -74
>
> It is easy to fix, but I am not sure which is the right fix.
>
> Basically, null dynptr bpf_verify_pkcs7_signature used to return
> -EBADMSG. And it
> is returning -EINVAL after this change. Do we need to keep the error code as
> -EBADMSG?

Could you please share your thoughts on this (EINVAL vs. EBADMSG)?

Thanks,
Song
diff mbox series

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b4825d3cdb29..129c5a7c5982 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1222,6 +1222,8 @@  enum bpf_dynptr_type {
 
 int bpf_dynptr_check_size(u32 size);
 u32 __bpf_dynptr_size(const struct bpf_dynptr_kern *ptr);
+void *__bpf_dynptr_data(const struct bpf_dynptr_kern *ptr, u32 len);
+void *__bpf_dynptr_data_rw(const struct bpf_dynptr_kern *ptr, u32 len);
 
 #ifdef CONFIG_BPF_JIT
 int bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_trampoline *tr);
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index e46ac288a108..ddd1a5a81652 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2611,3 +2611,50 @@  static int __init kfunc_init(void)
 }
 
 late_initcall(kfunc_init);
+
+/* Get a pointer to dynptr data up to len bytes for read only access. If
+ * the dynptr doesn't have continuous data up to len bytes, return NULL.
+ */
+void *__bpf_dynptr_data(const struct bpf_dynptr_kern *ptr, u32 len)
+{
+	enum bpf_dynptr_type type;
+	int err;
+
+	if (!ptr->data)
+		return NULL;
+
+	err = bpf_dynptr_check_off_len(ptr, 0, len);
+	if (err)
+		return NULL;
+	type = bpf_dynptr_get_type(ptr);
+
+	switch (type) {
+	case BPF_DYNPTR_TYPE_LOCAL:
+	case BPF_DYNPTR_TYPE_RINGBUF:
+		return ptr->data + ptr->offset;
+	case BPF_DYNPTR_TYPE_SKB:
+		return skb_pointer_if_linear(ptr->data, ptr->offset, len);
+	case BPF_DYNPTR_TYPE_XDP:
+	{
+		void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset, len);
+
+		if (IS_ERR_OR_NULL(xdp_ptr))
+			return NULL;
+		return xdp_ptr;
+	}
+	default:
+		WARN_ONCE(true, "unknown dynptr type %d\n", type);
+		return NULL;
+	}
+}
+
+/* Get a pointer to dynptr data up to len bytes for read write access. If
+ * the dynptr doesn't have continuous data up to len bytes, or the dynptr
+ * is read only, return NULL.
+ */
+void *__bpf_dynptr_data_rw(const struct bpf_dynptr_kern *ptr, u32 len)
+{
+	if (__bpf_dynptr_is_rdonly(ptr))
+		return NULL;
+	return __bpf_dynptr_data(ptr, len);
+}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index df697c74d519..92dc20d9b9ae 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1378,6 +1378,7 @@  __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 			       struct bpf_dynptr_kern *sig_ptr,
 			       struct bpf_key *trusted_keyring)
 {
+	void *data, *sig;
 	int ret;
 
 	if (trusted_keyring->has_ref) {
@@ -1394,10 +1395,14 @@  __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
 			return ret;
 	}
 
-	return verify_pkcs7_signature(data_ptr->data,
-				      __bpf_dynptr_size(data_ptr),
-				      sig_ptr->data,
-				      __bpf_dynptr_size(sig_ptr),
+	data = __bpf_dynptr_data(data_ptr, __bpf_dynptr_size(data_ptr));
+	sig = __bpf_dynptr_data(sig_ptr, __bpf_dynptr_size(sig_ptr));
+
+	if (!data || !sig)
+		return -EINVAL;
+
+	return verify_pkcs7_signature(data, __bpf_dynptr_size(data_ptr),
+				      sig, __bpf_dynptr_size(sig_ptr),
 				      trusted_keyring->key,
 				      VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
 				      NULL);