[PATCH bpf-next v3 0/3] Enlarge offset check value in bpf_skb_load_bytes

[PATCH bpf-next v3 0/3] Enlarge offset check value in bpf_skb_load_bytes

[Liu Jian]

The data length of skb frags + frag_list may be greater than 0xffff,
and skb_header_pointer can not handle negative offset and negative len.
So here INT_MAX is used to check the validity of offset and len.

And add the test case for the change.

Liu Jian (3):
  net: Enlarge offset check value from 0xffff to INT_MAX in
    bpf_skb_load_bytes
  net: change skb_ensure_writable()'s write_len param to unsigned int
    type
  selftests: bpf: add test for skb_load_bytes

 include/linux/skbuff.h                        |  2 +-
 net/core/filter.c                             |  4 +-
 net/core/skbuff.c                             |  2 +-
 .../selftests/bpf/prog_tests/skb_load_bytes.c | 45 +++++++++++++++++++
 .../selftests/bpf/progs/skb_load_bytes.c      | 19 ++++++++
 5 files changed, 68 insertions(+), 4 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
 create mode 100644 tools/testing/selftests/bpf/progs/skb_load_bytes.c

-- 
2.17.1

[PATCH bpf-next v3 1/3] net: Enlarge offset check value from 0xffff to INT_MAX in bpf_skb_load_bytes

[Liu Jian]

The data length of skb frags + frag_list may be greater than 0xffff,
and skb_header_pointer can not handle negative offset and negative len.
So here INT_MAX is used to check the validity of offset and len.
Add the same change to the related function skb_store_bytes.

Fixes: 05c74e5e53f6 ("bpf: add bpf_skb_load_bytes helper")
Signed-off-by: Liu Jian <liujian56@huawei.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
v2->v3: change nothing
 net/core/filter.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 64470a727ef7..1571b6bc51ea 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1687,7 +1687,7 @@ BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff *, skb, u32, offset,
 
 	if (unlikely(flags & ~(BPF_F_RECOMPUTE_CSUM | BPF_F_INVALIDATE_HASH)))
 		return -EINVAL;
-	if (unlikely(offset > 0xffff))
+	if (unlikely(offset > INT_MAX || len > INT_MAX))
 		return -EFAULT;
 	if (unlikely(bpf_try_make_writable(skb, offset + len)))
 		return -EFAULT;
@@ -1722,7 +1722,7 @@ BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
 {
 	void *ptr;
 
-	if (unlikely(offset > 0xffff))
+	if (unlikely(offset > INT_MAX || len > INT_MAX))
 		goto err_clear;
 
 	ptr = skb_header_pointer(skb, offset, len, to);
-- 
2.17.1

[PATCH bpf-next v3 2/3] net: change skb_ensure_writable()'s write_len param to unsigned int type

[Liu Jian]

Both pskb_may_pull() and skb_clone_writable()'s length parameters are of
type unsigned int already.
Therefore, change this function's write_len param to unsigned int type.

Signed-off-by: Liu Jian <liujian56@huawei.com>
---
 include/linux/skbuff.h | 2 +-
 net/core/skbuff.c      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3a30cae8b0a5..fe8990ce52a8 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3886,7 +3886,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
 struct sk_buff *skb_segment_list(struct sk_buff *skb, netdev_features_t features,
 				 unsigned int offset);
 struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
-int skb_ensure_writable(struct sk_buff *skb, int write_len);
+int skb_ensure_writable(struct sk_buff *skb, unsigned int write_len);
 int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci);
 int skb_vlan_pop(struct sk_buff *skb);
 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 30b523fa4ad2..a84e00e44ad2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5601,7 +5601,7 @@ struct sk_buff *skb_vlan_untag(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(skb_vlan_untag);
 
-int skb_ensure_writable(struct sk_buff *skb, int write_len)
+int skb_ensure_writable(struct sk_buff *skb, unsigned int write_len)
 {
 	if (!pskb_may_pull(skb, write_len))
 		return -ENOMEM;
-- 
2.17.1

[PATCH bpf-next v3 3/3] selftests: bpf: add test for skb_load_bytes

[Liu Jian]

Use bpf_prog_test_run_opts to test the skb_load_bytes function.
Tests the behavior when offset is greater than INT_MAX or a normal value.

Signed-off-by: Liu Jian <liujian56@huawei.com>
---
v2->v3: Change patch prefix to bpf-next. Use ASSERT_* calls
 .../selftests/bpf/prog_tests/skb_load_bytes.c | 45 +++++++++++++++++++
 .../selftests/bpf/progs/skb_load_bytes.c      | 19 ++++++++
 2 files changed, 64 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
 create mode 100644 tools/testing/selftests/bpf/progs/skb_load_bytes.c

diff --git a/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c b/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
new file mode 100644
index 000000000000..d7f83c0a40a5
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "skb_load_bytes.skel.h"
+
+void test_skb_load_bytes(void)
+{
+	struct skb_load_bytes *skel;
+	int err, prog_fd, test_result;
+	struct __sk_buff skb = { 0 };
+
+	LIBBPF_OPTS(bpf_test_run_opts, tattr,
+		.data_in = &pkt_v4,
+		.data_size_in = sizeof(pkt_v4),
+		.ctx_in = &skb,
+		.ctx_size_in = sizeof(skb),
+	);
+
+	skel = skb_load_bytes__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		return;
+
+	prog_fd = bpf_program__fd(skel->progs.skb_process);
+	if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
+		goto out;
+
+	skel->bss->load_offset = (uint32_t)(-1);
+	err = bpf_prog_test_run_opts(prog_fd, &tattr);
+	if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
+		goto out;
+	test_result = skel->bss->test_result;
+	if (!ASSERT_EQ(test_result, -EFAULT, "offset -1"))
+		goto out;
+
+	skel->bss->load_offset = (uint32_t)10;
+	err = bpf_prog_test_run_opts(prog_fd, &tattr);
+	if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
+		goto out;
+	test_result = skel->bss->test_result;
+	if (!ASSERT_EQ(test_result, 0, "offset 10"))
+		goto out;
+
+out:
+	skb_load_bytes__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/skb_load_bytes.c b/tools/testing/selftests/bpf/progs/skb_load_bytes.c
new file mode 100644
index 000000000000..e4252fd973be
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/skb_load_bytes.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+__u32 load_offset = 0;
+int test_result = 0;
+
+SEC("tc")
+int skb_process(struct __sk_buff *skb)
+{
+	char buf[16];
+
+	test_result = bpf_skb_load_bytes(skb, load_offset, buf, 10);
+
+	return 0;
+}
-- 
2.17.1

Re: [PATCH bpf-next v3 2/3] net: change skb_ensure_writable()'s write_len param to unsigned int type

[Song Liu]

> On Apr 14, 2022, at 6:59 AM, Liu Jian <liujian56@huawei.com> wrote:
> 
> Both pskb_may_pull() and skb_clone_writable()'s length parameters are of
> type unsigned int already.
> Therefore, change this function's write_len param to unsigned int type.
> 
> Signed-off-by: Liu Jian <liujian56@huawei.com>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
> include/linux/skbuff.h | 2 +-
> net/core/skbuff.c      | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 3a30cae8b0a5..fe8990ce52a8 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -3886,7 +3886,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
> struct sk_buff *skb_segment_list(struct sk_buff *skb, netdev_features_t features,
> 				 unsigned int offset);
> struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
> -int skb_ensure_writable(struct sk_buff *skb, int write_len);
> +int skb_ensure_writable(struct sk_buff *skb, unsigned int write_len);
> int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci);
> int skb_vlan_pop(struct sk_buff *skb);
> int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 30b523fa4ad2..a84e00e44ad2 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5601,7 +5601,7 @@ struct sk_buff *skb_vlan_untag(struct sk_buff *skb)
> }
> EXPORT_SYMBOL(skb_vlan_untag);
> 
> -int skb_ensure_writable(struct sk_buff *skb, int write_len)
> +int skb_ensure_writable(struct sk_buff *skb, unsigned int write_len)
> {
> 	if (!pskb_may_pull(skb, write_len))
> 		return -ENOMEM;
> -- 
> 2.17.1
> 

Re: [PATCH bpf-next v3 3/3] selftests: bpf: add test for skb_load_bytes

[Song Liu]

> On Apr 14, 2022, at 6:59 AM, Liu Jian <liujian56@huawei.com> wrote:
> 
> Use bpf_prog_test_run_opts to test the skb_load_bytes function.
> Tests the behavior when offset is greater than INT_MAX or a normal value.
> 
> Signed-off-by: Liu Jian <liujian56@huawei.com>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
> v2->v3: Change patch prefix to bpf-next. Use ASSERT_* calls
> .../selftests/bpf/prog_tests/skb_load_bytes.c | 45 +++++++++++++++++++
> .../selftests/bpf/progs/skb_load_bytes.c      | 19 ++++++++
> 2 files changed, 64 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
> create mode 100644 tools/testing/selftests/bpf/progs/skb_load_bytes.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c b/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
> new file mode 100644
> index 000000000000..d7f83c0a40a5
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/skb_load_bytes.c
> @@ -0,0 +1,45 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +#include "skb_load_bytes.skel.h"
> +
> +void test_skb_load_bytes(void)
> +{
> +	struct skb_load_bytes *skel;
> +	int err, prog_fd, test_result;
> +	struct __sk_buff skb = { 0 };
> +
> +	LIBBPF_OPTS(bpf_test_run_opts, tattr,
> +		.data_in = &pkt_v4,
> +		.data_size_in = sizeof(pkt_v4),
> +		.ctx_in = &skb,
> +		.ctx_size_in = sizeof(skb),
> +	);
> +
> +	skel = skb_load_bytes__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
> +		return;
> +
> +	prog_fd = bpf_program__fd(skel->progs.skb_process);
> +	if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
> +		goto out;
> +
> +	skel->bss->load_offset = (uint32_t)(-1);
> +	err = bpf_prog_test_run_opts(prog_fd, &tattr);
> +	if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
> +		goto out;
> +	test_result = skel->bss->test_result;
> +	if (!ASSERT_EQ(test_result, -EFAULT, "offset -1"))
> +		goto out;
> +
> +	skel->bss->load_offset = (uint32_t)10;
> +	err = bpf_prog_test_run_opts(prog_fd, &tattr);
> +	if (!ASSERT_OK(err, "bpf_prog_test_run_opts"))
> +		goto out;
> +	test_result = skel->bss->test_result;
> +	if (!ASSERT_EQ(test_result, 0, "offset 10"))
> +		goto out;
> +
> +out:
> +	skb_load_bytes__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/skb_load_bytes.c b/tools/testing/selftests/bpf/progs/skb_load_bytes.c
> new file mode 100644
> index 000000000000..e4252fd973be
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/skb_load_bytes.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +__u32 load_offset = 0;
> +int test_result = 0;
> +
> +SEC("tc")
> +int skb_process(struct __sk_buff *skb)
> +{
> +	char buf[16];
> +
> +	test_result = bpf_skb_load_bytes(skb, load_offset, buf, 10);
> +
> +	return 0;
> +}
> -- 
> 2.17.1
> 

Re: [PATCH bpf-next v3 1/3] net: Enlarge offset check value from 0xffff to INT_MAX in bpf_skb_load_bytes

[Daniel Borkmann]

On 4/14/22 3:59 PM, Liu Jian wrote:
> The data length of skb frags + frag_list may be greater than 0xffff,
> and skb_header_pointer can not handle negative offset and negative len.
> So here INT_MAX is used to check the validity of offset and len.
> Add the same change to the related function skb_store_bytes.
> 
> Fixes: 05c74e5e53f6 ("bpf: add bpf_skb_load_bytes helper")
> Signed-off-by: Liu Jian <liujian56@huawei.com>
> Acked-by: Song Liu <songliubraving@fb.com>
> ---
> v2->v3: change nothing
>   net/core/filter.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 64470a727ef7..1571b6bc51ea 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -1687,7 +1687,7 @@ BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff *, skb, u32, offset,
>   
>   	if (unlikely(flags & ~(BPF_F_RECOMPUTE_CSUM | BPF_F_INVALIDATE_HASH)))
>   		return -EINVAL;
> -	if (unlikely(offset > 0xffff))
> +	if (unlikely(offset > INT_MAX || len > INT_MAX))

One more follow-up question, len param is checked by the verifier for the provided buffer.
Why is it needed here? Were you able to create e.g. map values of size larger than INT_MAX?
Please provide details. (Other than that, rest looks good.)

>   		return -EFAULT;
>   	if (unlikely(bpf_try_make_writable(skb, offset + len)))
>   		return -EFAULT;
> @@ -1722,7 +1722,7 @@ BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
>   {
>   	void *ptr;
>   
> -	if (unlikely(offset > 0xffff))
> +	if (unlikely(offset > INT_MAX || len > INT_MAX))
>   		goto err_clear;
>   
>   	ptr = skb_header_pointer(skb, offset, len, to);
> 

RE: [PATCH bpf-next v3 1/3] net: Enlarge offset check value from 0xffff to INT_MAX in bpf_skb_load_bytes

[liujian (CE)]

> -----Original Message-----
> From: Daniel Borkmann [mailto:daniel@iogearbox.net]
> Sent: Saturday, April 16, 2022 3:32 AM
> To: liujian (CE) <liujian56@huawei.com>; ast@kernel.org; andrii@kernel.org;
> kafai@fb.com; songliubraving@fb.com; yhs@fb.com;
> john.fastabend@gmail.com; kpsingh@kernel.org; davem@davemloft.net;
> kuba@kernel.org; sdf@google.com; netdev@vger.kernel.org;
> bpf@vger.kernel.org; pabeni@redhat.com
> Subject: Re: [PATCH bpf-next v3 1/3] net: Enlarge offset check value from
> 0xffff to INT_MAX in bpf_skb_load_bytes
> 
> On 4/14/22 3:59 PM, Liu Jian wrote:
> > The data length of skb frags + frag_list may be greater than 0xffff,
> > and skb_header_pointer can not handle negative offset and negative len.
> > So here INT_MAX is used to check the validity of offset and len.
> > Add the same change to the related function skb_store_bytes.
> >
> > Fixes: 05c74e5e53f6 ("bpf: add bpf_skb_load_bytes helper")
> > Signed-off-by: Liu Jian <liujian56@huawei.com>
> > Acked-by: Song Liu <songliubraving@fb.com>
> > ---
> > v2->v3: change nothing
> >   net/core/filter.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/core/filter.c b/net/core/filter.c index
> > 64470a727ef7..1571b6bc51ea 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -1687,7 +1687,7 @@ BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff
> > *, skb, u32, offset,
> >
> >   	if (unlikely(flags & ~(BPF_F_RECOMPUTE_CSUM |
> BPF_F_INVALIDATE_HASH)))
> >   		return -EINVAL;
> > -	if (unlikely(offset > 0xffff))
> > +	if (unlikely(offset > INT_MAX || len > INT_MAX))
> 
> One more follow-up question, len param is checked by the verifier for the
> provided buffer.
> Why is it needed here? Were you able to create e.g. map values of size larger
> than INT_MAX?
> Please provide details. (Other than that, rest looks good.)
> 
I only need change "offset > 0xffff".  Delete " || len > INT_MAX " in v4.
Thank you~

> >   		return -EFAULT;
> >   	if (unlikely(bpf_try_make_writable(skb, offset + len)))
> >   		return -EFAULT;
> > @@ -1722,7 +1722,7 @@ BPF_CALL_4(bpf_skb_load_bytes, const struct
> sk_buff *, skb, u32, offset,
> >   {
> >   	void *ptr;
> >
> > -	if (unlikely(offset > 0xffff))
> > +	if (unlikely(offset > INT_MAX || len > INT_MAX))
> >   		goto err_clear;
> >
> >   	ptr = skb_header_pointer(skb, offset, len, to);
> >