[v3,bpf,0/2] bpf: return proper error codes for lwt redirect

Message

Yan Zhai July 25, 2023, 4:12 a.m. UTC

lwt xmit hook does not expect positive return values in function
ip_finish_output2 and ip6_finish_output2. However, BPF redirect programs
can return positive values such like NET_XMIT_DROP, NET_RX_DROP, and etc
as errors. Such return values can panic the kernel unexpectedly:

https://gist.github.com/zhaiyan920/8fbac245b261fe316a7ef04c9b1eba48

This patch fixes the return values from BPF redirect, so the error
handling would be consistent at xmit hook. It also adds a few test cases
to prevent future regressions.

v2: https://lore.kernel.org/netdev/[e-mail]/ 
v1: https://lore.kernel.org/bpf/[e-mail]/

changes since v2:
  * subject name changed
  * also covered redirect to ingress case
  * added selftests

changes since v1:
  * minor code style changes

Yan Zhai (2):
  bpf: fix skb_do_redirect return values
  bpf: selftests: add lwt redirect regression test cases

 net/core/filter.c                             |  12 +-
 tools/testing/selftests/bpf/Makefile          |   1 +
 .../selftests/bpf/progs/test_lwt_redirect.c   |  67 +++++++
 .../selftests/bpf/test_lwt_redirect.sh        | 165 ++++++++++++++++++
 4 files changed, 244 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_lwt_redirect.c
 create mode 100755 tools/testing/selftests/bpf/test_lwt_redirect.sh

Comments

Jakub Sitnicki July 25, 2023, 1:20 p.m. UTC | #1

On Mon, Jul 24, 2023 at 09:12 PM -07, Yan Zhai wrote:
> lwt xmit hook does not expect positive return values in function
> ip_finish_output2 and ip6_finish_output2. However, BPF redirect programs
> can return positive values such like NET_XMIT_DROP, NET_RX_DROP, and etc
> as errors. Such return values can panic the kernel unexpectedly:
>
> https://gist.github.com/zhaiyan920/8fbac245b261fe316a7ef04c9b1eba48
>
> This patch fixes the return values from BPF redirect, so the error
> handling would be consistent at xmit hook. It also adds a few test cases
> to prevent future regressions.
>
> v2: https://lore.kernel.org/netdev/[e-mail]/ 
> v1: https://lore.kernel.org/bpf/[e-mail]/
>
> changes since v2:
>   * subject name changed
>   * also covered redirect to ingress case
>   * added selftests
>
> changes since v1:
>   * minor code style changes
>
> Yan Zhai (2):
>   bpf: fix skb_do_redirect return values
>   bpf: selftests: add lwt redirect regression test cases
>
>  net/core/filter.c                             |  12 +-
>  tools/testing/selftests/bpf/Makefile          |   1 +
>  .../selftests/bpf/progs/test_lwt_redirect.c   |  67 +++++++
>  .../selftests/bpf/test_lwt_redirect.sh        | 165 ++++++++++++++++++
>  4 files changed, 244 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/bpf/progs/test_lwt_redirect.c
>  create mode 100755 tools/testing/selftests/bpf/test_lwt_redirect.sh

For the series:

Tested-by: Jakub Sitnicki <[e-mail]>