netdev - [PATCH bpf-next 0/3] bpf: Pointers beyond packet end.

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Message-Id: <20201021182015.39000-1-alexei.starovoitov@gmail.com>
Date:   Wed, 21 Oct 2020 11:20:12 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, john.fastabend@...il.com, jolsa@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH bpf-next 0/3] bpf: Pointers beyond packet end.

From: Alexei Starovoitov <ast@...nel.org>

In some cases LLVM uses the knowledge that branch is taken to optimze the code
which causes the verifier to reject valid programs.
Teach the verifier to recognize that
r1 = skb->data;
r1 += 10;
r2 = skb->data_end;
if (r1 > r2) {
  here r1 points beyond packet_end and subsequent
  if (r1 > r2) // always evaluates to "true".
}

Alexei Starovoitov (3):
  bpf: Support for pointers beyond pkt_end.
  selftests/bpf: Add skb_pkt_end test
  selftests/bpf: Add asm tests for pkt vs pkt_end comparison.

 include/linux/bpf_verifier.h                  |   2 +-
 kernel/bpf/verifier.c                         | 131 +++++++++++++++---
 .../bpf/prog_tests/test_skb_pkt_end.c         |  41 ++++++
 .../testing/selftests/bpf/progs/skb_pkt_end.c |  54 ++++++++
 .../testing/selftests/bpf/verifier/ctx_skb.c  |  42 ++++++
 5 files changed, 247 insertions(+), 23 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_skb_pkt_end.c
 create mode 100644 tools/testing/selftests/bpf/progs/skb_pkt_end.c

-- 
2.23.0