From: Martin KaFai Lau <kafai@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>,
Yonghong Song <yhs@fb.com>
Subject: [PATCH bpf-next 0/4] bpf: Support <8-byte scalar spill and refill
Date: Mon, 20 Sep 2021 18:31:02 -0700 [thread overview]
Message-ID: <20210921013102.1035356-1-kafai@fb.com> (raw)
The verifier currently does not save the reg state when
spilling <8byte bounded scalar to the stack. The bpf program
will be incorrectly rejected when this scalar is refilled to
the reg and then used to offset into a packet header.
The later patch has a simplified bpf prog from a real use case
to demonstrate this case. The current work around is
to reparse the packet again such that this offset scalar
is close to where the packet data will be accessed to
avoid the spill. Thus, the header is parsed twice.
The llvm patch [1] will align the <8bytes spill to
the 8-byte stack address. This set is to make the necessary
changes in verifier to support <8byte scalar spill and refill.
[1] https://reviews.llvm.org/D109073
Martin KaFai Lau (4):
bpf: Check the other end of slot_type for STACK_SPILL
bpf: Support <8-byte scalar spill and refill
bpf: selftest: A bpf prog that has a 32bit scalar spill
bpf: selftest: Add verifier tests for <8-byte scalar spill and refill
kernel/bpf/verifier.c | 97 ++++--
.../selftests/bpf/prog_tests/xdpwall.c | 15 +
tools/testing/selftests/bpf/progs/xdpwall.c | 302 ++++++++++++++++++
.../selftests/bpf/verifier/spill_fill.c | 161 ++++++++++
4 files changed, 549 insertions(+), 26 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/xdpwall.c
create mode 100644 tools/testing/selftests/bpf/progs/xdpwall.c
--
2.30.2
next reply other threads:[~2021-09-21 1:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 1:31 Martin KaFai Lau [this message]
2021-09-21 1:31 ` [PATCH bpf-next 1/4] bpf: Check the other end of slot_type for STACK_SPILL Martin KaFai Lau
2021-09-21 1:31 ` [PATCH bpf-next 2/4] bpf: Support <8-byte scalar spill and refill Martin KaFai Lau
2021-09-21 1:31 ` [PATCH bpf-next 3/4] bpf: selftest: A bpf prog that has a 32bit scalar spill Martin KaFai Lau
2021-09-21 2:32 ` Alexei Starovoitov
2021-09-21 23:52 ` Martin KaFai Lau
2021-09-21 1:31 ` [PATCH bpf-next 4/4] bpf: selftest: Add verifier tests for <8-byte scalar spill and refill Martin KaFai Lau
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