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From: Yonghong Song <yhs@fb.com>
To: <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: [PATCH bpf 0/2] bpf: fix a verifier issue when assigning 32bit reg states to 64bit ones
Date: Thu, 28 May 2020 09:50:43 -0700	[thread overview]
Message-ID: <20200528165043.1568623-1-yhs@fb.com> (raw)

Commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking")
added 32bit register states to verifier for explicit ALU32 bounds
tracking. When assigning 32bit register states to 64bit register states,
if 32bit register is a constant value of 0, the 64bit register smax_val
will get U32_MAX(0xffffFFFF). Such an inprecise information may impact
downward verification. Patch #1 has detailed explanation of the program
and how to fix it. Patch #2 provides a verifier test to cover the change.

Yonghong Song (2):
  bpf: fix a verifier issue when assigning 32bit reg states to 64bit
  tools/bpf: add a verifier test for assigning 32bit reg states to 64bit

 kernel/bpf/verifier.c                         |  3 +++
 tools/testing/selftests/bpf/verifier/bounds.c | 22 +++++++++++++++++++
 2 files changed, 25 insertions(+)


             reply	other threads:[~2020-05-28 16:51 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-28 16:50 Yonghong Song [this message]
2020-05-28 16:50 ` [PATCH bpf 1/2] " Yonghong Song
2020-05-28 20:36   ` Alexei Starovoitov
2020-05-28 21:22     ` Yonghong Song
2020-05-28 21:30   ` John Fastabend
2020-05-28 21:58     ` Yonghong Song
2020-05-28 16:50 ` [PATCH bpf 2/2] tools/bpf: add a verifier test for " Yonghong Song

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