linux-kernel - [PATCH v3 0/2] bpf, verifier: Improve precision of BPF_ADD and BPF

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Message-ID: <20250623040359.343235-1-harishankar.vishwanathan@gmail.com>
Date: Mon, 23 Jun 2025 00:03:55 -0400
From: Harishankar Vishwanathan <harishankar.vishwanathan@...il.com>
To: ast@...nel.org
Cc: m.shachnai@...gers.edu,
	srinivas.narayana@...gers.edu,
	santosh.nagarakatte@...gers.edu,
	Harishankar Vishwanathan <harishankar.vishwanathan@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/2] bpf, verifier: Improve precision of BPF_ADD and BPF_SUB

This patchset improves the precision of BPF_ADD and BPF_SUB range
tracking. It also adds selftests that exercise the cases where precision
improvement occurs, and selftests for the cases where precise bounds
cannot be computed and the output register state values are set to
unbounded.

Changelog:

v3:
* Improve readability in selftests and commit message by using
  more readable constants (suggested by Eduard Zingerman).
* Add four new selftests for the cases where precise output register
  state bounds cannot be computed in scalar(32)_min_max_add/sub, so the
  output register state must be set to unbounded, i.e., [0, U64_MAX]
  or [0, U32_MAX].
* Add suggested-by Eduard tag to commit message for changes to
  verifier_bounds.c

v2:
* Add clearer example of precision improvement in the commit message for
  verifier.c changes.
* Add selftests that exercise the precision improvement to
  verifier_bounds.c (suggested by Eduard Zingerman).

v1:
  https://lore.kernel.org/bpf/20250610221356.2663491-1-harishankar.vishwanathan@gmail.com/

Harishankar Vishwanathan (2):
  bpf, verifier: Improve precision for BPF_ADD and BPF_SUB
  selftests/bpf: Add testcases for BPF_ADD and BPF_SUB

 kernel/bpf/verifier.c                         |  76 ++++++---
 .../selftests/bpf/progs/verifier_bounds.c     | 161 ++++++++++++++++++
 2 files changed, 217 insertions(+), 20 deletions(-)

-- 
2.45.2