linux-kernel - [PATCH bpf v2 0/2] Fix bpf_probe_read_user

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Date:   Wed,  4 Nov 2020 18:25:36 -0800
From:   Daniel Xu <dxu@...uu.xyz>
To:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net
Cc:     Daniel Xu <dxu@...uu.xyz>, kernel-team@...com
Subject: [PATCH bpf v2 0/2] Fix bpf_probe_read_user_str() overcopying

6ae08ae3dea2 ("bpf: Add probe_read_{user, kernel} and probe_read_{user,
kernel}_str helpers") introduced a subtle bug where
bpf_probe_read_user_str() would potentially copy a few extra bytes after
the NUL terminator.

This issue is particularly nefarious when strings are used as map keys,
as seemingly identical strings can occupy multiple entries in a map.

This patchset fixes the issue and introduces a selftest to prevent
future regressions.

Daniel Xu (2):
  lib/strncpy_from_user.c: Don't overcopy bytes after NUL terminator
  selftest/bpf: Test bpf_probe_read_user_str() strips trailing bytes
    after NUL

 lib/strncpy_from_user.c                       |  9 ++-
 .../bpf/prog_tests/probe_read_user_str.c      | 60 +++++++++++++++++++
 .../bpf/progs/test_probe_read_user_str.c      | 34 +++++++++++
 3 files changed, 101 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/probe_read_user_str.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_probe_read_user_str.c

-- 
2.28.0