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Sat, 04 Apr 2026 11:06:56 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Sat, 04 Apr 2026 14:06:55 -0400 Message-Id: From: "Emil Tsalapatis" To: "Weiming Shi" , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" Cc: "Martin KaFai Lau" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , , "Xiang Mei" Subject: Re: [PATCH bpf v3 0/2] bpf: reject negative CO-RE accessor indices X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260404161221.961828-1-bestswngs@gmail.com> In-Reply-To: <20260404161221.961828-1-bestswngs@gmail.com> On Sat Apr 4, 2026 at 12:12 PM EDT, Weiming Shi wrote: > bpf_core_parse_spec() parses CO-RE accessor strings with sscanf("%d"), > which accepts negative values. The downstream bounds checks only test > the upper bound, so a negative index like -1 slips through, gets cast > to u32 0xffffffff in btf_member_bit_offset(), and crashes the kernel. > > To clarify the kernel-side concern from v2 review: > tools/lib/bpf/relo_core.c is shared code -- the kernel compiles it > directly via kernel/bpf/relo_core.c (#include). So the fix does > apply in the kernel's BPF_PROG_LOAD -> check_core_relo() -> > bpf_core_apply() -> bpf_core_parse_spec() path. > Since this text ends up in the git log, I think you can remove this paragraph - especially since there is no permalink in the version history below. > v3: added selftest (patch 2/2) > v2: fix typo Signed-off-by tag (missing leading 'S') > > Weiming Shi (2): > bpf: reject negative CO-RE accessor indices in bpf_core_parse_spec() > selftests/bpf: add test for negative CO-RE accessor index rejection > > tools/lib/bpf/relo_core.c | 2 + > .../selftests/bpf/prog_tests/core_reloc_raw.c | 94 +++++++++++++++++++ > 2 files changed, 96 insertions(+)