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([2620:10d:c092:500::7:35f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-486eb34f353sm26261378f8f.26.2026.09.14.06.22.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Sep 2026 06:22:14 -0700 (PDT) Message-ID: <05221557-59b5-4d93-ac55-d9e372d0862b@gmail.com> Date: Mon, 14 Sep 2026 14:22:13 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf] libbpf: Fix program log buffer size validation To: Luis Vieira , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20260914-libbpf-log-buf-fix-v1-1-f592caffcc71@gmail.com> Content-Language: en-US From: Mykyta Yatsenko In-Reply-To: <20260914-libbpf-log-buf-fix-v1-1-f592caffcc71@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/14/26 12:50 PM, Luis Vieira wrote: > bpf_program__set_log_buf() intends to reject log buffer sizes larger > than UINT_MAX. > > However, the function checks the existing prog->log_size instead of > the incoming log_size argument. As a result, an oversized value can > be accepted. > > Validate the supplied log_size instead. > > Add a regression test that verifies that values larger than UINT_MAX > are rejected with -EINVAL on platforms where size_t can represent > such values. > > Fixes: b3ce90795035 ("libbpf: Add per-program log buffer setter and getter") > Signed-off-by: Luis Vieira > --- The change looks correct, few questions: * Do we really need a unit test for this? We are not testing those error conditions now. * While here should we rewrite the first check as (!!log_buf != !!log_size), to cover the case when log_size == 0 but log_buf is nonnull (we check it later in bpf_prog_load()) (AI) * Fixes tag is probably not needed, because this is libbpf, target bpf-next. > tools/lib/bpf/libbpf.c | 2 +- > tools/testing/selftests/bpf/prog_tests/log_buf.c | 25 ++++++++++++++++++++++++ > 2 files changed, 26 insertions(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index b749c01742ee..e1fed7735614 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -9955,7 +9955,7 @@ int bpf_program__set_log_buf(struct bpf_program *prog, char *log_buf, size_t log > { > if (log_size && !log_buf) > return libbpf_err(-EINVAL); > - if (prog->log_size > UINT_MAX) > + if (log_size > UINT_MAX) > return libbpf_err(-EINVAL); > if (prog->obj->state >= OBJ_LOADED) > return libbpf_err(-EBUSY); > diff --git a/tools/testing/selftests/bpf/prog_tests/log_buf.c b/tools/testing/selftests/bpf/prog_tests/log_buf.c > index d6f14a232002..31c842d27fb4 100644 > --- a/tools/testing/selftests/bpf/prog_tests/log_buf.c > +++ b/tools/testing/selftests/bpf/prog_tests/log_buf.c > @@ -3,6 +3,8 @@ > > #include > #include > +#include > +#include > > #include "test_log_buf.skel.h" > #include "bpf_util.h" > @@ -267,6 +269,27 @@ static void bpf_btf_load_log_buf(void) > btf__free(btf); > } > > +static void prog_log_buf_size_limit(void) > +{ > +#if SIZE_MAX > UINT_MAX > + struct test_log_buf *skel; > + char log_buf[1]; > + int err; > + > + skel = test_log_buf__open(); > + if (!ASSERT_OK_PTR(skel, "skel_open")) > + return; > + > + err = bpf_program__set_log_buf(skel->progs.good_prog, log_buf, > + (size_t)UINT_MAX + 1); > + ASSERT_EQ(err, -EINVAL, "set_log_buf_too_big"); > + > + test_log_buf__destroy(skel); > +#else > + test__skip(); > +#endif > +} > + > void test_log_buf(void) > { > if (test__start_subtest("obj_load_log_buf")) > @@ -275,4 +298,6 @@ void test_log_buf(void) > bpf_prog_load_log_buf(); > if (test__start_subtest("bpf_btf_load_log_buf")) > bpf_btf_load_log_buf(); > + if (test__start_subtest("prog_log_buf_size_limit")) > + prog_log_buf_size_limit(); > } > > --- > base-commit: ee363e055895364039bf28348ff13c615afad4ba > change-id: 20260913-libbpf-log-buf-fix-49f5038caa5d > > Best regards, > -- > Luis Vieira > >