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Mon, 14 Sep 2026 04:50:40 -0700 (PDT) From: Luis Vieira Date: Mon, 14 Sep 2026 08:50:31 -0300 Subject: [PATCH bpf] libbpf: Fix program log buffer size validation Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260914-libbpf-log-buf-fix-v1-1-f592caffcc71@gmail.com> X-B4-Tracking: v=1; b=H4sIAIbfp2oC/x2MSwqAMAwFryJZG2j9oV5FXLSa1kCp0qII4t0NL ucxbx7IlJgyjMUDiS7OvEcBXRawbCZ6Ql6FoVJVpwZdY2BrD4dh92hPh45vbAbXqrpfjGlXkOO RSOY/OoHIML/vBwCA4vppAAAA X-Change-ID: 20260913-libbpf-log-buf-fix-49f5038caa5d To: 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, Luis Vieira X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1789386635; l=2747; i=luisflavieira@gmail.com; s=20260913; h=from:subject:message-id; bh=ChNWu4SF6NGhwjGjf6K8AWy5RuCiogwQwkyEnV0Sbbs=; b=+BXvKW5XIp+uDGQQdXyt3rRGzNHUx/tWoYxQaix3CUebltrheNoWY5mGbtM9eRw81unJKmOjJ ro5a4w4mBlcCM58XPDG+ywgA/kE9F486ggCw81a1k4FN90xIlRpn/Q8 X-Developer-Key: i=luisflavieira@gmail.com; a=ed25519; pk=98MeC/NdrC6ah7zYpPnkWiQIoyj62iUP/rNuV3esCW4= 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 --- 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