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[34.78.62.124]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3ee0fbc7188sm8551386f8f.37.2025.09.19.07.58.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Sep 2025 07:58:04 -0700 (PDT) From: Ethan Graham To: ethangraham@google.com, glider@google.com Cc: andreyknvl@gmail.com, andy@kernel.org, brauner@kernel.org, brendan.higgins@linux.dev, davem@davemloft.net, davidgow@google.com, dhowells@redhat.com, dvyukov@google.com, elver@google.com, herbert@gondor.apana.org.au, ignat@cloudflare.com, jack@suse.cz, jannh@google.com, johannes@sipsolutions.net, kasan-dev@googlegroups.com, kees@kernel.org, kunit-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lukas@wunner.de, rmoar@google.com, shuah@kernel.org, sj@kernel.org, tarasmadan@google.com Subject: [PATCH v2 08/10] drivers/auxdisplay: add a KFuzzTest for parse_xy() Date: Fri, 19 Sep 2025 14:57:48 +0000 Message-ID: <20250919145750.3448393-9-ethan.w.s.graham@gmail.com> X-Mailer: git-send-email 2.51.0.470.ga7dc726c21-goog In-Reply-To: <20250919145750.3448393-1-ethan.w.s.graham@gmail.com> References: <20250919145750.3448393-1-ethan.w.s.graham@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: BE21D40012 X-Stat-Signature: prcu33expzgdsdfgj7ary9dy5yd6m6sb X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758293886-514842 X-HE-Meta: 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 Pu76zpRg RiBwMrPNhE9WF2NV1Bj4rBZN5ZksXaDUqyW5ai5o2O5TDcpKqCMXztgjWt2Bk1Ymg5xPhGiu4TDw98jemDi3roX841jMOUMNFV1saSV0jklypNiJhOkGcRVN7D1+nQsBvHOfswwhWBT9+2/wE2ydW1lFifyH9CkPu3u1NqweyZjNbnnHOXqOTYk5LXIRsAm7C0/Cy6iNb/KIRdq/Tu9QL8tT5TdmgGrIhO1+y0rfGhAJZPXaxWZZfMYwWjkMO21QJbSQqM9YBS9oIb7R4fpCuAWLUk/6fWGeLbkfGBkfAT+G7hlFyCPI0m8P/OtLewyWAUQ/CLTRllXjSzsm7j9r7QTmZGrhaIEKqvWnE9AjEMjsTxzjnk+i0XT3m4NzkyJl7nZXs6slZoZGQ4a2N2zCWQu5tCCsEKWXu/qA8phijkBB4XsgyjpFvfdQSvR3jJ7a7+/lts3nOZDc/JiM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ethan Graham Add a KFuzzTest fuzzer for the parse_xy() function, located in a new file under /drivers/auxdisplay/tests. To validate the correctness and effectiveness of this KFuzzTest target, a bug was injected into parse_xy() like so: drivers/auxdisplay/charlcd.c:179 - s = p; + s = p + 1; Although a simple off-by-one bug, it requires a specific input sequence in order to trigger it, thus demonstrating the power of pairing KFuzzTest with a coverage-guided fuzzer like syzkaller. Signed-off-by: Ethan Graham --- drivers/auxdisplay/charlcd.c | 8 ++++++++ drivers/auxdisplay/tests/charlcd_kfuzz.c | 20 ++++++++++++++++++++ 2 files changed, 28 insertions(+) create mode 100644 drivers/auxdisplay/tests/charlcd_kfuzz.c diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index 09020bb8ad15..e079b5a9c93c 100644 --- a/drivers/auxdisplay/charlcd.c +++ b/drivers/auxdisplay/charlcd.c @@ -682,3 +682,11 @@ EXPORT_SYMBOL_GPL(charlcd_unregister); MODULE_DESCRIPTION("Character LCD core support"); MODULE_LICENSE("GPL"); + +/* + * When CONFIG_KFUZZTEST is enabled, we include this _kfuzz.c file to ensure + * that KFuzzTest targets are built. + */ +#ifdef CONFIG_KFUZZTEST +#include "tests/charlcd_kfuzz.c" +#endif /* CONFIG_KFUZZTEST */ diff --git a/drivers/auxdisplay/tests/charlcd_kfuzz.c b/drivers/auxdisplay/tests/charlcd_kfuzz.c new file mode 100644 index 000000000000..28ce7069c65c --- /dev/null +++ b/drivers/auxdisplay/tests/charlcd_kfuzz.c @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * charlcd KFuzzTest target + * + * Copyright 2025 Google LLC + */ +#include + +struct parse_xy_arg { + const char *s; +}; + +FUZZ_TEST(test_parse_xy, struct parse_xy_arg) +{ + unsigned long x, y; + + KFUZZTEST_EXPECT_NOT_NULL(parse_xy_arg, s); + KFUZZTEST_ANNOTATE_STRING(parse_xy_arg, s); + parse_xy(arg->s, &x, &y); +} -- 2.51.0.470.ga7dc726c21-goog