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Thu, 03 Sep 2020 08:50:15 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 0838oEp1010972; Thu, 3 Sep 2020 08:50:14 GMT Received: from starbug-mbp.localdomain (/79.97.215.145) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 03 Sep 2020 01:50:13 -0700 Received: by starbug-mbp.localdomain (Postfix, from userid 501) id 154F3134F2E3; Thu, 3 Sep 2020 09:50:10 +0100 (IST) From: Darren Kenny To: Alexander Bulekov , qemu-devel@nongnu.org Subject: Re: [PATCH v2 07/15] fuzz: Add support for custom crossover functions In-Reply-To: <20200819061110.1320568-8-alxndr@bu.edu> References: <20200819061110.1320568-1-alxndr@bu.edu> <20200819061110.1320568-8-alxndr@bu.edu> Date: Thu, 03 Sep 2020 09:50:10 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9732 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 adultscore=0 phishscore=0 malwarescore=0 bulkscore=0 mlxscore=0 mlxlogscore=999 suspectscore=1 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009030081 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9732 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 malwarescore=0 adultscore=0 spamscore=0 mlxscore=0 phishscore=0 impostorscore=0 mlxlogscore=999 bulkscore=0 suspectscore=1 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009030081 Received-SPF: pass client-ip=156.151.31.86; envelope-from=darren.kenny@oracle.com; helo=userp2130.oracle.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/03 04:48:18 X-ACL-Warn: Detected OS = Linux 3.1-3.10 [fuzzy] X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, UNPARSEABLE_RELAY=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laurent Vivier , Thomas Huth , f4bug@amsat.org, Alexander Bulekov , bsd@redhat.com, stefanha@redhat.com, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wednesday, 2020-08-19 at 02:11:02 -04, Alexander Bulekov wrote: > libfuzzer supports a "custom crossover function". Libfuzzer often tries > to blend two inputs to create a new interesting input. Sometimes, we > have a better idea about how to blend inputs together. This change > allows fuzzers to specify a custom function for blending two inputs > together. > > Signed-off-by: Alexander Bulekov Reviewed-by: Darren Kenny > --- > tests/qtest/fuzz/fuzz.c | 13 +++++++++++++ > tests/qtest/fuzz/fuzz.h | 26 ++++++++++++++++++++++++++ > 2 files changed, 39 insertions(+) > > diff --git a/tests/qtest/fuzz/fuzz.c b/tests/qtest/fuzz/fuzz.c > index 8234b68754..248fab5f37 100644 > --- a/tests/qtest/fuzz/fuzz.c > +++ b/tests/qtest/fuzz/fuzz.c > @@ -118,6 +118,19 @@ static FuzzTarget *fuzz_get_target(char* name) > } > > > +/* Sometimes called by libfuzzer to mutate two inputs into one */ > +size_t LLVMFuzzerCustomCrossOver(const uint8_t *data1, size_t size1, > + const uint8_t *data2, size_t size2, > + uint8_t *out, size_t max_out_size, > + unsigned int seed) > +{ > + if(fuzz_target->crossover) { > + return fuzz_target->crossover(data1, size1, data2, size2, out, > + max_out_size, seed); > + } > + return 0; > +} > + > /* Executed for each fuzzing-input */ > int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size) > { > diff --git a/tests/qtest/fuzz/fuzz.h b/tests/qtest/fuzz/fuzz.h > index 9ca3d107c5..d36642b5ec 100644 > --- a/tests/qtest/fuzz/fuzz.h > +++ b/tests/qtest/fuzz/fuzz.h > @@ -77,6 +77,28 @@ typedef struct FuzzTarget { > */ > void(*fuzz)(QTestState *, const unsigned char *, size_t); > > + /* > + * The fuzzer can specify a "Custom Crossover" function for combining two > + * inputs from the corpus. This function is sometimes called by libfuzzer > + * when mutating inputs. > + * > + * data1: location of first input > + * size1: length of first input > + * data1: location of second input > + * size1: length of second input > + * out: where to place the resulting, mutated input > + * max_out_size: the maximum length of the input that can be placed in out > + * seed: the seed that should be used to make mutations deterministic, when needed > + * > + * See libfuzzer's LLVMFuzzerCustomCrossOver API for more info. > + * > + * Can be NULL > + */ > + size_t(*crossover)(const uint8_t *data1, size_t size1, > + const uint8_t *data2, size_t size2, > + uint8_t *out, size_t max_out_size, > + unsigned int seed); > + > } FuzzTarget; > > void flush_events(QTestState *); > @@ -91,6 +113,10 @@ void fuzz_qtest_set_serialize(bool option); > */ > void fuzz_add_target(const FuzzTarget *target); > > +size_t LLVMFuzzerCustomCrossOver(const uint8_t *data1, size_t size1, > + const uint8_t *data2, size_t size2, > + uint8_t *out, size_t max_out_size, > + unsigned int seed); > int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size); > int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp); > > -- > 2.27.0