Merge remote-tracking branch 'remotes/huth-gitlab/tags/pull-request-2020-07-21' into staging

* Fix memory leak in fuzzer
* Fuzzer documentation updates
* Some other minor fuzzer updates
* Fix "make check-qtest SPEED=slow" (bug in msf2 instance_init)

# gpg: Signature made Tue 21 Jul 2020 07:48:10 BST
# gpg:                using RSA key 27B88847EEE0250118F3EAB92ED9D774FE702DB5
# gpg:                issuer "thuth@redhat.com"
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg:                 aka "Thomas Huth <thuth@redhat.com>" [full]
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>" [full]
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>" [unknown]
# Primary key fingerprint: 27B8 8847 EEE0 2501 18F3  EAB9 2ED9 D774 FE70 2DB5

* remotes/huth-gitlab/tags/pull-request-2020-07-21:
  hw: Mark nd_table[] misuse in realize methods FIXME
  msf2: Unbreak device-list-properties for "msf-soc"
  MAINTAINERS: Extend the device fuzzing section
  docs/fuzz: add instructions for generating a coverage report
  docs/fuzz: add information about useful libFuzzer flags
  docs/fuzz: describe building fuzzers with enable-sanitizers
  fuzz: build without AddressSanitizer, by default
  gitlab-ci.yml: Add oss-fuzz build tests
  fuzz: Fix leak when assembling datadir path string
  scripts/oss-fuzz: Limit target list to i386-softmmu
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

.gitlab-ci.yml

@@ -164,22 +164,20 @@ build-clang:
       ppc-softmmu s390x-softmmu arm-linux-user
     MAKE_CHECK_ARGS: check
 
-build-fuzzer:
+build-oss-fuzz:
   <<: *native_build_job_definition
   variables:
     IMAGE: fedora
   script:
-    - mkdir build
-    - cd build
-    - ../configure --cc=clang --cxx=clang++ --enable-fuzzing
-                   --enable-sanitizers --target-list=x86_64-softmmu
-    - make -j"$JOBS" all check-build x86_64-softmmu/fuzz
-    - make check
-    - for fuzzer in i440fx-qos-fork-fuzz i440fx-qos-noreset-fuzz
-        i440fx-qtest-reboot-fuzz virtio-scsi-flags-fuzz virtio-scsi-fuzz ; do
-          echo Testing ${fuzzer} ... ;
-          x86_64-softmmu/qemu-fuzz-x86_64 --fuzz-target=${fuzzer} -runs=1000
-            || exit 1 ;
+    - mkdir build-oss-fuzz
+    - CC="clang" CXX="clang++" CFLAGS="-fsanitize=address"
+      ./scripts/oss-fuzz/build.sh
+    - for fuzzer in $(find ./build-oss-fuzz/DEST_DIR/ -executable -type f
+                      | grep -v slirp); do
+        grep "LLVMFuzzerTestOneInput" ${fuzzer} > /dev/null 2>&1 || continue ;
+        echo Testing ${fuzzer} ... ;
+        ASAN_OPTIONS="fast_unwind_on_malloc=0"
+         "${fuzzer}" -runs=1000 -seed=1 || exit 1 ;
       done
 
 build-tci:

MAINTAINERS

@@ -2449,9 +2449,11 @@ M: Alexander Bulekov <alxndr@bu.edu>
 R: Paolo Bonzini <pbonzini@redhat.com>
 R: Bandan Das <bsd@redhat.com>
 R: Stefan Hajnoczi <stefanha@redhat.com>
+R: Thomas Huth <thuth@redhat.com>
 S: Maintained
 F: tests/qtest/fuzz/
 F: scripts/oss-fuzz/
+F: docs/devel/fuzzing.txt
 
 Register API
 M: Alistair Francis <alistair@alistair23.me>

configure

@@ -6337,7 +6337,7 @@ fi
 # checks for fuzzer
 if test "$fuzzing" = "yes" ; then
   write_c_fuzzer_skeleton
-  if compile_prog "$CPU_CFLAGS -Werror -fsanitize=address,fuzzer" ""; then
+  if compile_prog "$CPU_CFLAGS -Werror -fsanitize=fuzzer" ""; then
       have_fuzzer=yes
   fi
 fi
@@ -7893,11 +7893,11 @@ if test "$have_mlockall" = "yes" ; then
 fi
 if test "$fuzzing" = "yes" ; then
   if test "$have_fuzzer" = "yes"; then
-    FUZZ_LDFLAGS=" -fsanitize=address,fuzzer"
-    FUZZ_CFLAGS=" -fsanitize=address,fuzzer"
-    CFLAGS="$CFLAGS -fsanitize=address,fuzzer-no-link"
+    FUZZ_LDFLAGS=" -fsanitize=fuzzer"
+    FUZZ_CFLAGS=" -fsanitize=fuzzer"
+    CFLAGS="$CFLAGS -fsanitize=fuzzer-no-link"
   else
-    error_exit "Your compiler doesn't support -fsanitize=address,fuzzer"
+    error_exit "Your compiler doesn't support -fsanitize=fuzzer"
     exit 1
   fi
 fi

docs/devel/fuzzing.txt

@@ -23,9 +23,12 @@ AddressSanitizer mmaps ~20TB of memory, as part of its detection. This results
 in a large page-map, and a much slower fork().
 
 To build the fuzzers, install a recent version of clang:
-Configure with (substitute the clang binaries with the version you installed):
+Configure with (substitute the clang binaries with the version you installed).
+Here, enable-sanitizers, is optional but it allows us to reliably detect bugs
+such as out-of-bounds accesses, use-after-frees, double-frees etc.
 
-    CC=clang-8 CXX=clang++-8 /path/to/configure --enable-fuzzing
+    CC=clang-8 CXX=clang++-8 /path/to/configure --enable-fuzzing \
+                                                --enable-sanitizers
 
 Fuzz targets are built similarly to system/softmmu:
 
@@ -45,6 +48,62 @@ Information about these is available by passing -help=1
 Now the only thing left to do is wait for the fuzzer to trigger potential
 crashes.
 
+== Useful libFuzzer flags ==
+
+As mentioned above, libFuzzer accepts some arguments. Passing -help=1 will list
+the available arguments. In particular, these arguments might be helpful:
+
+$CORPUS_DIR/ : Specify a directory as the last argument to libFuzzer. libFuzzer
+stores each "interesting" input in this corpus directory. The next time you run
+libFuzzer, it will read all of the inputs from the corpus, and continue fuzzing
+from there. You can also specify multiple directories. libFuzzer loads existing
+inputs from all specified directories, but will only write new ones to the
+first one specified.
+
+-max_len=4096 : specify the maximum byte-length of the inputs libFuzzer will
+generate.
+
+-close_fd_mask={1,2,3} : close, stderr, or both. Useful for targets that
+trigger many debug/error messages, or create output on the serial console.
+
+-jobs=4 -workers=4 : These arguments configure libFuzzer to run 4 fuzzers in
+parallel (4 fuzzing jobs in 4 worker processes). Alternatively, with only
+-jobs=N, libFuzzer automatically spawns a number of workers less than or equal
+to half the available CPU cores. Replace 4 with a number appropriate for your
+machine. Make sure to specify a $CORPUS_DIR, which will allow the parallel
+fuzzers to share information about the interesting inputs they find.
+
+-use_value_profile=1 : For each comparison operation, libFuzzer computes 
+(caller_pc&4095) | (popcnt(Arg1 ^ Arg2) << 12) and places this in the coverage
+table. Useful for targets with "magic" constants. If Arg1 came from the fuzzer's
+input and Arg2 is a magic constant, then each time the Hamming distance
+between Arg1 and Arg2 decreases, libFuzzer adds the input to the corpus.
+
+-shrink=1 : Tries to make elements of the corpus "smaller". Might lead to
+better coverage performance, depending on the target.
+
+Note that libFuzzer's exact behavior will depend on the version of
+clang and libFuzzer used to build the device fuzzers.
+
+== Generating Coverage Reports ==
+Code coverage is a crucial metric for evaluating a fuzzer's performance.
+libFuzzer's output provides a "cov: " column that provides a total number of
+unique blocks/edges covered. To examine coverage on a line-by-line basis we
+can use Clang coverage:
+
+ 1. Configure libFuzzer to store a corpus of all interesting inputs (see
+    CORPUS_DIR above)
+ 2. ./configure the QEMU build with:
+    --enable-fuzzing \
+    --extra-cflags="-fprofile-instr-generate -fcoverage-mapping"
+ 3. Re-run the fuzzer. Specify $CORPUS_DIR/* as an argument, telling libfuzzer
+    to execute all of the inputs in $CORPUS_DIR and exit. Once the process
+    exits, you should find a file, "default.profraw" in the working directory.
+ 4. Execute these commands to generate a detailed HTML coverage-report:
+ llvm-profdata merge -output=default.profdata default.profraw
+ llvm-cov show ./path/to/qemu-fuzz-i386 -instr-profile=default.profdata \
+ --format html -output-dir=/path/to/output/report
+
 == Adding a new fuzzer ==
 Coverage over virtual devices can be improved by adding additional fuzzers.
 Fuzzers are kept in tests/qtest/fuzz/ and should be added to

hw/arm/allwinner-h3.c

@@ -358,6 +358,7 @@ static void allwinner_h3_realize(DeviceState *dev, Error **errp)
                               "sd-bus");
 
     /* EMAC */
+    /* FIXME use qdev NIC properties instead of nd_table[] */
     if (nd_table[0].used) {
         qemu_check_nic_model(&nd_table[0], TYPE_AW_SUN8I_EMAC);
         qdev_set_nic_properties(DEVICE(&s->emac), &nd_table[0]);

hw/arm/msf2-soc.c

@@ -82,10 +82,6 @@ static void m2sxxx_soc_initfn(Object *obj)
     }
 
     object_initialize_child(obj, "emac", &s->emac, TYPE_MSS_EMAC);
-    if (nd_table[0].used) {
-        qemu_check_nic_model(&nd_table[0], TYPE_MSS_EMAC);
-        qdev_set_nic_properties(DEVICE(&s->emac), &nd_table[0]);
-    }
 }
 
 static void m2sxxx_soc_realize(DeviceState *dev_soc, Error **errp)
@@ -187,6 +183,11 @@ static void m2sxxx_soc_realize(DeviceState *dev_soc, Error **errp)
         g_free(bus_name);
     }
 
+    /* FIXME use qdev NIC properties instead of nd_table[] */
+    if (nd_table[0].used) {
+        qemu_check_nic_model(&nd_table[0], TYPE_MSS_EMAC);
+        qdev_set_nic_properties(DEVICE(&s->emac), &nd_table[0]);
+    }
     dev = DEVICE(&s->emac);
     object_property_set_link(OBJECT(&s->emac), "ahb-bus",
                              OBJECT(get_system_memory()), &error_abort);

hw/arm/xlnx-versal.c

@@ -160,6 +160,7 @@ static void versal_create_gems(Versal *s, qemu_irq *pic)
         object_initialize_child(OBJECT(s), name, &s->lpd.iou.gem[i],
                                 TYPE_CADENCE_GEM);
         dev = DEVICE(&s->lpd.iou.gem[i]);
+        /* FIXME use qdev NIC properties instead of nd_table[] */
         if (nd->used) {
             qemu_check_nic_model(nd, "cadence_gem");
             qdev_set_nic_properties(dev, nd);

hw/arm/xlnx-zynqmp.c

@@ -455,6 +455,7 @@ static void xlnx_zynqmp_realize(DeviceState *dev, Error **errp)
     for (i = 0; i < XLNX_ZYNQMP_NUM_GEMS; i++) {
         NICInfo *nd = &nd_table[i];
 
+        /* FIXME use qdev NIC properties instead of nd_table[] */
         if (nd->used) {
             qemu_check_nic_model(nd, TYPE_CADENCE_GEM);
             qdev_set_nic_properties(DEVICE(&s->gem[i]), nd);

hw/dma/sparc32_dma.c

@@ -341,6 +341,7 @@ static void sparc32_ledma_device_realize(DeviceState *dev, Error **errp)
     DeviceState *d;
     NICInfo *nd = &nd_table[0];
 
+    /* FIXME use qdev NIC properties instead of nd_table[] */
     qemu_check_nic_model(nd, TYPE_LANCE);
 
     d = qdev_new(TYPE_LANCE);

hw/riscv/sifive_u.c

@@ -714,6 +714,7 @@ static void sifive_u_soc_realize(DeviceState *dev, Error **errp)
     }
     sysbus_mmio_map(SYS_BUS_DEVICE(&s->otp), 0, memmap[SIFIVE_U_OTP].base);
 
+    /* FIXME use qdev NIC properties instead of nd_table[] */
     if (nd->used) {
         qemu_check_nic_model(nd, TYPE_CADENCE_GEM);
         qdev_set_nic_properties(DEVICE(&s->gem), nd);

scripts/oss-fuzz/build.sh

@@ -68,7 +68,7 @@ mkdir -p "$DEST_DIR/lib/"  # Copy the shared libraries here
 
 # Build once to get the list of dynamic lib paths, and copy them over
 ../configure --disable-werror --cc="$CC" --cxx="$CXX" \
-    --extra-cflags="$EXTRA_CFLAGS"
+    --extra-cflags="$EXTRA_CFLAGS" --target-list="i386-softmmu"
 
 if ! make CONFIG_FUZZ=y CFLAGS="$LIB_FUZZING_ENGINE" "-j$(nproc)" \
     i386-softmmu/fuzz; then

tests/qtest/fuzz/fuzz.c

@@ -143,7 +143,7 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
 {
 
     char *target_name;
-    char *dir;
+    char *bindir, *datadir;
     bool serialize = false;
 
     /* Initialize qgraph and modules */
@@ -164,11 +164,13 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
          * location of the executable. Using this we add exec_dir/pc-bios to
          * the datadirs.
          */
-        dir = g_build_filename(g_path_get_dirname(**argv), "pc-bios", NULL);
-        if (g_file_test(dir, G_FILE_TEST_IS_DIR)) {
-            qemu_add_data_dir(dir);
+        bindir = g_path_get_dirname(**argv);
+        datadir = g_build_filename(bindir, "pc-bios", NULL);
+        g_free(bindir);
+        if (g_file_test(datadir, G_FILE_TEST_IS_DIR)) {
+            qemu_add_data_dir(datadir);
         }
-        g_free(dir);
+        g_free(datadir);
     } else if (*argc > 1) {  /* The target is specified as an argument */
         target_name = (*argv)[1];
         if (!strstr(target_name, "--fuzz-target=")) {