[PULL 0/7] 2021-01-20 fuzzing patches

[PULL 0/7] 2021-01-20 fuzzing patches

[Alexander Bulekov]

Hi Peter,

The following changes since commit 48202c712412c803ddb56365c7bca322aa4e7506:

  Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210119-1' into staging (2021-01-19 15:47:23 +0000)

are available in the Git repository at:

  https://gitlab.com/a1xndr/qemu.git tags/pull-request-2021-01-20

for you to fetch changes up to fae446ae7b6f746377186b3e19fd3f732a8b4325:

  fuzz: add virtio-9p configurations for fuzzing (2021-01-20 12:30:26 -0500)

----------------------------------------------------------------
* Add fuzzer configs for virtio-9p
* Add fuzzer configs for PATA/SATA ide-hd and atapi devices
* Remove a DMA callback check that was limitting the fuzzer
* Improve debug info and documentation

----------------------------------------------------------------
Alexander Bulekov (7):
      fuzz: ignore address_space_map is_write flag
      fuzz: refine the ide/ahci fuzzer configs
      docs/fuzz: fix pre-meson path
      fuzz: log the arguments used to initialize QEMU
      fuzz: enable dynamic args for generic-fuzz configs
      docs/fuzz: add some information about OSS-Fuzz
      fuzz: add virtio-9p configurations for fuzzing

 docs/devel/fuzzing.rst                  | 31 ++++++++++++++++++++++++++++---
 include/exec/memory.h                   |  8 +++-----
 include/exec/memory_ldst_cached.h.inc   |  6 +++---
 memory_ldst.c.inc                       |  8 ++++----
 softmmu/memory.c                        |  5 ++---
 softmmu/physmem.c                       |  4 ++--
 tests/qtest/fuzz/fuzz.c                 | 11 ++++++++++-
 tests/qtest/fuzz/generic_fuzz.c         | 19 ++++++++++++-------
 tests/qtest/fuzz/generic_fuzz_configs.h | 41 ++++++++++++++++++++++++++++++++++++++++-
 9 files changed, 104 insertions(+), 29 deletions(-)

Alexander Bulekov (7):
  fuzz: ignore address_space_map is_write flag
  fuzz: refine the ide/ahci fuzzer configs
  docs/fuzz: fix pre-meson path
  fuzz: log the arguments used to initialize QEMU
  fuzz: enable dynamic args for generic-fuzz configs
  docs/fuzz: add some information about OSS-Fuzz
  fuzz: add virtio-9p configurations for fuzzing

 docs/devel/fuzzing.rst                  | 31 +++++++++++++++++--
 include/exec/memory.h                   |  8 ++---
 include/exec/memory_ldst_cached.h.inc   |  6 ++--
 memory_ldst.c.inc                       |  8 ++---
 softmmu/memory.c                        |  5 ++-
 softmmu/physmem.c                       |  4 +--
 tests/qtest/fuzz/fuzz.c                 | 11 ++++++-
 tests/qtest/fuzz/generic_fuzz.c         | 19 +++++++-----
 tests/qtest/fuzz/generic_fuzz_configs.h | 41 ++++++++++++++++++++++++-
 9 files changed, 104 insertions(+), 29 deletions(-)

-- 
2.28.0

[PULL 1/7] fuzz: ignore address_space_map is_write flag

[Alexander Bulekov]

We passed an is_write flag to the fuzz_dma_read_cb function to
differentiate between the mapped DMA regions that need to be populated
with fuzzed data, and those that don't. We simply passed through the
address_space_map is_write parameter. The goal was to cut down on
unnecessarily populating mapped DMA regions, when they are not read
from.

Unfortunately, nothing precludes code from reading from regions mapped
with is_write=true. For example, see:
https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04729.html

This patch removes the is_write parameter to fuzz_dma_read_cb. As a
result, we will fill all mapped DMA regions with fuzzed data, ignoring
the specified transfer direction.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
 include/exec/memory.h                 | 8 +++-----
 include/exec/memory_ldst_cached.h.inc | 6 +++---
 memory_ldst.c.inc                     | 8 ++++----
 softmmu/memory.c                      | 5 ++---
 softmmu/physmem.c                     | 4 ++--
 tests/qtest/fuzz/generic_fuzz.c       | 9 +++------
 6 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 521d9901d7..0f89787de2 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -45,13 +45,11 @@ DECLARE_OBJ_CHECKERS(IOMMUMemoryRegion, IOMMUMemoryRegionClass,
 #ifdef CONFIG_FUZZ
 void fuzz_dma_read_cb(size_t addr,
                       size_t len,
-                      MemoryRegion *mr,
-                      bool is_write);
+                      MemoryRegion *mr);
 #else
 static inline void fuzz_dma_read_cb(size_t addr,
                                     size_t len,
-                                    MemoryRegion *mr,
-                                    bool is_write)
+                                    MemoryRegion *mr)
 {
     /* Do Nothing */
 }
@@ -2504,7 +2502,7 @@ address_space_read_cached(MemoryRegionCache *cache, hwaddr addr,
                           void *buf, hwaddr len)
 {
     assert(addr < cache->len && len <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr);
     if (likely(cache->ptr)) {
         memcpy(buf, cache->ptr + addr, len);
         return MEMTX_OK;
diff --git a/include/exec/memory_ldst_cached.h.inc b/include/exec/memory_ldst_cached.h.inc
index 01efad62de..7bc8790d34 100644
--- a/include/exec/memory_ldst_cached.h.inc
+++ b/include/exec/memory_ldst_cached.h.inc
@@ -28,7 +28,7 @@ static inline uint32_t ADDRESS_SPACE_LD_CACHED(l)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 4 <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, 4, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, 4, cache->mrs.mr);
     if (likely(cache->ptr)) {
         return LD_P(l)(cache->ptr + addr);
     } else {
@@ -40,7 +40,7 @@ static inline uint64_t ADDRESS_SPACE_LD_CACHED(q)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 8 <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, 8, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, 8, cache->mrs.mr);
     if (likely(cache->ptr)) {
         return LD_P(q)(cache->ptr + addr);
     } else {
@@ -52,7 +52,7 @@ static inline uint32_t ADDRESS_SPACE_LD_CACHED(uw)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 2 <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, 2, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, 2, cache->mrs.mr);
     if (likely(cache->ptr)) {
         return LD_P(uw)(cache->ptr + addr);
     } else {
diff --git a/memory_ldst.c.inc b/memory_ldst.c.inc
index 2fed2de18e..b56e961967 100644
--- a/memory_ldst.c.inc
+++ b/memory_ldst.c.inc
@@ -42,7 +42,7 @@ static inline uint32_t glue(address_space_ldl_internal, SUFFIX)(ARG1_DECL,
                                         MO_32 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 4, mr, false);
+        fuzz_dma_read_cb(addr, 4, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
@@ -111,7 +111,7 @@ static inline uint64_t glue(address_space_ldq_internal, SUFFIX)(ARG1_DECL,
                                         MO_64 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 8, mr, false);
+        fuzz_dma_read_cb(addr, 8, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
@@ -177,7 +177,7 @@ uint32_t glue(address_space_ldub, SUFFIX)(ARG1_DECL,
         r = memory_region_dispatch_read(mr, addr1, &val, MO_8, attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 1, mr, false);
+        fuzz_dma_read_cb(addr, 1, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         val = ldub_p(ptr);
         r = MEMTX_OK;
@@ -215,7 +215,7 @@ static inline uint32_t glue(address_space_lduw_internal, SUFFIX)(ARG1_DECL,
                                         MO_16 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 2, mr, false);
+        fuzz_dma_read_cb(addr, 2, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 333e1ed7b0..4fc0071dcd 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1440,7 +1440,7 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
     unsigned size = memop_size(op);
     MemTxResult r;
 
-    fuzz_dma_read_cb(addr, size, mr, false);
+    fuzz_dma_read_cb(addr, size, mr);
     if (!memory_region_access_valid(mr, addr, size, false, attrs)) {
         *pval = unassigned_mem_read(mr, addr, size);
         return MEMTX_DECODE_ERROR;
@@ -3282,8 +3282,7 @@ void memory_region_init_rom_device(MemoryRegion *mr,
 #ifdef CONFIG_FUZZ
 void __attribute__((weak)) fuzz_dma_read_cb(size_t addr,
                       size_t len,
-                      MemoryRegion *mr,
-                      bool is_write)
+                      MemoryRegion *mr)
 {
 }
 #endif
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 6301f4f0a5..5aaec2f2c1 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2824,7 +2824,7 @@ MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
             stn_he_p(buf, l, val);
         } else {
             /* RAM case */
-            fuzz_dma_read_cb(addr, len, mr, false);
+            fuzz_dma_read_cb(addr, len, mr);
             ram_ptr = qemu_ram_ptr_length(mr->ram_block, addr1, &l, false);
             memcpy(buf, ram_ptr, l);
         }
@@ -3185,7 +3185,7 @@ void *address_space_map(AddressSpace *as,
     memory_region_ref(mr);
     *plen = flatview_extend_translation(fv, addr, len, mr, xlat,
                                         l, is_write, attrs);
-    fuzz_dma_read_cb(addr, *plen, mr, is_write);
+    fuzz_dma_read_cb(addr, *plen, mr);
     ptr = qemu_ram_ptr_length(mr->ram_block, xlat, plen, true);
 
     return ptr;
diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index be76d47d2d..deb74f15be 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -175,7 +175,7 @@ static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
  * generic_fuzz(), avoiding potential race-conditions, which we don't have
  * a good way for reproducing right now.
  */
-void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
+void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr)
 {
     /* Are we in the generic-fuzzer or are we using another fuzz-target? */
     if (!qts_global) {
@@ -187,14 +187,11 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
      * - We have no DMA patterns defined
      * - The length of the DMA read request is zero
      * - The DMA read is hitting an MR other than the machine's main RAM
-     * - The DMA request is not a read (what happens for a address_space_map
-     *   with is_write=True? Can the device use the same pointer to do reads?)
      * - The DMA request hits past the bounds of our RAM
      */
     if (dma_patterns->len == 0
         || len == 0
         || mr != current_machine->ram
-        || is_write
         || addr > current_machine->ram_size) {
         return;
     }
@@ -213,12 +210,12 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
             double_fetch = true;
             if (addr < region.addr
                 && avoid_double_fetches) {
-                fuzz_dma_read_cb(addr, region.addr - addr, mr, is_write);
+                fuzz_dma_read_cb(addr, region.addr - addr, mr);
             }
             if (addr + len > region.addr + region.size
                 && avoid_double_fetches) {
                 fuzz_dma_read_cb(region.addr + region.size,
-                        addr + len - (region.addr + region.size), mr, is_write);
+                        addr + len - (region.addr + region.size), mr);
             }
             return;
         }
-- 
2.28.0

[PULL 2/7] fuzz: refine the ide/ahci fuzzer configs

[Alexander Bulekov]

Disks work differently depending on the x86 machine type (SATA vs PATA).
Additionally, we should fuzz the atapi code paths, which might contain
vulnerabilities such as CVE-2020-29443. This patch adds hard-disk and
cdrom generic-fuzzer configs for both the pc (PATA) and q35 (SATA)
machine types.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
---
 tests/qtest/fuzz/generic_fuzz_configs.h | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/tests/qtest/fuzz/generic_fuzz_configs.h b/tests/qtest/fuzz/generic_fuzz_configs.h
index 7fed035345..aa4c03f1ae 100644
--- a/tests/qtest/fuzz/generic_fuzz_configs.h
+++ b/tests/qtest/fuzz/generic_fuzz_configs.h
@@ -85,10 +85,28 @@ const generic_fuzz_config predefined_configs[] = {
         .objects = "intel-hda",
     },{
         .name = "ide-hd",
+        .args = "-machine pc -nodefaults "
+        "-drive file=null-co://,if=none,format=raw,id=disk0 "
+        "-device ide-hd,drive=disk0",
+        .objects = "*ide*",
+    },{
+        .name = "ide-atapi",
+        .args = "-machine pc -nodefaults "
+        "-drive file=null-co://,if=none,format=raw,id=disk0 "
+        "-device ide-cd,drive=disk0",
+        .objects = "*ide*",
+    },{
+        .name = "ahci-hd",
         .args = "-machine q35 -nodefaults "
         "-drive file=null-co://,if=none,format=raw,id=disk0 "
         "-device ide-hd,drive=disk0",
-        .objects = "ahci*",
+        .objects = "*ahci*",
+    },{
+        .name = "ahci-atapi",
+        .args = "-machine q35 -nodefaults "
+        "-drive file=null-co://,if=none,format=raw,id=disk0 "
+        "-device ide-cd,drive=disk0",
+        .objects = "*ahci*",
     },{
         .name = "floppy",
         .args = "-machine pc -nodefaults -device floppy,id=floppy0 "
-- 
2.28.0

[PULL 3/7] docs/fuzz: fix pre-meson path

[Alexander Bulekov]

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 docs/devel/fuzzing.rst | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/docs/devel/fuzzing.rst b/docs/devel/fuzzing.rst
index 6096242d99..5f5200c843 100644
--- a/docs/devel/fuzzing.rst
+++ b/docs/devel/fuzzing.rst
@@ -119,7 +119,7 @@ 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
-``tests/qtest/fuzz/Makefile.include``
+``tests/qtest/fuzz/meson.build``
 
 Fuzzers can rely on both qtest and libqos to communicate with virtual devices.
 
@@ -128,8 +128,7 @@ Fuzzers can rely on both qtest and libqos to communicate with virtual devices.
 2. Write the fuzzing code using the libqtest/libqos API. See existing fuzzers
    for reference.
 
-3. Register the fuzzer in ``tests/fuzz/Makefile.include`` by appending the
-   corresponding object to fuzz-obj-y
+3. Add the fuzzer to ``tests/qtest/fuzz/meson.build``.
 
 Fuzzers can be more-or-less thought of as special qtest programs which can
 modify the qtest commands and/or qtest command arguments based on inputs
-- 
2.28.0

[PULL 4/7] fuzz: log the arguments used to initialize QEMU

[Alexander Bulekov]

This is useful for building reproducers. Instead checking the code or
the QEMU_FUZZ_ARGS, the arguments are at the top of the crash log.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 tests/qtest/fuzz/fuzz.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tests/qtest/fuzz/fuzz.c b/tests/qtest/fuzz/fuzz.c
index 238866a037..496d11a231 100644
--- a/tests/qtest/fuzz/fuzz.c
+++ b/tests/qtest/fuzz/fuzz.c
@@ -159,6 +159,8 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
     char *target_name;
     const char *bindir;
     char *datadir;
+    GString *cmd_line;
+    gchar *pretty_cmd_line;
     bool serialize = false;
 
     /* Initialize qgraph and modules */
@@ -217,7 +219,7 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
     }
 
     /* Run QEMU's softmmu main with the fuzz-target dependent arguments */
-    GString *cmd_line = fuzz_target->get_init_cmdline(fuzz_target);
+    cmd_line = fuzz_target->get_init_cmdline(fuzz_target);
     g_string_append_printf(cmd_line, " %s -qtest /dev/null ",
                            getenv("QTEST_LOG") ? "" : "-qtest-log none");
 
@@ -226,6 +228,13 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
     wordexp(cmd_line->str, &result, 0);
     g_string_free(cmd_line, true);
 
+    if (getenv("QTEST_LOG")) {
+        pretty_cmd_line  = g_strjoinv(" ", result.we_wordv + 1);
+        printf("Starting %s with Arguments: %s\n",
+                result.we_wordv[0], pretty_cmd_line);
+        g_free(pretty_cmd_line);
+    }
+
     qemu_init(result.we_wordc, result.we_wordv, NULL);
 
     /* re-enable the rcu atfork, which was previously disabled in qemu_init */
-- 
2.28.0

[PULL 5/7] fuzz: enable dynamic args for generic-fuzz configs

[Alexander Bulekov]

For some device configurations, it is useful to configure some
resources, and adjust QEMU arguments at runtime, prior to fuzzing. This
patch adds an "argfunc" to generic the generic_fuzz_config. When
specified, it is responsible for configuring the resources and returning
a string containing the corresponding QEMU arguments. This can be useful
for targets that rely on e.g.:
 * a temporary qcow2 image
 * a temporary directory
 * an unused TCP port used to bind the VNC server

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 tests/qtest/fuzz/generic_fuzz.c         | 10 +++++++++-
 tests/qtest/fuzz/generic_fuzz_configs.h |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index deb74f15be..ee8c17a04c 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -933,12 +933,20 @@ static GString *generic_fuzz_cmdline(FuzzTarget *t)
 
 static GString *generic_fuzz_predefined_config_cmdline(FuzzTarget *t)
 {
+    gchar *args;
     const generic_fuzz_config *config;
     g_assert(t->opaque);
 
     config = t->opaque;
     setenv("QEMU_AVOID_DOUBLE_FETCH", "1", 1);
-    setenv("QEMU_FUZZ_ARGS", config->args, 1);
+    if (config->argfunc) {
+        args = config->argfunc();
+        setenv("QEMU_FUZZ_ARGS", args, 1);
+        g_free(args);
+    } else {
+        g_assert_nonnull(config->args);
+        setenv("QEMU_FUZZ_ARGS", config->args, 1);
+    }
     setenv("QEMU_FUZZ_OBJECTS", config->objects, 1);
     return generic_fuzz_cmdline(t);
 }
diff --git a/tests/qtest/fuzz/generic_fuzz_configs.h b/tests/qtest/fuzz/generic_fuzz_configs.h
index aa4c03f1ae..51e69c6e42 100644
--- a/tests/qtest/fuzz/generic_fuzz_configs.h
+++ b/tests/qtest/fuzz/generic_fuzz_configs.h
@@ -16,6 +16,7 @@
 
 typedef struct generic_fuzz_config {
     const char *name, *args, *objects;
+    gchar* (*argfunc)(void); /* Result must be freeable by g_free() */
 } generic_fuzz_config;
 
 const generic_fuzz_config predefined_configs[] = {
-- 
2.28.0

[PULL 6/7] docs/fuzz: add some information about OSS-Fuzz

[Alexander Bulekov]

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
---
 docs/devel/fuzzing.rst | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/docs/devel/fuzzing.rst b/docs/devel/fuzzing.rst
index 5f5200c843..b9bb07988b 100644
--- a/docs/devel/fuzzing.rst
+++ b/docs/devel/fuzzing.rst
@@ -180,6 +180,32 @@ To ensure that these env variables have been configured correctly, we can use::
 
 The output should contain a complete list of matched MemoryRegions.
 
+OSS-Fuzz
+--------
+QEMU is continuously fuzzed on `OSS-Fuzz` __(https://github.com/google/oss-fuzz).
+By default, the OSS-Fuzz build will try to fuzz every fuzz-target. Since the
+generic-fuzz target requires additional information provided in environment
+variables, we pre-define some generic-fuzz configs in
+``tests/qtest/fuzz/generic_fuzz_configs.h``. Each config must specify:
+ * ``.name``: To identify the fuzzer config
+ * ``.args`` OR ``.argfunc``: A string or pointer to a function returning a
+   string.  These strings are used to specify the ``QEMU_FUZZ_ARGS``
+   environment variable.  ``argfunc`` is useful when the config relies on e.g.
+   a dynamically created temp directory, or a free tcp/udp port.
+ * ``.objects``: A string that specifies the ``QEMU_FUZZ_OBJECTS`` environment
+   variable.
+
+To fuzz additional devices/device configuration on OSS-Fuzz:
+ * Send patches for a new device-specific fuzzer
+ * Send patches for a new generic-fuzz config
+
+Build details:
+ * `The basic Dockerfile that sets up the environment for building QEMU's
+   fuzzers on OSS-Fuzz
+   <https://github.com/google/oss-fuzz/blob/master/projects/qemu/Dockerfile>`_
+ * The script responsible for building the fuzzers:
+   ``scripts/oss-fuzz/build.sh``
+
 Implementation Details / Fuzzer Lifecycle
 -----------------------------------------
 
-- 
2.28.0

[PULL 7/7] fuzz: add virtio-9p configurations for fuzzing

[Alexander Bulekov]

virtio-9p devices are often used to expose a virtual-filesystem to the
guest. There have been some bugs reported in this device, such as
CVE-2018-19364, and CVE-2021-20181. We should fuzz this device

This patch adds two virtio-9p configurations:
 * One with the widely used -fsdev local driver. This driver leaks some
   state in the form of files/directories created in the shared dir.
 * One with the synth driver. While it is not used in the real world, this
   driver won't leak leak state between fuzz inputs.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
---
 tests/qtest/fuzz/generic_fuzz_configs.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/qtest/fuzz/generic_fuzz_configs.h b/tests/qtest/fuzz/generic_fuzz_configs.h
index 51e69c6e42..5d599765c4 100644
--- a/tests/qtest/fuzz/generic_fuzz_configs.h
+++ b/tests/qtest/fuzz/generic_fuzz_configs.h
@@ -19,6 +19,16 @@ typedef struct generic_fuzz_config {
     gchar* (*argfunc)(void); /* Result must be freeable by g_free() */
 } generic_fuzz_config;
 
+static inline gchar *generic_fuzzer_virtio_9p_args(void){
+    char tmpdir[] = "/tmp/qemu-fuzz.XXXXXX";
+    g_assert_nonnull(mkdtemp(tmpdir));
+
+    return g_strdup_printf("-machine q35 -nodefaults "
+    "-device virtio-9p,fsdev=hshare,mount_tag=hshare "
+    "-fsdev local,id=hshare,path=%s,security_model=mapped-xattr,"
+    "writeout=immediate,fmode=0600,dmode=0700", tmpdir);
+}
+
 const generic_fuzz_config predefined_configs[] = {
     {
         .name = "virtio-net-pci-slirp",
@@ -60,6 +70,16 @@ const generic_fuzz_config predefined_configs[] = {
         .name = "virtio-mouse",
         .args = "-machine q35 -nodefaults -device virtio-mouse",
         .objects = "virtio*",
+    },{
+        .name = "virtio-9p",
+        .argfunc = generic_fuzzer_virtio_9p_args,
+        .objects = "virtio*",
+    },{
+        .name = "virtio-9p-synth",
+        .args = "-machine q35 -nodefaults "
+        "-device virtio-9p,fsdev=hshare,mount_tag=hshare "
+        "-fsdev synth,id=hshare",
+        .objects = "virtio*",
     },{
         .name = "e1000",
         .args = "-M q35 -nodefaults "
-- 
2.28.0

Re: [PULL 0/7] 2021-01-20 fuzzing patches

[Peter Maydell]

On Wed, 20 Jan 2021 at 17:45, Alexander Bulekov <alxndr@bu.edu> wrote:
>
> Hi Peter,
>
> The following changes since commit 48202c712412c803ddb56365c7bca322aa4e7506:
>
>   Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210119-1' into staging (2021-01-19 15:47:23 +0000)
>
> are available in the Git repository at:
>
>   https://gitlab.com/a1xndr/qemu.git tags/pull-request-2021-01-20
>
> for you to fetch changes up to fae446ae7b6f746377186b3e19fd3f732a8b4325:
>
>   fuzz: add virtio-9p configurations for fuzzing (2021-01-20 12:30:26 -0500)

Hi; some of these commits seem to be missing Reviewed-by: tags;
for instance "ignore address_space_map is_write flag" got a
Reviewed-by from Darren Kenny, and that tag is visible in the
(second) copy of the email for the pullreq that you sent to the
list, but it isn't in the commit that's at the tag you name above,
and it's the commits in the git repo that end up in master, not
the patch emails sent to the list.

Also, are you in a position to get your GPG key signed by
anybody else? I appreciate that that's pretty tricky right
now given Covid, but if you have the opportunity at some point
that would be useful.

thanks
-- PMM

Re: [PULL 0/7] 2021-01-20 fuzzing patches

[Alexander Bulekov]

On 210122 1506, Peter Maydell wrote:
> On Wed, 20 Jan 2021 at 17:45, Alexander Bulekov <alxndr@bu.edu> wrote:
> >
> > Hi Peter,
> >
> > The following changes since commit 48202c712412c803ddb56365c7bca322aa4e7506:
> >
> >   Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210119-1' into staging (2021-01-19 15:47:23 +0000)
> >
> > are available in the Git repository at:
> >
> >   https://gitlab.com/a1xndr/qemu.git tags/pull-request-2021-01-20
> >
> > for you to fetch changes up to fae446ae7b6f746377186b3e19fd3f732a8b4325:
> >
> >   fuzz: add virtio-9p configurations for fuzzing (2021-01-20 12:30:26 -0500)
> 
> Hi; some of these commits seem to be missing Reviewed-by: tags;
> for instance "ignore address_space_map is_write flag" got a
> Reviewed-by from Darren Kenny, and that tag is visible in the
> (second) copy of the email for the pullreq that you sent to the
> list, but it isn't in the commit that's at the tag you name above,
> and it's the commits in the git repo that end up in master, not
> the patch emails sent to the list.
> 
> Also, are you in a position to get your GPG key signed by
> anybody else? I appreciate that that's pretty tricky right
> now given Covid, but if you have the opportunity at some point
> that would be useful.
> 

Hi Peter,
Thank you for these pointers. I resent a PR with fixed tags. I should
also now have a few signatures on my key. I realized that Paolo asked me
to send the PR to him, so I fixed that in my RESEND.
Thanks again
-Alex

> thanks
> -- PMM

[PULL 0/7] 2021-01-20 fuzzing patches

[Alexander Bulekov]

Hi Peter,

The following changes since commit 48202c712412c803ddb56365c7bca322aa4e7506:

  Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210119-1' into staging (2021-01-19 15:47:23 +0000)

are available in the Git repository at:

  https://gitlab.com/a1xndr/qemu.git tags/pull-request-2021-01-20

for you to fetch changes up to fae446ae7b6f746377186b3e19fd3f732a8b4325:

  fuzz: add virtio-9p configurations for fuzzing (2021-01-20 12:30:26 -0500)

----------------------------------------------------------------
* Add fuzzer configs for virtio-9p
* Add fuzzer configs for PATA/SATA ide-hd and atapi devices
* Remove a DMA callback check that was limitting the fuzzer
* Improve debug info and documentation

----------------------------------------------------------------
Alexander Bulekov (7):
      fuzz: ignore address_space_map is_write flag
      fuzz: refine the ide/ahci fuzzer configs
      docs/fuzz: fix pre-meson path
      fuzz: log the arguments used to initialize QEMU
      fuzz: enable dynamic args for generic-fuzz configs
      docs/fuzz: add some information about OSS-Fuzz
      fuzz: add virtio-9p configurations for fuzzing

 docs/devel/fuzzing.rst                  | 31 ++++++++++++++++++++++++++++---
 include/exec/memory.h                   |  8 +++-----
 include/exec/memory_ldst_cached.h.inc   |  6 +++---
 memory_ldst.c.inc                       |  8 ++++----
 softmmu/memory.c                        |  5 ++---
 softmmu/physmem.c                       |  4 ++--
 tests/qtest/fuzz/fuzz.c                 | 11 ++++++++++-
 tests/qtest/fuzz/generic_fuzz.c         | 19 ++++++++++++-------
 tests/qtest/fuzz/generic_fuzz_configs.h | 41 ++++++++++++++++++++++++++++++++++++++++-
 9 files changed, 104 insertions(+), 29 deletions(-)

Alexander Bulekov (7):
  fuzz: ignore address_space_map is_write flag
  fuzz: refine the ide/ahci fuzzer configs
  docs/fuzz: fix pre-meson path
  fuzz: log the arguments used to initialize QEMU
  fuzz: enable dynamic args for generic-fuzz configs
  docs/fuzz: add some information about OSS-Fuzz
  fuzz: add virtio-9p configurations for fuzzing

 docs/devel/fuzzing.rst                  | 31 +++++++++++++++++--
 include/exec/memory.h                   |  8 ++---
 include/exec/memory_ldst_cached.h.inc   |  6 ++--
 memory_ldst.c.inc                       |  8 ++---
 softmmu/memory.c                        |  5 ++-
 softmmu/physmem.c                       |  4 +--
 tests/qtest/fuzz/fuzz.c                 | 11 ++++++-
 tests/qtest/fuzz/generic_fuzz.c         | 19 +++++++-----
 tests/qtest/fuzz/generic_fuzz_configs.h | 41 ++++++++++++++++++++++++-
 9 files changed, 104 insertions(+), 29 deletions(-)

-- 
2.28.0

[PULL 1/7] fuzz: ignore address_space_map is_write flag

[Alexander Bulekov]

We passed an is_write flag to the fuzz_dma_read_cb function to
differentiate between the mapped DMA regions that need to be populated
with fuzzed data, and those that don't. We simply passed through the
address_space_map is_write parameter. The goal was to cut down on
unnecessarily populating mapped DMA regions, when they are not read
from.

Unfortunately, nothing precludes code from reading from regions mapped
with is_write=true. For example, see:
https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04729.html

This patch removes the is_write parameter to fuzz_dma_read_cb. As a
result, we will fill all mapped DMA regions with fuzzed data, ignoring
the specified transfer direction.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
 include/exec/memory.h                 | 8 +++-----
 include/exec/memory_ldst_cached.h.inc | 6 +++---
 memory_ldst.c.inc                     | 8 ++++----
 softmmu/memory.c                      | 5 ++---
 softmmu/physmem.c                     | 4 ++--
 tests/qtest/fuzz/generic_fuzz.c       | 9 +++------
 6 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 521d9901d7..0f89787de2 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -45,13 +45,11 @@ DECLARE_OBJ_CHECKERS(IOMMUMemoryRegion, IOMMUMemoryRegionClass,
 #ifdef CONFIG_FUZZ
 void fuzz_dma_read_cb(size_t addr,
                       size_t len,
-                      MemoryRegion *mr,
-                      bool is_write);
+                      MemoryRegion *mr);
 #else
 static inline void fuzz_dma_read_cb(size_t addr,
                                     size_t len,
-                                    MemoryRegion *mr,
-                                    bool is_write)
+                                    MemoryRegion *mr)
 {
     /* Do Nothing */
 }
@@ -2504,7 +2502,7 @@ address_space_read_cached(MemoryRegionCache *cache, hwaddr addr,
                           void *buf, hwaddr len)
 {
     assert(addr < cache->len && len <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, len, cache->mrs.mr);
     if (likely(cache->ptr)) {
         memcpy(buf, cache->ptr + addr, len);
         return MEMTX_OK;
diff --git a/include/exec/memory_ldst_cached.h.inc b/include/exec/memory_ldst_cached.h.inc
index 01efad62de..7bc8790d34 100644
--- a/include/exec/memory_ldst_cached.h.inc
+++ b/include/exec/memory_ldst_cached.h.inc
@@ -28,7 +28,7 @@ static inline uint32_t ADDRESS_SPACE_LD_CACHED(l)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 4 <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, 4, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, 4, cache->mrs.mr);
     if (likely(cache->ptr)) {
         return LD_P(l)(cache->ptr + addr);
     } else {
@@ -40,7 +40,7 @@ static inline uint64_t ADDRESS_SPACE_LD_CACHED(q)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 8 <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, 8, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, 8, cache->mrs.mr);
     if (likely(cache->ptr)) {
         return LD_P(q)(cache->ptr + addr);
     } else {
@@ -52,7 +52,7 @@ static inline uint32_t ADDRESS_SPACE_LD_CACHED(uw)(MemoryRegionCache *cache,
     hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
 {
     assert(addr < cache->len && 2 <= cache->len - addr);
-    fuzz_dma_read_cb(cache->xlat + addr, 2, cache->mrs.mr, false);
+    fuzz_dma_read_cb(cache->xlat + addr, 2, cache->mrs.mr);
     if (likely(cache->ptr)) {
         return LD_P(uw)(cache->ptr + addr);
     } else {
diff --git a/memory_ldst.c.inc b/memory_ldst.c.inc
index 2fed2de18e..b56e961967 100644
--- a/memory_ldst.c.inc
+++ b/memory_ldst.c.inc
@@ -42,7 +42,7 @@ static inline uint32_t glue(address_space_ldl_internal, SUFFIX)(ARG1_DECL,
                                         MO_32 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 4, mr, false);
+        fuzz_dma_read_cb(addr, 4, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
@@ -111,7 +111,7 @@ static inline uint64_t glue(address_space_ldq_internal, SUFFIX)(ARG1_DECL,
                                         MO_64 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 8, mr, false);
+        fuzz_dma_read_cb(addr, 8, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
@@ -177,7 +177,7 @@ uint32_t glue(address_space_ldub, SUFFIX)(ARG1_DECL,
         r = memory_region_dispatch_read(mr, addr1, &val, MO_8, attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 1, mr, false);
+        fuzz_dma_read_cb(addr, 1, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         val = ldub_p(ptr);
         r = MEMTX_OK;
@@ -215,7 +215,7 @@ static inline uint32_t glue(address_space_lduw_internal, SUFFIX)(ARG1_DECL,
                                         MO_16 | devend_memop(endian), attrs);
     } else {
         /* RAM case */
-        fuzz_dma_read_cb(addr, 2, mr, false);
+        fuzz_dma_read_cb(addr, 2, mr);
         ptr = qemu_map_ram_ptr(mr->ram_block, addr1);
         switch (endian) {
         case DEVICE_LITTLE_ENDIAN:
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 333e1ed7b0..4fc0071dcd 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1440,7 +1440,7 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
     unsigned size = memop_size(op);
     MemTxResult r;
 
-    fuzz_dma_read_cb(addr, size, mr, false);
+    fuzz_dma_read_cb(addr, size, mr);
     if (!memory_region_access_valid(mr, addr, size, false, attrs)) {
         *pval = unassigned_mem_read(mr, addr, size);
         return MEMTX_DECODE_ERROR;
@@ -3282,8 +3282,7 @@ void memory_region_init_rom_device(MemoryRegion *mr,
 #ifdef CONFIG_FUZZ
 void __attribute__((weak)) fuzz_dma_read_cb(size_t addr,
                       size_t len,
-                      MemoryRegion *mr,
-                      bool is_write)
+                      MemoryRegion *mr)
 {
 }
 #endif
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 6301f4f0a5..5aaec2f2c1 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2824,7 +2824,7 @@ MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
             stn_he_p(buf, l, val);
         } else {
             /* RAM case */
-            fuzz_dma_read_cb(addr, len, mr, false);
+            fuzz_dma_read_cb(addr, len, mr);
             ram_ptr = qemu_ram_ptr_length(mr->ram_block, addr1, &l, false);
             memcpy(buf, ram_ptr, l);
         }
@@ -3185,7 +3185,7 @@ void *address_space_map(AddressSpace *as,
     memory_region_ref(mr);
     *plen = flatview_extend_translation(fv, addr, len, mr, xlat,
                                         l, is_write, attrs);
-    fuzz_dma_read_cb(addr, *plen, mr, is_write);
+    fuzz_dma_read_cb(addr, *plen, mr);
     ptr = qemu_ram_ptr_length(mr->ram_block, xlat, plen, true);
 
     return ptr;
diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index be76d47d2d..deb74f15be 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -175,7 +175,7 @@ static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
  * generic_fuzz(), avoiding potential race-conditions, which we don't have
  * a good way for reproducing right now.
  */
-void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
+void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr)
 {
     /* Are we in the generic-fuzzer or are we using another fuzz-target? */
     if (!qts_global) {
@@ -187,14 +187,11 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
      * - We have no DMA patterns defined
      * - The length of the DMA read request is zero
      * - The DMA read is hitting an MR other than the machine's main RAM
-     * - The DMA request is not a read (what happens for a address_space_map
-     *   with is_write=True? Can the device use the same pointer to do reads?)
      * - The DMA request hits past the bounds of our RAM
      */
     if (dma_patterns->len == 0
         || len == 0
         || mr != current_machine->ram
-        || is_write
         || addr > current_machine->ram_size) {
         return;
     }
@@ -213,12 +210,12 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write)
             double_fetch = true;
             if (addr < region.addr
                 && avoid_double_fetches) {
-                fuzz_dma_read_cb(addr, region.addr - addr, mr, is_write);
+                fuzz_dma_read_cb(addr, region.addr - addr, mr);
             }
             if (addr + len > region.addr + region.size
                 && avoid_double_fetches) {
                 fuzz_dma_read_cb(region.addr + region.size,
-                        addr + len - (region.addr + region.size), mr, is_write);
+                        addr + len - (region.addr + region.size), mr);
             }
             return;
         }
-- 
2.28.0