From: Stefan Hajnoczi <stefanha@gmail.com>
To: "Oleinik, Alexander" <alxndr@bu.edu>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: [PATCH v4 15/20] fuzz: add fuzzer skeleton
Date: Thu, 7 Nov 2019 13:55:40 +0100 [thread overview]
Message-ID: <20191107125540.GA365089@stefanha-x1.localdomain> (raw)
In-Reply-To: <20191030144926.11873-16-alxndr@bu.edu>
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On Wed, Oct 30, 2019 at 02:50:00PM +0000, Oleinik, Alexander wrote:
> diff --git a/tests/fuzz/fuzz.c b/tests/fuzz/fuzz.c
> new file mode 100644
> index 0000000000..0e38f81c48
> --- /dev/null
> +++ b/tests/fuzz/fuzz.c
> @@ -0,0 +1,177 @@
> +/*
> + * fuzzing driver
> + *
> + * Copyright Red Hat Inc., 2019
> + *
> + * Authors:
> + * Alexander Bulekov <alxndr@bu.edu>
Bulekov instead of Oleinik?
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include <stdio.h>
> +#include <stdlib.h>
stdio.h and stdlib.h are already included by qemu/osdep.h.
> +/* Executed for each fuzzing-input */
> +int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size)
> +{
> + if (fuzz_target->fuzz) {
Will this ever be NULL?
> + fuzz_target->fuzz(fuzz_qts, Data, Size);
> + }
> + return 0;
> +}
> +
> +/* Executed once, prior to fuzzing */
> +int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
> +{
> +
> + char *target_name;
> +
> + /* Initialize qgraph and modules */
> + qos_graph_init();
> + module_call_init(MODULE_INIT_FUZZ_TARGET);
> + module_call_init(MODULE_INIT_QOM);
> + module_call_init(MODULE_INIT_LIBQOS);
> +
> + if (*argc <= 1) {
> + usage(**argv);
> + }
> +
> + /* Identify the fuzz target */
> + target_name = (*argv)[1];
> + if (!strstr(target_name, "--fuzz-target=")) {
> + usage(**argv);
> + }
> +
> + target_name += strlen("--fuzz-target=");
> +
> + fuzz_target = fuzz_get_target(target_name);
> + if (!fuzz_target) {
> + usage(**argv);
> + }
> +
> + fuzz_qts = qtest_setup();
> +
> + if (!fuzz_target) {
This is dead code since fuzz_target was already checked above. Please
remove this if statement.
> + fprintf(stderr, "Error: Fuzz fuzz_target name %s not found\n",
> + target_name);
> + usage(**argv);
> + }
> +
> + if (fuzz_target->pre_vm_init) {
> + fuzz_target->pre_vm_init();
> + }
> +
> + /* Run QEMU's softmmu main with the fuzz-target dependent arguments */
> + char *init_cmdline = fuzz_target->get_init_cmdline(fuzz_target);
Where is init_cmdline freed or should this be const char *?
> + wordexp_t result;
> + wordexp(init_cmdline, &result, 0);
What is the purpose of word expansion here?
> +
> + qemu_init(result.we_wordc, result.we_wordv, NULL);
> +
> + if (fuzz_target->pre_fuzz) {
> + fuzz_target->pre_fuzz(fuzz_qts);
> + }
> +
> + return 0;
> +}
> diff --git a/tests/fuzz/fuzz.h b/tests/fuzz/fuzz.h
> new file mode 100644
> index 0000000000..b569b622d7
> --- /dev/null
> +++ b/tests/fuzz/fuzz.h
> @@ -0,0 +1,66 @@
> +/*
> + * fuzzing driver
> + *
> + * Copyright Red Hat Inc., 2019
> + *
> + * Authors:
> + * Alexander Bulekov <alxndr@bu.edu>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef FUZZER_H_
> +#define FUZZER_H_
> +
> +#include "qemu/osdep.h"
> +#include "qemu/units.h"
> +#include "qapi/error.h"
> +#include "exec/memory.h"
> +#include "tests/libqtest.h"
> +
> +
Some documentation would be nice:
/**
* A libfuzzer fuzzing target
*
* The QEMU fuzzing binary is built with all available targets, each
* with a unique @name that can be specified on the command-line to
* select which target should run.
*
* A target must implement ->fuzz() to process a random input. If QEMU
* crashes in ->fuzz() then libfuzzer will record a failure.
*
* Fuzzing targets are registered with fuzz_add_target():
*
* static const FuzzTarget fuzz_target = {
* .name = "my-device-fifo",
* .description = "Fuzz the FIFO buffer registers of my-device",
* ...
* };
*
* static void register_fuzz_target(void)
* {
* fuzz_add_target(&fuzz_target);
* }
* fuzz_target_init(register_fuzz_target);
*/
> +typedef struct FuzzTarget {
> + const char *name; /* command-line option(FUZZ_TARGET) for the target */
> + const char *description; /* help text */
> +
If any of the function pointers can be NULL, please document this.
> + /* returns the arg-list that is passed to qemu/softmmu init() */
> + char* (*get_init_cmdline)(struct FuzzTarget *);
Does the caller need to call g_free() on the returned string? Please
document this.
> +
> + /*
> + * will run once, prior to running qemu/softmmu init.
> + * eg: set up shared-memory for communication with the child-process
> + */
> + void(*pre_vm_init)(void);
> +
> + /*
> + * will run once, prior to to the fuzz-loop.
s/to to/to/
> + * eg: detect the memory map
> + */
> + void(*pre_fuzz)(QTestState *);
Please also mention that QEMU has been initialized at this point.
> +
> + /*
> + * accepts and executes an input from libfuzzer. this is repeatedly
> + * executed during the fuzzing loop. Its should handle setup, input
> + * execution and cleanup
> + */
> + void(*fuzz)(QTestState *, const unsigned char *, size_t);
> +
> +} FuzzTarget;
> +
> +void flush_events(QTestState *);
> +void reboot(QTestState *);
> +
> +/*
> + * makes a copy of *target and adds it to the target-list.
> + * i.e. fine to set up target on the caller's stack
> + */
> +void fuzz_add_target(FuzzTarget *target);
"makes a copy of *target" -> does this mean the argument type can be
const FuzzTarget *target?
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next prev parent reply other threads:[~2019-11-07 12:56 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-30 14:49 [PATCH v4 00/20] Add virtual device fuzzing support Oleinik, Alexander
2019-10-30 14:49 ` [PATCH v4 01/20] softmmu: split off vl.c:main() into main.c Oleinik, Alexander
2019-11-05 16:41 ` Darren Kenny
2019-11-12 16:46 ` Alexander Bulekov
2019-11-06 15:01 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 02/20] libqos: Rename i2c_send and i2c_recv Oleinik, Alexander
2019-11-06 15:17 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 03/20] fuzz: Add FUZZ_TARGET module type Oleinik, Alexander
2019-11-06 13:17 ` Darren Kenny
2019-11-06 15:18 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 04/20] qtest: add qtest_server_send abstraction Oleinik, Alexander
2019-11-06 13:29 ` Darren Kenny
2019-11-06 15:19 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 06/20] module: check module wasn't already initialized Oleinik, Alexander
2019-11-06 15:26 ` Stefan Hajnoczi
2019-11-06 17:40 ` Darren Kenny
2019-10-30 14:49 ` [PATCH v4 05/20] libqtest: Add a layer of abstraciton to send/recv Oleinik, Alexander
2019-11-06 16:22 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 07/20] qtest: add in-process incoming command handler Oleinik, Alexander
2019-11-06 16:33 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 08/20] tests: provide test variables to other targets Oleinik, Alexander
2019-11-07 14:32 ` Darren Kenny
2019-10-30 14:49 ` [PATCH v4 09/20] libqos: split qos-test and libqos makefile vars Oleinik, Alexander
2019-11-07 14:03 ` Darren Kenny
2019-10-30 14:49 ` [PATCH v4 10/20] libqos: move useful qos-test funcs to qos_external Oleinik, Alexander
2019-11-06 16:41 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 11/20] libqtest: make qtest_bufwrite send "atomic" Oleinik, Alexander
2019-11-06 16:44 ` Stefan Hajnoczi
2019-10-30 14:49 ` [PATCH v4 12/20] libqtest: add in-process qtest.c tx/rx handlers Oleinik, Alexander
2019-11-06 16:56 ` Stefan Hajnoczi
2019-11-12 17:38 ` Alexander Bulekov
2019-10-30 14:49 ` [PATCH v4 13/20] fuzz: add configure flag --enable-fuzzing Oleinik, Alexander
2019-11-06 16:57 ` Stefan Hajnoczi
2019-10-30 14:50 ` [PATCH v4 15/20] fuzz: add fuzzer skeleton Oleinik, Alexander
2019-11-07 12:55 ` Stefan Hajnoczi [this message]
2019-11-12 19:04 ` Alexander Bulekov
2019-10-30 14:50 ` [PATCH v4 14/20] fuzz: Add target/fuzz makefile rules Oleinik, Alexander
2019-11-07 14:31 ` Darren Kenny
2019-10-30 14:50 ` [PATCH v4 16/20] fuzz: add support for fork-based fuzzing Oleinik, Alexander
2019-11-07 13:17 ` Stefan Hajnoczi
2019-10-30 14:50 ` [PATCH v4 17/20] fuzz: add support for qos-assisted fuzz targets Oleinik, Alexander
2019-11-07 13:22 ` Stefan Hajnoczi
2019-10-30 14:50 ` [PATCH v4 18/20] fuzz: add i440fx " Oleinik, Alexander
2019-11-07 13:26 ` Stefan Hajnoczi
2019-10-30 14:50 ` [PATCH v4 19/20] fuzz: add virtio-net fuzz target Oleinik, Alexander
2019-11-07 13:36 ` Stefan Hajnoczi
2019-11-07 13:42 ` Jason Wang
2019-11-07 15:41 ` Stefan Hajnoczi
2019-10-30 14:50 ` [PATCH v4 20/20] fuzz: add documentation to docs/devel/ Oleinik, Alexander
2019-11-07 13:40 ` Stefan Hajnoczi
2019-11-07 15:02 ` Alexander Oleinik
2019-10-30 15:23 ` [PATCH v4 00/20] Add virtual device fuzzing support no-reply
2019-11-06 15:27 ` Stefan Hajnoczi
2019-11-05 13:57 ` Darren Kenny
2019-11-05 16:28 ` Alexander Oleinik
2019-11-05 16:47 ` Darren Kenny
2019-11-07 13:41 ` Stefan Hajnoczi
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