Re: [FFmpeg-devel] [PATCH] tools: Add target_sws_fuzzer.c

[James Almer <jamrial@gmail.com>]

On 2/17/2024 10:03 PM, Michael Niedermayer wrote:
> On Sat, Feb 17, 2024 at 09:13:21PM -0300, James Almer wrote:
>>
>>
>> On 2/17/2024 8:48 PM, Michael Niedermayer wrote:
>>> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>>> ---
>>>    Makefile                  |   3 +
>>>    tools/Makefile            |   3 +
>>>    tools/target_sws_fuzzer.c | 168 ++++++++++++++++++++++++++++++++++++++
>>>    3 files changed, 174 insertions(+)
>>>    create mode 100644 tools/target_sws_fuzzer.c
>>>
>>> diff --git a/Makefile b/Makefile
>>> index dbc930270b3..b309dbc4db9 100644
>>> --- a/Makefile
>>> +++ b/Makefile
>>> @@ -64,6 +64,9 @@ tools/target_dem_fuzzer$(EXESUF): tools/target_dem_fuzzer.o $(FF_DEP_LIBS)
>>>    tools/target_io_dem_fuzzer$(EXESUF): tools/target_io_dem_fuzzer.o $(FF_DEP_LIBS)
>>>    	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $^ $(ELIBS) $(FF_EXTRALIBS) $(LIBFUZZER_PATH)
>>> +tools/target_sws_fuzzer$(EXESUF): tools/target_sws_fuzzer.o $(FF_DEP_LIBS)
>>> +	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $^ $(ELIBS) $(FF_EXTRALIBS) $(LIBFUZZER_PATH)
>>> +
>>>    tools/enum_options$(EXESUF): ELIBS = $(FF_EXTRALIBS)
>>>    tools/enum_options$(EXESUF): $(FF_DEP_LIBS)
>>> diff --git a/tools/Makefile b/tools/Makefile
>>> index dee6a416688..72e8e709a8d 100644
>>> --- a/tools/Makefile
>>> +++ b/tools/Makefile
>>> @@ -17,6 +17,9 @@ tools/target_dem_fuzzer.o: tools/target_dem_fuzzer.c
>>>    tools/target_io_dem_fuzzer.o: tools/target_dem_fuzzer.c
>>>    	$(COMPILE_C) -DIO_FLAT=0
>>> +tools/target_sws_fuzzer.o: tools/target_sws_fuzzer.c
>>> +	$(COMPILE_C)
>>> +
>>>    tools/enc_recon_frame_test$(EXESUF): tools/decode_simple.o
>>>    tools/venc_data_dump$(EXESUF): tools/decode_simple.o
>>>    tools/scale_slice_test$(EXESUF): tools/decode_simple.o
>>> diff --git a/tools/target_sws_fuzzer.c b/tools/target_sws_fuzzer.c
>>> new file mode 100644
>>> index 00000000000..babb6e81629
>>> --- /dev/null
>>> +++ b/tools/target_sws_fuzzer.c
>>> @@ -0,0 +1,168 @@
>>> +/*
>>> + * Copyright (c) 2024 Michael Niedermayer <michael-ffmpeg@niedermayer.cc>
>>> + *
>>> + * This file is part of FFmpeg.
>>> + *
>>> + * FFmpeg is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU Lesser General Public
>>> + * License as published by the Free Software Foundation; either
>>> + * version 2.1 of the License, or (at your option) any later version.
>>> + *
>>> + * FFmpeg is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> + * Lesser General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU Lesser General Public
>>> + * License along with FFmpeg; if not, write to the Free Software
>>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>>> + */
>>> +
>>> +#include "config.h"
>>> +#include "libavutil/avassert.h"
>>> +#include "libavutil/avstring.h"
>>> +#include "libavutil/cpu.h"
>>> +#include "libavutil/imgutils.h"
>>> +#include "libavutil/intreadwrite.h"
>>> +#include "libavutil/opt.h"
>>> +
>>> +#include "libavcodec/bytestream.h"
>>> +
>>> +#include "libswscale/swscale.h"
>>> +
>>> +
>>> +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
>>> +
>>> +static void error(const char *err)
>>> +{
>>> +    fprintf(stderr, "%s", err);
>>> +    exit(1);
>>> +}
>>> +
>>> +static int alloc_plane(uint8_t *data[AV_VIDEO_MAX_PLANES], int stride[AV_VIDEO_MAX_PLANES], int w, int h, int format, int *hshift, int *vshift)
>>> +{
>>> +    int ret = av_image_fill_linesizes(stride, format, w);
>>> +    if (ret < 0)
>>> +        return -1;
>>> +
>>> +    av_pix_fmt_get_chroma_sub_sample(format, hshift, vshift);
>>> +
>>> +    for(int p=0; p<AV_VIDEO_MAX_PLANES; p++) {
>>> +        if (stride[p]) {
>>> +            stride[p] = FFALIGN(stride[p], 32);
>>> +            int ph = AV_CEIL_RSHIFT(h, (p == 1 || p == 2) ? *vshift : 0);
>>> +            av_log(0,0, "P:%d St %d ph %d\n", p, stride[p], ph);
>>> +            data[p] = av_mallocz(stride[p] * ph + 32);
>>> +            if (!data[p])
>>> +                return -1;
>>> +        }
>>> +    }
>>> +    if (format == AV_PIX_FMT_PAL8) {
>>> +        data[1] = av_mallocz(256*4);
>>> +        if (!data[1])
>>> +            return -1;
>>> +    }
>>> +    return 0;
>>
>> av_image_alloc()? Would be better to actually test sws with buffers created
>> by our own public helpers.
> 
> av_image_alloc() allocates the planes in one continous piece
> so teh fuzzer would not be able to detect accesses over the end of the first
> or accesses prior the 2nd.
> 
> So this is not possible

Then use av_image_fill_plane_sizes() after av_image_fill_linesizes() and 
then allocate the buffers with its output. See fuzz_video_get_buffer() 
in test_dec_fuzzer.c
It's best if we don't rewrite basic buffer allocation and size 
calculation functions every time we add new code.

> 
> 
>>
>>> +}
>>> +
>>> +static void free_plane(uint8_t *data[AV_VIDEO_MAX_PLANES])
>>> +{
>>> +    for(int p=0; p<AV_VIDEO_MAX_PLANES; p++)
>>> +        av_freep(&data[p]);
>>> +}
>>> +
>>> +int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
>>> +    int srcW= 48, srcH = 48;
>>> +    int dstW= 48, dstH = 48;
>>> +    int srcHShift, srcVShift;
>>> +    int dstHShift, dstVShift;
>>> +    unsigned flags = 1;
>>> +    int srcStride[AV_VIDEO_MAX_PLANES] = {0};
>>> +    int dstStride[AV_VIDEO_MAX_PLANES] = {0};
>>> +    int ret;
>>> +    const uint8_t *end = data + size;
>>> +    enum AVPixelFormat srcFormat = AV_PIX_FMT_YUV420P;
>>> +    enum AVPixelFormat dstFormat = AV_PIX_FMT_YUV420P;
>>> +    uint8_t *src[4] = { 0 };
>>> +    uint8_t *dst[4] = { 0 };
>>
>> AV_VIDEO_MAX_PLANES.
> 
> will change
> 
> 
>>
>>> +    struct SwsContext *sws = NULL;
>>> +    const AVPixFmtDescriptor *desc_src, *desc_dst;
>>> +
>>> +    if (size > 128) {
>>> +        GetByteContext gbc;
>>> +        int64_t flags64;
>>> +
>>> +        size -= 128;
>>> +        bytestream2_init(&gbc, data + size, 128);
>>> +        srcW = bytestream2_get_le32(&gbc) % 256;
>>> +        srcH = bytestream2_get_le32(&gbc) % 256;
>>> +        dstW = bytestream2_get_le32(&gbc) % 256;
>>> +        dstH = bytestream2_get_le32(&gbc) % 256;
>>> +        flags = bytestream2_get_le32(&gbc);
>>> +
>>> +        srcFormat = bytestream2_get_le32(&gbc) % AV_PIX_FMT_NB;
>>> +        dstFormat = bytestream2_get_le32(&gbc) % AV_PIX_FMT_NB;
>>
>> nit: Maybe sanitize the choices with sws_isSupportedInput() and
>> sws_isSupportedOutput()? Unless having sws_init_context() fail with invalid
>> arguments is also intended.
> 
> Honestly i do not know which way is best

Leave it as is, it's not important.

> 
> 
>>
>>> +
>>> +        flags64 = bytestream2_get_le64(&gbc);
>>> +        if (flags64 & 0x10)
>>> +            av_force_cpu_flags(0);
>>> +
>>> +        if (av_image_check_size(srcW, srcH, srcFormat, NULL))
>>> +            srcW = srcH = 123;
>>> +        if (av_image_check_size(dstW, dstH, dstFormat, NULL))
>>> +            dstW = dstH = 123;
>>
>> Is there a format where this could fail, knowing the dimensions are at most
>> 255x255?
> 
> The 255 is temporary, a less restrictive size should be choosen as there may
> be bugs with huge sizes. Its just that these really slow it down
> 
> 
>>
>>> +        //TODO alphablend
>>> +    }
>>> +
>>> +    desc_src = av_pix_fmt_desc_get(srcFormat);
>>> +    desc_dst = av_pix_fmt_desc_get(dstFormat);
>>> +
>>> +    ret = alloc_plane(src, srcStride, srcW, srcH, srcFormat, &srcHShift, &srcVShift);
>>> +    if (ret < 0)
>>> +        goto end;
>>> +
>>> +    ret = alloc_plane(dst, dstStride, dstW, dstH, dstFormat, &dstHShift, &dstVShift);
>>> +    if (ret < 0)
>>> +        goto end;
>>> +
>>> +
>>> +    for(int p=0; p<AV_VIDEO_MAX_PLANES; p++) {
>>> +        int psize = srcStride[p] * AV_CEIL_RSHIFT(srcH, (p == 1 || p == 2) ? srcVShift : 0);
>>> +        if (psize > size)
>>> +            psize = size;
>>> +        if (psize) {
>>> +            memcpy(src[p], data, psize);
>>> +            data += psize;
>>> +            size -= psize;
>>> +        }
>>> +    }
>>
>> av_image_copy(). Or av_image_copy_plane() in a loop if you prefer.
> 
> these dont seem to have a input size so ill leave it for now

Ok.

> 
> thx
> 
> [...]
> 
> 
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