avcodec/fitsdec: Fail on 0 naxisn

Fixes: Timeout (100+ sec -> 23ms)
Fixes: 17769/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FITS_fuzzer-5678314672357376
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/fitsdec.c b/libavcodec/fitsdec.c
index a20b8faf9e9c574ba0d1a10aa8ca1f9051b27d03..1f06754f8b1e3ab2fc87357d3bc8d27868e2dd2a 100644 (file)
--- a/libavcodec/fitsdec.c
+++ b/libavcodec/fitsdec.c
@@ -143,7 +143,7 @@ static int fits_read_header(AVCodecContext *avctx, const uint8_t **ptr, FITSHead
 
     size = abs(header->bitpix) >> 3;
     for (i = 0; i < header->naxis; i++) {
-        if (size && header->naxisn[i] > SIZE_MAX / size) {
+        if (size == 0 || header->naxisn[i] > SIZE_MAX / size) {
             av_log(avctx, AV_LOG_ERROR, "unsupported size of FITS image");
             return AVERROR_INVALIDDATA;
         }