[FFmpeg-cvslog] avcodec/pnm: Check scale

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sat Jun  6 17:50:21 2020 +0200| [8e21379da110ca78f41ff2fe074fd771a1bcd1d0] | committer: Michael Niedermayer

avcodec/pnm: Check scale

Fixes: division by zero
Fixes: 22974/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PFM_fuzzer-6270027077779456

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8e21379da110ca78f41ff2fe074fd771a1bcd1d0
---

 libavcodec/pnm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/pnm.c b/libavcodec/pnm.c
index a6ae01b494..aad23c7ae2 100644
--- a/libavcodec/pnm.c
+++ b/libavcodec/pnm.c
@@ -179,7 +179,7 @@ int ff_pnm_decode_header(AVCodecContext *avctx, PNMContext * const s)
 
     if (avctx->pix_fmt == AV_PIX_FMT_GBRPF32) {
         pnm_get(s, buf1, sizeof(buf1));
-        if (av_sscanf(buf1, "%f", &s->scale) != 1) {
+        if (av_sscanf(buf1, "%f", &s->scale) != 1 || s->scale == 0.0 || !isfinite(s->scale)) {
             av_log(avctx, AV_LOG_ERROR, "Invalid scale.\n");
             return AVERROR_INVALIDDATA;
         }