avcodec/pnm: Optimize reading loop in pnm_get()

Fixes: Timeout 13149 (5sec -> 3sec), 13166 (11sec -> 7sec), 13430 (5sec -> 3sec)
Fixes: 13149/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PGM_fuzzer-5760833622114304
Fixes: 13166/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PGMYUV_fuzzer-5763216322330624
Fixes: 13430/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PPM_fuzzer-5758658334425088
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/pnm.c b/libavcodec/pnm.c
index 17926f256f4d7a88ddb85af57f0530820b7232f0..a9771710c2a68003bfd565383b34e192dcb7d05c 100644 (file)
--- a/libavcodec/pnm.c
+++ b/libavcodec/pnm.c
@@ -52,12 +52,13 @@ static void pnm_get(PNMContext *sc, char *str, int buf_size)
     }
 
     s = str;
-    while (bs < end && !pnm_space(c)) {
-        if ((s - str)  < buf_size - 1)
-            *s++ = c;
+    while (bs < end && !pnm_space(c) && (s - str) < buf_size - 1) {
+        *s++ = c;
         c = *bs++;
     }
     *s = '\0';
+    while (bs < end && !pnm_space(c))
+        c = *bs++;
     sc->bytestream = bs;
 }