[FFmpeg-devel] [PATCH] Fix signed integer overflows

[Vitaly Buka]

Signed integer overflow is undefined behavior.
Detected with clang and -fsanitize=signed-integer-overflow

Signed-off-by: Vitaly Buka <vitalybuka at google.com>
---
 libavcodec/utils.c    | 2 +-
 libavformat/aviobuf.c | 4 +++-
 libavformat/mov.c     | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 1336e921c9..024dc1f3e2 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -971,7 +971,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         }
 
         if (!avctx->rc_initial_buffer_occupancy)
-            avctx->rc_initial_buffer_occupancy = avctx->rc_buffer_size * 3 / 4;
+            avctx->rc_initial_buffer_occupancy = avctx->rc_buffer_size * 3ll / 4;
 
         if (avctx->ticks_per_frame && avctx->time_base.num &&
             avctx->ticks_per_frame > INT_MAX / avctx->time_base.num) {
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 7f4e740a33..319a402faf 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -259,7 +259,9 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
         offset1 = pos + (s->buf_ptr - s->buffer);
         if (offset == 0)
             return offset1;
-        offset += offset1;
+        // Use unsigned type to avoid undefined behavior of singed overflow.
+        // Code below will report error on overflow anyway.
+        offset += (uint64_t)offset1;
     }
     if (offset < 0)
         return AVERROR(EINVAL);
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 522ce60c2d..a14c9f182b 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5572,7 +5572,7 @@ static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     if (atom.size < 0)
         atom.size = INT64_MAX;
-    while (total_size + 8 <= atom.size && !avio_feof(pb)) {
+    while (total_size <= atom.size - 8 && !avio_feof(pb)) {
         int (*parse)(MOVContext*, AVIOContext*, MOVAtom) = NULL;
         a.size = atom.size;
         a.type=0;
-- 
2.14.1.480.gb18f417b89-goog