[FFmpeg-devel] [PATCH] Add and use av_fast_padded_malloc.

[Reimar Döffinger]

The same as av_fast_malloc but uses av_mallocz and keeps extra
always-0 padding.
This does not mean the memory will be 0-initialized after each call,
but actually only after each growth of the buffer.
However this makes sure that
a) all data anywhere in the buffer is always initialized
b) the padding is always 0
c) the user does not have to bother with adding the padding themselves
Fixes another valgrind warning about use of uninitialized data,
this time with fate-vsynth1-jpegls.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
---
 libavcodec/asv1.c     |    3 +--
 libavcodec/avcodec.h  |    9 +++++++++
 libavcodec/eatqi.c    |    2 +-
 libavcodec/mjpegdec.c |   10 +++-------
 libavcodec/utils.c    |   24 +++++++++++++++++++++---
 5 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/libavcodec/asv1.c b/libavcodec/asv1.c
index a2519cb..9eeec26 100644
--- a/libavcodec/asv1.c
+++ b/libavcodec/asv1.c
@@ -408,10 +408,9 @@ static int decode_frame(AVCodecContext *avctx,
     p->pict_type= AV_PICTURE_TYPE_I;
     p->key_frame= 1;
 
-    av_fast_malloc(&a->bitstream_buffer, &a->bitstream_buffer_size, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
+    av_fast_padded_malloc(&a->bitstream_buffer, &a->bitstream_buffer_size, buf_size);
     if (!a->bitstream_buffer)
         return AVERROR(ENOMEM);
-    memset(a->bitstream_buffer + buf_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
 
     if(avctx->codec_id == CODEC_ID_ASV1)
         a->dsp.bswap_buf((uint32_t*)a->bitstream_buffer, (const uint32_t*)buf, buf_size/4);
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 4e55e0e..0fdff18 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -4666,6 +4666,15 @@ void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
 void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size);
 
 /**
+ * Same behaviour av_fast_malloc but the buffer has additional
+ * FF_INPUT_PADDING_SIZE at the end which will will always be 0.
+ *
+ * In addition the whole buffer will initially and after resizes
+ * be 0-initialized so that no uninitialized data will ever appear.
+ */
+void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size);
+
+/**
  * Copy image src to dst. Wraps av_picture_data_copy() above.
  */
 void av_picture_copy(AVPicture *dst, const AVPicture *src,
diff --git a/libavcodec/eatqi.c b/libavcodec/eatqi.c
index 245c143..d650a71 100644
--- a/libavcodec/eatqi.c
+++ b/libavcodec/eatqi.c
@@ -127,7 +127,7 @@ static int tqi_decode_frame(AVCodecContext *avctx,
         return -1;
     }
 
-    av_fast_malloc(&t->bitstream_buf, &t->bitstream_buf_size, (buf_end-buf) + FF_INPUT_BUFFER_PADDING_SIZE);
+    av_fast_padded_malloc(&t->bitstream_buf, &t->bitstream_buf_size, buf_end-buf);
     if (!t->bitstream_buf)
         return AVERROR(ENOMEM);
     s->dsp.bswap_buf(t->bitstream_buf, (const uint32_t*)buf, (buf_end-buf)/4);
diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index ad78b4c..2abfea0 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -1474,13 +1474,9 @@ int ff_mjpeg_find_marker(MJpegDecodeContext *s,
     int start_code;
     start_code = find_marker(buf_ptr, buf_end);
 
-    if ((buf_end - *buf_ptr) > s->buffer_size) {
-        av_free(s->buffer);
-        s->buffer_size = buf_end - *buf_ptr;
-        s->buffer      = av_malloc(s->buffer_size + FF_INPUT_BUFFER_PADDING_SIZE);
-        av_log(s->avctx, AV_LOG_DEBUG,
-               "buffer too small, expanding to %d bytes\n", s->buffer_size);
-    }
+    av_fast_padded_malloc(&s->buffer, &s->buffer_size, buf_end - *buf_ptr);
+    if (!s->buffer)
+        return AVERROR(ENOMEM);
 
     /* unescape buffer of SOS, use special treatment for JPEG-LS */
     if (start_code == SOS && !s->ls) {
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index ec03b90..0b2a99f 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -68,16 +68,34 @@ void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
     return ptr;
 }
 
-void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
+static inline int ff_fast_malloc(void *ptr, unsigned int *size, size_t min_size, int zero_realloc)
 {
     void **p = ptr;
     if (min_size < *size)
-        return;
+        return 0;
     min_size= FFMAX(17*min_size/16 + 32, min_size);
     av_free(*p);
-    *p = av_malloc(min_size);
+    *p = zero_realloc ? av_mallocz(min_size) : av_malloc(min_size);
     if (!*p) min_size = 0;
     *size= min_size;
+    return 1;
+}
+
+void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
+{
+    ff_fast_malloc(ptr, size, min_size, 0);
+}
+
+void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size)
+{
+    uint8_t **p = ptr;
+    if (min_size > SIZE_MAX - FF_INPUT_BUFFER_PADDING_SIZE) {
+        *p = NULL;
+        *size = 0;
+        return;
+    }
+    if (!ff_fast_malloc(p, size, min_size + FF_INPUT_BUFFER_PADDING_SIZE, 1))
+        memset(*p + min_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
 }
 
 /* encoder management */
-- 
1.7.8.3