avcodec/movtextdec: Fix leaks on (re)allocation failure

Up until now, the 3GPP Timed Text decoder used av_dynarray_add()
for a list of style entries. Said entries are individually allocated
and owned by the pointers in the dynamic array and are therefore
unsuitable for av_dynarray_add() which simply frees the array,
but not the entries on error. In this case the intended new entry
also leaks because it has been forgotten to free it.

This commit fixes this. It is now allocated in one go and not
reallocated multiple times (and it won't be overallocated any more).
After all, the final number of elements (pending errors) is already
known in advance.

Furthermore, the style entries are now the entries of the new array,
i.e. they are no longer allocated separately. This also removes one
level of indirection.

Reviewed-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 94ad68ee17420996c9b003f142717d82b52c0915)

1 files changed, 36 insertions, 48 deletions

diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index e46c932c20..02e2a58f56 100644
--- a/libavcodec/movtextdec.c
+++ b/libavcodec/movtextdec.c
@@ -98,8 +98,7 @@ typedef struct {
 
 typedef struct {
     AVClass *class;
-    StyleBox **s;
-    StyleBox *s_temp;
+    StyleBox *s;
     HighlightBox h;
     HilightcolorBox c;
     FontRecord *ftab;
@@ -109,7 +108,6 @@ typedef struct {
     uint16_t style_entries, ftab_entries;
     uint64_t tracksize;
     int size_var;
-    int count_s;
     int readorder;
     int frame_width;
     int frame_height;
@@ -123,13 +121,8 @@ typedef struct {
 
 static void mov_text_cleanup(MovTextContext *m)
 {
-    int i;
     if (m->box_flags & STYL_BOX) {
-        for(i = 0; i < m->count_s; i++) {
-            av_freep(&m->s[i]);
-        }
         av_freep(&m->s);
-        m->count_s = 0;
         m->style_entries = 0;
     }
 }
@@ -283,50 +276,45 @@ static int decode_styl(const uint8_t *tsmb, MovTextContext *m, AVPacket *avpkt)
 {
     int i;
     int style_entries = AV_RB16(tsmb);
+    StyleBox *tmp;
     tsmb += 2;
     // A single style record is of length 12 bytes.
     if (m->tracksize + m->size_var + 2 + style_entries * 12 > avpkt->size)
         return -1;
 
+    tmp = av_realloc_array(m->s, style_entries, sizeof(*m->s));
+    if (!tmp)
+        return AVERROR(ENOMEM);
+    m->s             = tmp;
     m->style_entries = style_entries;
 
     m->box_flags |= STYL_BOX;
     for(i = 0; i < m->style_entries; i++) {
-        m->s_temp = av_malloc(sizeof(*m->s_temp));
-        if (!m->s_temp) {
-            mov_text_cleanup(m);
-            return AVERROR(ENOMEM);
-        }
-        m->s_temp->style_start = AV_RB16(tsmb);
+        StyleBox *style = &m->s[i];
+        style->style_start = AV_RB16(tsmb);
         tsmb += 2;
-        m->s_temp->style_end = AV_RB16(tsmb);
+        style->style_end = AV_RB16(tsmb);
 
-        if (   m->s_temp->style_end < m->s_temp->style_start
-            || (m->count_s && m->s_temp->style_start < m->s[m->count_s - 1]->style_end)) {
-            av_freep(&m->s_temp);
+        if (   style->style_end < style->style_start
+            || (i && style->style_start < m->s[i - 1].style_end)) {
             mov_text_cleanup(m);
             return AVERROR(ENOMEM);
         }
 
         tsmb += 2;
-        m->s_temp->style_fontID = AV_RB16(tsmb);
+        style->style_fontID = AV_RB16(tsmb);
         tsmb += 2;
-        m->s_temp->style_flag = AV_RB8(tsmb);
-        m->s_temp->bold = !!(m->s_temp->style_flag & STYLE_FLAG_BOLD);
-        m->s_temp->italic = !!(m->s_temp->style_flag & STYLE_FLAG_ITALIC);
-        m->s_temp->underline = !!(m->s_temp->style_flag & STYLE_FLAG_UNDERLINE);
+        style->style_flag = AV_RB8(tsmb);
+        style->bold      = !!(style->style_flag & STYLE_FLAG_BOLD);
+        style->italic    = !!(style->style_flag & STYLE_FLAG_ITALIC);
+        style->underline = !!(style->style_flag & STYLE_FLAG_UNDERLINE);
         tsmb++;
-        m->s_temp->fontsize = AV_RB8(tsmb);
+        style->fontsize = AV_RB8(tsmb);
         tsmb++;
-        m->s_temp->color = AV_RB24(tsmb);
+        style->color = AV_RB24(tsmb);
         tsmb += 3;
-        m->s_temp->alpha = AV_RB8(tsmb);
+        style->alpha = AV_RB8(tsmb);
         tsmb++;
-        av_dynarray_add(&m->s, &m->count_s, m->s_temp);
-        if(!m->s) {
-            mov_text_cleanup(m);
-            return AVERROR(ENOMEM);
-        }
     }
     return 0;
 }
@@ -376,29 +364,30 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
         int len;
 
         if ((m->box_flags & STYL_BOX) && entry < m->style_entries) {
-            if (text_pos == m->s[entry]->style_start) {
+            const StyleBox *style = &m->s[entry];
+            if (text_pos == style->style_start) {
                 style_active = 1;
-                if (m->s[entry]->bold ^ m->d.bold)
-                    av_bprintf(buf, "{\\b%d}", m->s[entry]->bold);
-                if (m->s[entry]->italic ^ m->d.italic)
-                    av_bprintf(buf, "{\\i%d}", m->s[entry]->italic);
-                if (m->s[entry]->underline ^ m->d.underline)
-                    av_bprintf(buf, "{\\u%d}", m->s[entry]->underline);
-                if (m->s[entry]->fontsize != m->d.fontsize)
-                    av_bprintf(buf, "{\\fs%d}", m->s[entry]->fontsize);
-                if (m->s[entry]->style_fontID != m->d.fontID)
+                if (style->bold ^ m->d.bold)
+                    av_bprintf(buf, "{\\b%d}", style->bold);
+                if (style->italic ^ m->d.italic)
+                    av_bprintf(buf, "{\\i%d}", style->italic);
+                if (style->underline ^ m->d.underline)
+                    av_bprintf(buf, "{\\u%d}", style->underline);
+                if (style->fontsize != m->d.fontsize)
+                    av_bprintf(buf, "{\\fs%d}", style->fontsize);
+                if (style->style_fontID != m->d.fontID)
                     for (i = 0; i < m->ftab_entries; i++) {
-                        if (m->s[entry]->style_fontID == m->ftab[i].fontID)
+                        if (style->style_fontID == m->ftab[i].fontID)
                             av_bprintf(buf, "{\\fn%s}", m->ftab[i].font);
                     }
-                if (m->d.color != m->s[entry]->color) {
-                    color = m->s[entry]->color;
+                if (m->d.color != style->color) {
+                    color = style->color;
                     av_bprintf(buf, "{\\1c&H%X&}", RGB_TO_BGR(color));
                 }
-                if (m->d.alpha != m->s[entry]->alpha)
-                    av_bprintf(buf, "{\\1a&H%02X&}", 255 - m->s[entry]->alpha);
+                if (m->d.alpha != style->alpha)
+                    av_bprintf(buf, "{\\1a&H%02X&}", 255 - style->alpha);
             }
-            if (text_pos == m->s[entry]->style_end) {
+            if (text_pos == style->style_end) {
                 if (style_active) {
                     av_bprintf(buf, "{\\r}");
                     style_active = 0;
@@ -526,7 +515,6 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
     m->tracksize = 2 + text_length;
     m->style_entries = 0;
     m->box_flags = 0;
-    m->count_s = 0;
     // Note that the spec recommends lines be no longer than 2048 characters.
     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
     if (text_length + 2 != avpkt->size) {