[FFmpeg-cvslog] avcodec/movtextdec: Fix leaks of strings upon reallocation failure

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Sat Oct 17 12:32:54 2020 +0200| [38cdd27e9b36183a74c19859a8092aca6e82d712] | committer: Andreas Rheinhardt

avcodec/movtextdec: Fix leaks of strings upon reallocation failure

Up until now, the 3GPP Timed Text decoder used av_dynarray_add()
for a list of font entries, a structure which contains an allocated
string. The font entries are owned by the pointers in the dynamic array
and are therefore unsuitable for av_dynarray_add() which simply frees
the array, but not the font entries and of course not the strings. The
latter all leak if reallocating the dynamic array fails.

This commit fixes this. It stops reallocating the array altogether:
After all, the final number of elements (pending errors) is already
known in advance.

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

Reviewed-by: Philip Langdale <philipl at overt.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=38cdd27e9b36183a74c19859a8092aca6e82d712
---

 libavcodec/movtextdec.c | 61 +++++++++++++++++++------------------------------
 1 file changed, 24 insertions(+), 37 deletions(-)

diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index 068bdb7802..ad60c77519 100644
--- a/libavcodec/movtextdec.c
+++ b/libavcodec/movtextdec.c
@@ -102,15 +102,14 @@ typedef struct {
     StyleBox *s_temp;
     HighlightBox h;
     HilightcolorBox c;
-    FontRecord **ftab;
-    FontRecord *ftab_temp;
+    FontRecord *ftab;
     TextWrapBox w;
     MovTextDefault d;
     uint8_t box_flags;
     uint16_t style_entries, ftab_entries;
     uint64_t tracksize;
     int size_var;
-    int count_s, count_f;
+    int count_s;
     int readorder;
     int frame_width;
     int frame_height;
@@ -137,16 +136,8 @@ static void mov_text_cleanup(MovTextContext *m)
 
 static void mov_text_cleanup_ftab(MovTextContext *m)
 {
-    int i;
-    if (m->ftab_temp)
-        av_freep(&m->ftab_temp->font);
-    av_freep(&m->ftab_temp);
-    if (m->ftab) {
-        for(i = 0; i < m->count_f; i++) {
-            av_freep(&m->ftab[i]->font);
-            av_freep(&m->ftab[i]);
-        }
-    }
+    for (unsigned i = 0; i < m->ftab_entries; i++)
+        av_freep(&m->ftab[i].font);
     av_freep(&m->ftab);
     m->ftab_entries = 0;
 }
@@ -156,9 +147,9 @@ static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
     uint8_t *tx3g_ptr = avctx->extradata;
     int i, box_size, font_length;
     int8_t v_align, h_align;
+    unsigned ftab_entries;
     StyleBox s_default;
 
-    m->count_f = 0;
     m->ftab_entries = 0;
     box_size = BOX_SIZE_INITIAL; /* Size till ftab_entries */
     if (avctx->extradata_size < box_size)
@@ -223,7 +214,16 @@ static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
     // ftab
     tx3g_ptr += 4;
 
-    m->ftab_entries = AV_RB16(tx3g_ptr);
+    // In case of broken header, init default font
+    m->d.font = ASS_DEFAULT_FONT;
+
+    ftab_entries = AV_RB16(tx3g_ptr);
+    if (!ftab_entries)
+        return 0;
+    m->ftab = av_calloc(ftab_entries, sizeof(*m->ftab));
+    if (!m->ftab)
+        return AVERROR(ENOMEM);
+    m->ftab_entries = ftab_entries;
     tx3g_ptr += 2;
 
     for (i = 0; i < m->ftab_entries; i++) {
@@ -233,12 +233,7 @@ static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
             mov_text_cleanup_ftab(m);
             return -1;
         }
-        m->ftab_temp = av_mallocz(sizeof(*m->ftab_temp));
-        if (!m->ftab_temp) {
-            mov_text_cleanup_ftab(m);
-            return AVERROR(ENOMEM);
-        }
-        m->ftab_temp->fontID = AV_RB16(tx3g_ptr);
+        m->ftab[i].fontID = AV_RB16(tx3g_ptr);
         tx3g_ptr += 2;
         font_length = *tx3g_ptr++;
 
@@ -247,26 +242,18 @@ static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
             mov_text_cleanup_ftab(m);
             return -1;
         }
-        m->ftab_temp->font = av_malloc(font_length + 1);
-        if (!m->ftab_temp->font) {
+        m->ftab[i].font = av_malloc(font_length + 1);
+        if (!m->ftab[i].font) {
             mov_text_cleanup_ftab(m);
             return AVERROR(ENOMEM);
         }
-        memcpy(m->ftab_temp->font, tx3g_ptr, font_length);
-        m->ftab_temp->font[font_length] = '\0';
-        av_dynarray_add(&m->ftab, &m->count_f, m->ftab_temp);
-        if (!m->ftab) {
-            mov_text_cleanup_ftab(m);
-            return AVERROR(ENOMEM);
-        }
-        m->ftab_temp = NULL;
+        memcpy(m->ftab[i].font, tx3g_ptr, font_length);
+        m->ftab[i].font[font_length] = '\0';
         tx3g_ptr = tx3g_ptr + font_length;
     }
-    // In case of broken header, init default font
-    m->d.font = ASS_DEFAULT_FONT;
     for (i = 0; i < m->ftab_entries; i++) {
-        if (m->d.fontID == m->ftab[i]->fontID)
-            m->d.font = m->ftab[i]->font;
+        if (m->d.fontID == m->ftab[i].fontID)
+            m->d.font = m->ftab[i].font;
     }
     return 0;
 }
@@ -405,8 +392,8 @@ static int text_to_ass(AVBPrint *buf, const char *text, const char *text_end,
                     av_bprintf(buf, "{\\fs%d}", m->s[entry]->fontsize);
                 if (m->s[entry]->style_fontID != m->d.fontID)
                     for (i = 0; i < m->ftab_entries; i++) {
-                        if (m->s[entry]->style_fontID == m->ftab[i]->fontID)
-                            av_bprintf(buf, "{\\fn%s}", m->ftab[i]->font);
+                        if (m->s[entry]->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;