avcodec/hevc: Fix integer overflow of entry_point_offset

Fixes out of array read
Fixes: d41d8cd98f00b204e9800998ecf8427e/signal_sigsegv_321165b_7641_077dfcd8cbc80b1c0b470c8554cd6ffb.bit

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 21408585)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/hevc.c

@@ -744,7 +744,7 @@ static int hls_slice_header(HEVCContext *s)
             av_freep(&sh->entry_point_offset);
             av_freep(&sh->offset);
             av_freep(&sh->size);
-            sh->entry_point_offset = av_malloc_array(sh->num_entry_point_offsets, sizeof(int));
+            sh->entry_point_offset = av_malloc_array(sh->num_entry_point_offsets, sizeof(unsigned));
             sh->offset = av_malloc_array(sh->num_entry_point_offsets, sizeof(int));
             sh->size = av_malloc_array(sh->num_entry_point_offsets, sizeof(int));
             if (!sh->entry_point_offset || !sh->offset || !sh->size) {
@@ -2441,7 +2441,7 @@ static int hls_slice_data_wpp(HEVCContext *s, const HEVCNAL *nal)
     int *ret = av_malloc_array(s->sh.num_entry_point_offsets + 1, sizeof(int));
     int *arg = av_malloc_array(s->sh.num_entry_point_offsets + 1, sizeof(int));
     int64_t offset;
-    int startheader, cmpt = 0;
+    int64_t startheader, cmpt = 0;
     int i, j, res = 0;
 
     if (!ret || !arg) {

libavcodec/hevc.h

@@ -622,7 +622,7 @@ typedef struct SliceHeader {
 
     unsigned int max_num_merge_cand; ///< 5 - 5_minus_max_num_merge_cand
 
-    int *entry_point_offset;
+    unsigned *entry_point_offset;
     int * offset;
     int * size;
     int num_entry_point_offsets;