[FFmpeg-cvslog] lavc/vvc: Fix slice_idx out-of-bounds memset

[Frank Plowman]

ffmpeg | branch: master | Frank Plowman <post at frankplowman.com> | Mon Feb  5 18:00:05 2024 +0000| [a42f884cd2fafb7aa53bf7b56c20355cd61ca1f5] | committer: Nuo Mi

lavc/vvc: Fix slice_idx out-of-bounds memset

If the number of CTUs reduces between one picture and the next, the
slice_idx table is reduced in size in the frame_context_for_each_tl call
on vvcdec.c:321.  When initialising the slice_idx table on vvcdec.c:325,
the old code uses fc->tab.sz.ctu_count when calculating the table size.
fc->tab.sz.ctu_count holds the old ctu count at this point however, not
being updated to hold the new ctu count until vvcdec.c:342.  This causes
an out-of-bounds write.

Patch fixes the problem by using pps->ctb_count, which was just used
when allocating the table, in place of fc->tab.sz.ctu_count when
initialising the table.

Signed-off-by: Frank Plowman <post at frankplowman.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a42f884cd2fafb7aa53bf7b56c20355cd61ca1f5
---

 libavcodec/vvc/vvcdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/vvc/vvcdec.c b/libavcodec/vvc/vvcdec.c
index 1a050600eb..8163b5ecb6 100644
--- a/libavcodec/vvc/vvcdec.c
+++ b/libavcodec/vvc/vvcdec.c
@@ -322,7 +322,7 @@ static int pic_arrays_init(VVCContext *s, VVCFrameContext *fc)
     if (ret < 0)
         return ret;
 
-    memset(fc->tab.slice_idx, -1, sizeof(*fc->tab.slice_idx) * fc->tab.sz.ctu_count);
+    memset(fc->tab.slice_idx, -1, sizeof(*fc->tab.slice_idx) * ctu_count);
 
     if (fc->tab.sz.ctu_count != ctu_count) {
         ff_refstruct_pool_uninit(&fc->rpl_tab_pool);