Merge commit '7ebdffc3'

* commit '7ebdffc3':
  dxv: Check to make sure we don't overrun buffers on corrupt inputs
Merged-by: Clément Bœsch <u@pkh.me>

libavcodec/dxv.c

@@ -133,7 +133,7 @@ static int dxv_decompress_dxt1(AVCodecContext *avctx)
     AV_WL32(ctx->tex_data + 4, bytestream2_get_le32(gbc));
 
     /* Process input until the whole texture has been filled */
-    while (pos < ctx->tex_size / 4) {
+    while (pos + 2 <= ctx->tex_size / 4) {
         CHECKPOINT(2);
 
         /* Copy two elements from a previous offset or from the input buffer */
@@ -186,7 +186,7 @@ static int dxv_decompress_dxt5(AVCodecContext *avctx)
     AV_WL32(ctx->tex_data + 12, bytestream2_get_le32(gbc));
 
     /* Process input until the whole texture has been filled */
-    while (pos < ctx->tex_size / 4) {
+    while (pos + 2 <= ctx->tex_size / 4) {
         if (run) {
             run--;
 
@@ -215,7 +215,7 @@ static int dxv_decompress_dxt5(AVCodecContext *avctx)
                         check += probe;
                     } while (probe == 0xFFFF);
                 }
-                while (check && pos < ctx->tex_size / 4) {
+                while (check && pos + 4 <= ctx->tex_size / 4) {
                     prev = AV_RL32(ctx->tex_data + 4 * (pos - 4));
                     AV_WL32(ctx->tex_data + 4 * pos, prev);
                     pos++;
@@ -260,10 +260,8 @@ static int dxv_decompress_dxt5(AVCodecContext *avctx)
             case 2:
                 /* Copy two dwords from a previous index */
                 idx = 8 + bytestream2_get_le16(gbc);
-                if (idx > pos) {
-                    av_log(avctx, AV_LOG_ERROR, "idx %d > %d\n", idx, pos);
+                if (idx > pos || (unsigned int)(pos - idx) + 2 > ctx->tex_size / 4)
                     return AVERROR_INVALIDDATA;
-                }
                 prev = AV_RL32(ctx->tex_data + 4 * (pos - idx));
                 AV_WL32(ctx->tex_data + 4 * pos, prev);
                 pos++;
@@ -286,9 +284,13 @@ static int dxv_decompress_dxt5(AVCodecContext *avctx)
         }
 
         CHECKPOINT(4);
+        if (pos + 2 > ctx->tex_size / 4)
+            return AVERROR_INVALIDDATA;
 
         /* Copy two elements from a previous offset or from the input buffer */
         if (op) {
+            if (idx > pos || (unsigned int)(pos - idx) + 2 > ctx->tex_size / 4)
+                return AVERROR_INVALIDDATA;
             prev = AV_RL32(ctx->tex_data + 4 * (pos - idx));
             AV_WL32(ctx->tex_data + 4 * pos, prev);
             pos++;
@@ -299,6 +301,8 @@ static int dxv_decompress_dxt5(AVCodecContext *avctx)
         } else {
             CHECKPOINT(4);
 
+            if (op && (idx > pos || (unsigned int)(pos - idx) + 2 > ctx->tex_size / 4))
+                return AVERROR_INVALIDDATA;
             if (op)
                 prev = AV_RL32(ctx->tex_data + 4 * (pos - idx));
             else