smacker: Check get_vlc() return values.

Fixes out of array reads

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/smacker.c

@@ -672,11 +672,19 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
                     res = get_vlc2(&gb, vlc[2].table, SMKTREE_BITS, 3);
                 else
                     res = 0;
+                if (res < 0) {
+                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 val  = h[2].values[res];
                 if(vlc[3].table)
                     res = get_vlc2(&gb, vlc[3].table, SMKTREE_BITS, 3);
                 else
                     res = 0;
+                if (res < 0) {
+                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 val |= h[3].values[res] << 8;
                 pred[1] += sign_extend(val, 16);
                 *samples++ = av_clip_int16(pred[1]);
@@ -685,11 +693,19 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
                     res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3);
                 else
                     res = 0;
+                if (res < 0) {
+                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 val  = h[0].values[res];
                 if(vlc[1].table)
                     res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3);
                 else
                     res = 0;
+                if (res < 0) {
+                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 val |= h[1].values[res] << 8;
                 pred[0] += sign_extend(val, 16);
                 *samples++ = av_clip_int16(pred[0]);
@@ -708,6 +724,10 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
                     res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3);
                 else
                     res = 0;
+                if (res < 0) {
+                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 pred[1] += sign_extend(h[1].values[res], 8);
                 *samples8++ = av_clip_uint8(pred[1]);
             } else {
@@ -715,6 +735,10 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data,
                     res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3);
                 else
                     res = 0;
+                if (res < 0) {
+                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 pred[0] += sign_extend(h[0].values[res], 8);
                 *samples8++ = av_clip_uint8(pred[0]);
             }