--- /dev/null
+From 6df0d3e2916c223dbe4262bf1b876dff1cb3f980 Mon Sep 17 00:00:00 2001
+From: Michael Niedermayer <michaelni@gmx.at>
+Date: Wed, 12 Dec 2012 12:28:45 +0100
+Subject: [PATCH] alsdec: check block length
+
+Upstream-Status: Backport
+
+Commit 6df0d3e2916c223dbe4262bf1b876dff1cb3f980 release/1.0
+
+Fix writing over the end
+
+Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
+Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
+(cherry picked from commit 0ceca269b66ec12a23bf0907bd2c220513cdbf16)
+
+Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
+---
+ libavcodec/alsdec.c | 10 ++++++++--
+ 1 file changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
+index 46dd0b4..1095b01 100644
+--- a/gst-libs/ext/libav/libavcodec/alsdec.c
++++ b/gst-libs/ext/libav/libavcodec/alsdec.c
+@@ -552,12 +552,15 @@ static void get_block_sizes(ALSDecContext *ctx, unsigned int *div_blocks,
+
+ /** Read the block data for a constant block
+ */
+-static void read_const_block_data(ALSDecContext *ctx, ALSBlockData *bd)
++static int read_const_block_data(ALSDecContext *ctx, ALSBlockData *bd)
+ {
+ ALSSpecificConfig *sconf = &ctx->sconf;
+ AVCodecContext *avctx = ctx->avctx;
+ GetBitContext *gb = &ctx->gb;
+
++ if (bd->block_length <= 0)
++ return -1;
++
+ *bd->raw_samples = 0;
+ *bd->const_block = get_bits1(gb); // 1 = constant value, 0 = zero block (silence)
+ bd->js_blocks = get_bits1(gb);
+@@ -572,6 +575,8 @@ static void read_const_block_data(ALSDecContext *ctx, ALSBlockData *bd)
+
+ // ensure constant block decoding by reusing this field
+ *bd->const_block = 1;
++
++ return 0;
+ }
+
+
+@@ -971,7 +976,8 @@ static int read_block(ALSDecContext *ctx, ALSBlockData *bd)
+ if (read_var_block_data(ctx, bd))
+ return -1;
+ } else {
+- read_const_block_data(ctx, bd);
++ if (read_const_block_data(ctx, bd) < 0)
++ return -1;
+ }
+
+ return 0;
+--
