avfilter/af_afir: fix possible array read-overflow

libavfilter/af_afir.c

@@ -222,8 +222,8 @@ static int init_segment(AVFilterContext *ctx, AudioFIRSegment *seg, int selir,
 
     seg->fft_length    = (part_size + 1) * 2;
     seg->part_size     = part_size;
-    seg->block_size    = FFALIGN(seg->fft_length, cpu_align);
     seg->coeff_size    = FFALIGN(seg->part_size + 1, cpu_align);
+    seg->block_size    = FFMAX(seg->coeff_size * 2, FFALIGN(seg->fft_length, cpu_align));
     seg->nb_partitions = nb_partitions;
     seg->input_size    = offset + s->min_part_size;
     seg->input_offset  = offset;