v4l2: allocate buffer array separately

The array may be reallocated later on, so it ought to be allocated
separately from its container.

modules/access/v4l2/buffers.c

@@ -87,8 +87,10 @@ static void ReleaseBuffer(block_t *block)
 
     v4l2_munmap(block->p_start, block->i_size);
 
-    if (vlc_popcount(mask) == 1) /* last active buffer? */
+    if (vlc_popcount(mask) == 1) { /* last active buffer? */
+        free(pool->bufs);
         free(pool);
+    }
 }
 
 static const struct vlc_block_callbacks vlc_v4l2_buffer_cbs = {
@@ -167,10 +169,16 @@ struct vlc_v4l2_buffers *StartMmap(vlc_object_t *obj, int fd)
         return NULL;
     }
 
-    pool = malloc(sizeof (*pool) + req.count * sizeof (pool->bufs[0]));
+    pool = malloc(sizeof (*pool));
     if (unlikely(pool == NULL))
         return NULL;
 
+    pool->bufs = calloc(req.count, sizeof (pool->bufs[0]));
+    if (unlikely(pool->bufs == NULL)) {
+        free(pool);
+        return NULL;
+    }
+
     pool->fd = fd;
     pool->inflight = 0;
     pool->count = 0;

modules/access/v4l2/v4l2.h

@@ -45,11 +45,12 @@ struct vlc_v4l2_buffer {
 };
 
 struct vlc_v4l2_buffers {
+    size_t count;
+    struct vlc_v4l2_buffer *bufs;
+
     int fd;
     _Atomic uint32_t inflight;
     vlc_mutex_t lock;
-    size_t count;
-    struct vlc_v4l2_buffer bufs[];
 };
 
 /* v4l2.c */