misc: fastrpc: fix use-after-free of fastrpc_user in workqueue context (#594)

misc: fastrpc: fix use-after-free of fastrpc_user in workqueue context

Author: sgaud-quic

drivers/misc/fastrpc.c

@@ -502,9 +502,30 @@ static void fastrpc_channel_ctx_put(struct fastrpc_channel_ctx *cctx)
 	kref_put(&cctx->refcount, fastrpc_channel_ctx_free);
 }
 
+static void fastrpc_context_put(struct fastrpc_invoke_ctx *ctx);
+
 static void fastrpc_user_free(struct kref *ref)
 {
 	struct fastrpc_user *fl = container_of(ref, struct fastrpc_user, refcount);
+	struct fastrpc_invoke_ctx *ctx, *n;
+	struct fastrpc_map *map, *m;
+	struct fastrpc_buf *buf, *b;
+
+	if (fl->init_mem)
+		fastrpc_buf_free(fl->init_mem);
+
+	list_for_each_entry_safe(ctx, n, &fl->pending, node) {
+		list_del(&ctx->node);
+		fastrpc_context_put(ctx);
+	}
+
+	list_for_each_entry_safe(map, m, &fl->maps, node)
+		fastrpc_map_put(map);
+
+	list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
+		list_del(&buf->node);
+		fastrpc_buf_free(buf);
+	}
 
 	fastrpc_channel_ctx_put(fl->cctx);
 	mutex_destroy(&fl->mutex);
@@ -1655,9 +1676,6 @@ static int fastrpc_device_release(struct inode *inode, struct file *file)
 {
 	struct fastrpc_user *fl = (struct fastrpc_user *)file->private_data;
 	struct fastrpc_channel_ctx *cctx = fl->cctx;
-	struct fastrpc_invoke_ctx *ctx, *n;
-	struct fastrpc_map *map, *m;
-	struct fastrpc_buf *buf, *b;
 	unsigned long flags;
 
 	fastrpc_release_current_dsp_process(fl);
@@ -1666,21 +1684,6 @@ static int fastrpc_device_release(struct inode *inode, struct file *file)
 	list_del(&fl->user);
 	spin_unlock_irqrestore(&cctx->lock, flags);
 
-	fastrpc_buf_free(fl->init_mem);
-
-	list_for_each_entry_safe(ctx, n, &fl->pending, node) {
-		list_del(&ctx->node);
-		fastrpc_context_put(ctx);
-	}
-
-	list_for_each_entry_safe(map, m, &fl->maps, node)
-		fastrpc_map_put(map);
-
-	list_for_each_entry_safe(buf, b, &fl->mmaps, node) {
-		list_del(&buf->node);
-		fastrpc_buf_free(buf);
-	}
-
 	fastrpc_session_free(cctx, fl->sctx);
 	file->private_data = NULL;
 	/* Release the reference taken in fastrpc_device_open */