[fix][dfs] elmfat磁盘操作设备指针判空

Author: Unbear-Hz

components/dfs/dfs_v1/filesystems/elmfat/dfs_elm.c

@@ -908,6 +908,9 @@ DRESULT disk_read(BYTE drv, BYTE *buff, DWORD sector, UINT count)
     rt_size_t result;
     rt_device_t device = disk[drv];
 
+    if (device == RT_NULL)
+        return RES_ERROR;
+
     result = rt_device_read(device, sector, buff, count);
     if (result == count)
     {
@@ -923,6 +926,9 @@ DRESULT disk_write(BYTE drv, const BYTE *buff, DWORD sector, UINT count)
     rt_size_t result;
     rt_device_t device = disk[drv];
 
+    if (device == RT_NULL)
+        return RES_ERROR;
+
     result = rt_device_write(device, sector, buff, count);
     if (result == count)
     {

components/dfs/dfs_v2/filesystems/elmfat/dfs_elm.c

@@ -1146,6 +1146,9 @@ DRESULT disk_read(BYTE drv, BYTE *buff, DWORD sector, UINT count)
     rt_size_t result;
     rt_device_t device = disk[drv];
 
+    if (device == RT_NULL)
+        return RES_ERROR;
+
     result = rt_device_read(device, sector, buff, count);
     if (result == count)
     {
@@ -1161,6 +1164,9 @@ DRESULT disk_write(BYTE drv, const BYTE *buff, DWORD sector, UINT count)
     rt_size_t result;
     rt_device_t device = disk[drv];
 
+    if (device == RT_NULL)
+        return RES_ERROR;
+
     result = rt_device_write(device, sector, buff, count);
     if (result == count)
     {