firmware: meson-sm: Check for buffer output size

After the data is read by the secure monitor driver it is being copied
in the output buffer checking only the size of the bounce buffer but not
the size of the output buffer.

Fix this in the secure monitor driver slightly changing the API. Fix
also the efuse driver that it is the only driver using this API to not
break bisectability.

Signed-off-by: Carlo Caione <[e-mail]>
Acked-by: Srinivas Kandagatla <[e-mail]> # for nvmem
Acked-by: Mark Rutland <[e-mail]>
Signed-off-by: Kevin Hilman <[e-mail]>

drivers/firmware/meson/meson_sm.c

···
  * meson_sm_call_read - retrieve data from secure-monitor
  *
  * @buffer:	Buffer to store the retrieved data
+ * @bsize:	Size of the buffer
  * @cmd_index:	Index of the SMC32 function ID
  * @arg0:	SMC32 Argument 0
  * @arg1:	SMC32 Argument 1
···
  *
  * Return:	size of read data on success, a negative value on error
  */
-int meson_sm_call_read(void *buffer, unsigned int cmd_index, u32 arg0,
-		       u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+int meson_sm_call_read(void *buffer, unsigned int bsize, unsigned int cmd_index,
+		       u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
 {
 	u32 size;
 
···
 	if (!fw.chip->cmd_shmem_out_base)
 		return -EINVAL;
 
+	if (bsize > fw.chip->shmem_size)
+		return -EINVAL;
+
 	if (meson_sm_call(cmd_index, &size, arg0, arg1, arg2, arg3, arg4) < 0)
 		return -EINVAL;
 
-	if (!size || size > fw.chip->shmem_size)
+	if (!size || size > bsize)
 		return -EINVAL;
 
 	if (buffer)

drivers/nvmem/meson-efuse.c

···
 	u8 *buf = val;
 	int ret;
 
-	ret = meson_sm_call_read(buf, SM_EFUSE_READ, offset,
+	ret = meson_sm_call_read(buf, bytes, SM_EFUSE_READ, offset,
 				 bytes, 0, 0, 0);
 	if (ret < 0)
 		return ret;

include/linux/firmware/meson/meson_sm.h

···
 		  u32 arg2, u32 arg3, u32 arg4);
 int meson_sm_call_write(void *buffer, unsigned int b_size, unsigned int cmd_index,
 			u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4);
-int meson_sm_call_read(void *buffer, unsigned int cmd_index, u32 arg0, u32 arg1,
-		       u32 arg2, u32 arg3, u32 arg4);
+int meson_sm_call_read(void *buffer, unsigned int bsize, unsigned int cmd_index,
+		       u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4);
 
 #endif /* _MESON_SM_FW_H_ */