[RFC v1 2/6] pseries/papr-hvpipe: Fix the usage of copy_to_user()

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

copy_to_user() return bytes_not_copied to the user buffer. If there was
an error writing bytes into the user buffer, i.e. if copy_to_user
returns a non-zero value, then we simply return -EFAULT from the
->read() call.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/platforms/pseries/papr-hvpipe.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
index ef10f5a5a4fa..fffebbae113c 100644
--- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
+++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
@@ -206,10 +206,11 @@ static int hvpipe_rtas_recv_msg(char __user *buf, int size)
 					bytes_written, size);
 				bytes_written = size;
 			}
-			ret = copy_to_user(buf,
+			if (copy_to_user(buf,
 					rtas_work_area_raw_buf(work_area),
-					bytes_written);
-			if (!ret)
+					bytes_written))
+				ret = -EFAULT;
+			else
 				ret = bytes_written;
 		}
 	} else {
@@ -376,7 +377,7 @@ static ssize_t papr_hvpipe_handle_read(struct file *file,
 
 	ret = copy_to_user(buf, &hdr, HVPIPE_HDR_LEN);
 	if (ret)
-		return ret;
+		return -EFAULT;
 
 	/*
 	 * Message event has payload, so get the payload with
-- 
2.39.5