[PATCH] powerpc/pseries: papr-hvpipe: Return -EFAULT on copy_to_user() failure

[Alper Ak]

copy_to_user() returns the number of bytes that could not be copied,
not an error code. Currently, hvpipe_rtas_recv_msg() and
papr_hvpipe_handle_read() return this positive value directly on
failure, which userspace interprets as a successful read of that
many bytes.

Return -EFAULT when copy_to_user() fails.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <error27@xxxxxxxxx>
Closes: https://lore.kernel.org/r/202512240028.EKDG3Wu6-lkp@xxxxxxxxx/
Signed-off-by: Alper Ak <alperyasinak1@xxxxxxxxx>
---
 arch/powerpc/platforms/pseries/papr-hvpipe.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
index dd7b668799d9..0dee94c7c887 100644
--- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
+++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
@@ -209,7 +209,9 @@ static int hvpipe_rtas_recv_msg(char __user *buf, int size)
 			ret = copy_to_user(buf,
 					rtas_work_area_raw_buf(work_area),
 					bytes_written);
-			if (!ret)
+			if (ret)
+				ret = -EFAULT;
+			else
 				ret = bytes_written;
 		}
 	} else {
@@ -376,7 +378,7 @@ 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
-- 
2.43.0