[PATCH 5.9 331/391] net/sunrpc: Fix return value for sysctl sunrpc.transports

[Greg Kroah-Hartman]

From: Artur Molchanov <arturmolchanov@xxxxxxxxx>

commit c09f56b8f68d4d536bff518227aea323b835b2ce upstream.

Fix returning value for sysctl sunrpc.transports.
Return error code from sysctl proc_handler function proc_do_xprt instead of number of the written bytes.
Otherwise sysctl returns random garbage for this key.

Since v1:
- Handle negative returned value from memory_read_from_buffer as an error

Signed-off-by: Artur Molchanov <arturmolchanov@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/sunrpc/sysctl.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/net/sunrpc/sysctl.c
+++ b/net/sunrpc/sysctl.c
@@ -70,7 +70,13 @@ static int proc_do_xprt(struct ctl_table
 		return 0;
 	}
 	len = svc_print_xprts(tmpbuf, sizeof(tmpbuf));
-	return memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
+	*lenp = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len);
+
+	if (*lenp < 0) {
+		*lenp = 0;
+		return -EINVAL;
+	}
+	return 0;
 }
 
 static int