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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Artur Molchanov <arturmolchanov@gmail.com>,
        "J. Bruce Fields" <bfields@redhat.com>
Subject: [PATCH 5.9 331/391] net/sunrpc: Fix return value for sysctl sunrpc.transports
Date:   Tue,  3 Nov 2020 21:36:22 +0100
Message-Id: <20201103203409.457535281@linuxfoundation.org>
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From: Artur Molchanov <arturmolchanov@gmail.com>

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@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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