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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,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 064/235] powerpc/powernv: opal_put_chars partial write fix
Date:   Mon, 24 Sep 2018 13:50:50 +0200
Message-Id: <20180924113111.589473383@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Piggin <npiggin@gmail.com>

[ Upstream commit bd90284cc6c1c9e8e48c8eadd0c79574fcce0b81 ]

The intention here is to consume and discard the remaining buffer
upon error. This works if there has not been a previous partial write.
If there has been, then total_len is no longer total number of bytes
to copy. total_len is always "bytes left to copy", so it should be
added to written bytes.

This code may not be exercised any more if partial writes will not be
hit, but this is a small bugfix before a larger change.

Reviewed-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/powerpc/platforms/powernv/opal.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -388,7 +388,7 @@ int opal_put_chars(uint32_t vtermno, con
 		/* Closed or other error drop */
 		if (rc != OPAL_SUCCESS && rc != OPAL_BUSY &&
 		    rc != OPAL_BUSY_EVENT) {
-			written = total_len;
+			written += total_len;
 			break;
 		}
 		if (rc == OPAL_SUCCESS) {