netdev - [PATCH net] mlx4: Fix information leak on failure to read module EEPROM

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Message-ID: <20200517172053.GA734488@decadent.org.uk>
Date:   Sun, 17 May 2020 18:20:53 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     Tariq Toukan <tariqt@...lanox.com>
Cc:     960702@...s.debian.org, netdev@...r.kernel.org
Subject: [PATCH net] mlx4: Fix information leak on failure to read module
 EEPROM

mlx4_en_get_module_eeprom() returns 0 even if it fails.  This results
in copying an uninitialised (or partly initialised) buffer back to
user-space.

Change it so that:

* In the special case that the DOM turns out not to be readable, the
  remaining part of the buffer is cleared.  This should avoid a
  regression when reading modules with this problem.

* In other error cases, the error code is propagated.

Reported-by: Yannis Aribaud <bugs@...ell.net>
References: https://bugs.debian.org/960702
Fixes: 7202da8b7f71 ("ethtool, net/mlx4_en: Cable info, get_module_info/...")
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
This is compile-tested only.  It should go to stable, if it is a
correct fix.

Ben.

 drivers/net/ethernet/mellanox/mlx4/en_ethtool.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c b/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
index 8a5ea2543670..6edc3177af1c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
@@ -2078,14 +2078,17 @@ static int mlx4_en_get_module_eeprom(struct net_device *dev,
 		ret = mlx4_get_module_info(mdev->dev, priv->port,
 					   offset, ee->len - i, data + i);
 
-		if (!ret) /* Done reading */
+		if (!ret) {
+			/* DOM was not readable after all */
+			memset(data + i, 0, ee->len - i);
 			return 0;
+		}
 
 		if (ret < 0) {
 			en_err(priv,
 			       "mlx4_get_module_info i(%d) offset(%d) bytes_to_read(%d) - FAILED (0x%x)\n",
 			       i, offset, ee->len - i, ret);
-			return 0;
+			return ret;
 		}
 
 		i += ret;

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