linux-kernel - [PATCH] net: cxgb3_main: Add CAP_NET_ADMIN check to CHELSIO_GET

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Message-Id: <20200124094144.15831-1-mpe@ellerman.id.au>
Date:   Fri, 24 Jan 2020 20:41:44 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, linux-kernel@...r.kernel.org,
        security@...nel.org, ivansprundel@...ctive.com, vishal@...lsio.com
Subject: [PATCH] net: cxgb3_main: Add CAP_NET_ADMIN check to CHELSIO_GET_MEM

The cxgb3 driver for "Chelsio T3-based gigabit and 10Gb Ethernet
adapters" implements a custom ioctl as SIOCCHIOCTL/SIOCDEVPRIVATE in
cxgb_extension_ioctl().

One of the subcommands of the ioctl is CHELSIO_GET_MEM, which appears
to read memory directly out of the adapter and return it to userspace.
It's not entirely clear what the contents of the adapter memory
contains, but the assumption is that it shouldn't be accessible to all
users.

So add a CAP_NET_ADMIN check to the CHELSIO_GET_MEM case. Put it after
the is_offload() check, which matches two of the other subcommands in
the same function which also check for is_offload() and CAP_NET_ADMIN.

Found by Ilja by code inspection, not tested as I don't have the
required hardware.

Reported-by: Ilja Van Sprundel <ivansprundel@...ctive.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
---
 drivers/net/ethernet/chelsio/cxgb3/cxgb3_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/chelsio/cxgb3/cxgb3_main.c b/drivers/net/ethernet/chelsio/cxgb3/cxgb3_main.c
index 58f89f6a040f..97ff8608f0ab 100644
--- a/drivers/net/ethernet/chelsio/cxgb3/cxgb3_main.c
+++ b/drivers/net/ethernet/chelsio/cxgb3/cxgb3_main.c
@@ -2448,6 +2448,8 @@ static int cxgb_extension_ioctl(struct net_device *dev, void __user *useraddr)

 		if (!is_offload(adapter))
 			return -EOPNOTSUPP;
+		if (!capable(CAP_NET_ADMIN))
+			return -EPERM;
 		if (!(adapter->flags & FULL_INIT_DONE))
 			return -EIO;	/* need the memory controllers */
 		if (copy_from_user(&t, useraddr, sizeof(t)))
-- 
2.21.1