netdev - [PATCH net-next 2/3] net: bridge: fix ioctl old

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Message-Id: <20210805082903.711396-3-razor@blackwall.org>
Date:   Thu,  5 Aug 2021 11:29:02 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     netdev@...r.kernel.org
Cc:     roopa@...dia.com, arnd@...db.de, bridge@...ts.linux-foundation.org,
        Nikolay Aleksandrov <nikolay@...dia.com>
Subject: [PATCH net-next 2/3] net: bridge: fix ioctl old_deviceless bridge argument

From: Nikolay Aleksandrov <nikolay@...dia.com>

Commit ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl")
changed the source of the argument copy in bridge's old_deviceless() from
args[1] (user ptr to device name) to uarg (ptr to ioctl arguments) causing
wrong device name to be used.

Example (broken, bridge exists but is up):
$ brctl delbr bridge
bridge bridge doesn't exist; can't delete it

Example (working):
$ brctl delbr bridge
bridge bridge is still up; can't delete it

Fixes: ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl")
Signed-off-by: Nikolay Aleksandrov <nikolay@...dia.com>
---
 net/bridge/br_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 2f848de3e755..793b0db9d9a3 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -351,7 +351,7 @@ static int old_deviceless(struct net *net, void __user *uarg)
 		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 			return -EPERM;
 
-		if (copy_from_user(buf, uarg, IFNAMSIZ))
+		if (copy_from_user(buf, (void __user *)args[1], IFNAMSIZ))
 			return -EFAULT;
 
 		buf[IFNAMSIZ-1] = 0;
-- 
2.31.1