linux-kernel - [ 37/49] net: fix rtnetlink IFF_PROMISC and IFF

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Message-Id: <20120807222030.184332865@linuxfoundation.org>
Date:	Tue,  7 Aug 2012 15:44:55 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Max Matveev <makc@...hat.com>,
	Jiri Benc <jbenc@...hat.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 37/49] net: fix rtnetlink IFF_PROMISC and IFF_ALLMULTI handling

From: Greg KH <gregkh@...uxfoundation.org>

3.0-stable review patch.  If anyone has any objections, please let me know.

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


From: Jiri Benc <jbenc@...hat.com>

[ Upstream commit b1beb681cba5358f62e6187340660ade226a5fcc ]

When device flags are set using rtnetlink, IFF_PROMISC and IFF_ALLMULTI
flags are handled specially. Function dev_change_flags sets IFF_PROMISC and
IFF_ALLMULTI bits in dev->gflags according to the passed value but
do_setlink passes a result of rtnl_dev_combine_flags which takes those bits
from dev->flags.

This can be easily trigerred by doing:

tcpdump -i eth0 &
ip l s up eth0

ip sets IFF_UP flag in ifi_flags and ifi_change, which is combined with
IFF_PROMISC by rtnl_dev_combine_flags, causing __dev_change_flags to set
IFF_PROMISC in gflags.

Reported-by: Max Matveev <makc@...hat.com>
Signed-off-by: Jiri Benc <jbenc@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/rtnetlink.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -647,6 +647,12 @@ static void set_operstate(struct net_dev
 	}
 }
 
+static unsigned int rtnl_dev_get_flags(const struct net_device *dev)
+{
+	return (dev->flags & ~(IFF_PROMISC | IFF_ALLMULTI)) |
+	       (dev->gflags & (IFF_PROMISC | IFF_ALLMULTI));
+}
+
 static unsigned int rtnl_dev_combine_flags(const struct net_device *dev,
 					   const struct ifinfomsg *ifm)
 {
@@ -655,7 +661,7 @@ static unsigned int rtnl_dev_combine_fla
 	/* bugwards compatibility: ifi_change == 0 is treated as ~0 */
 	if (ifm->ifi_change)
 		flags = (flags & ifm->ifi_change) |
-			(dev->flags & ~ifm->ifi_change);
+			(rtnl_dev_get_flags(dev) & ~ifm->ifi_change);
 
 	return flags;
 }


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