Patch "genetlink: fix counting regression on ctrl_dumpfamily()" has been added to the 4.10-stable tree

Patch "genetlink: fix counting regression on ctrl_dumpfamily()" has been added to the 4.10-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    genetlink: fix counting regression on ctrl_dumpfamily()

to the 4.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     genetlink-fix-counting-regression-on-ctrl_dumpfamily.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Mar 27 18:18:08 CEST 2017
From: Stanislaw Gruszka <sgruszka@redhat.com>
Date: Wed, 22 Mar 2017 16:08:33 +0100
Subject: genetlink: fix counting regression on ctrl_dumpfamily()

From: Stanislaw Gruszka <sgruszka@redhat.com>


[ Upstream commit 1d2a6a5e4bf2921531071fcff8538623dce74efa ]

Commit 2ae0f17df1cd ("genetlink: use idr to track families") replaced

	if (++n < fams_to_skip)
		continue;
into:

	if (n++ < fams_to_skip)
		continue;

This subtle change cause that on retry ctrl_dumpfamily() call we omit
one family that failed to do ctrl_fill_info() on previous call, because
cb->args[0] = n number counts also family that failed to do
ctrl_fill_info().

Patch fixes the problem and avoid confusion in the future just decrease
n counter when ctrl_fill_info() fail.

User visible problem caused by this bug is failure to get access to
some genetlink family i.e. nl80211. However problem is reproducible
only if number of registered genetlink families is big enough to
cause second call of ctrl_dumpfamily().

Cc: Xose Vazquez Perez <xose.vazquez@gmail.com>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Johannes Berg <johannes@sipsolutions.net>
Fixes: 2ae0f17df1cd ("genetlink: use idr to track families")
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/netlink/genetlink.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -783,8 +783,10 @@ static int ctrl_dumpfamily(struct sk_buf
 
 		if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).portid,
 				   cb->nlh->nlmsg_seq, NLM_F_MULTI,
-				   skb, CTRL_CMD_NEWFAMILY) < 0)
+				   skb, CTRL_CMD_NEWFAMILY) < 0) {
+			n--;
 			break;
+		}
 	}
 
 	cb->args[0] = n;


Patches currently in stable-queue which might be from sgruszka@redhat.com are

queue-4.10/genetlink-fix-counting-regression-on-ctrl_dumpfamily.patch