netdev - [PATCH 3.11 v3] genetlink: fix family dump race

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:	Tue, 13 Aug 2013 09:04:05 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	netdev@...r.kernel.org
Cc:	linux-wireless@...r.kernel.org,
	Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 3.11 v3] genetlink: fix family dump race

From: Johannes Berg <johannes.berg@...el.com>

When dumping generic netlink families, only the first dump call
is locked with genl_lock(), which protects the list of families,
and thus subsequent calls can access the data without locking,
racing against family addition/removal. This can cause a crash.
Fix it - the locking needs to be conditional because the first
time around it's already locked.

A similar bug was reported to me on an old kernel (3.4.47) but
the exact scenario that happened there is no longer possible,
on those kernels the first round wasn't locked either. Looking
at the current code I found the race described above, which had
also existed on the old kernel.

Cc: stable@...r.kernel.org
Reported-by: Andrei Otcheretianski <andrei.otcheretianski@...el.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 net/netlink/genetlink.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 2fd6dbe..6b6a03a 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -789,6 +789,10 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 	struct net *net = sock_net(skb->sk);
 	int chains_to_skip = cb->args[0];
 	int fams_to_skip = cb->args[1];
+	bool need_locking = chains_to_skip || fams_to_skip;
+
+	if (need_locking)
+		genl_lock();

 	for (i = chains_to_skip; i < GENL_FAM_TAB_SIZE; i++) {
 		n = 0;
@@ -810,6 +814,9 @@ errout:
 	cb->args[0] = i;
 	cb->args[1] = n;

+	if (need_locking)
+		genl_unlock();
+
 	return skb->len;
 }

-- 
1.8.0

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html