linux-kernel - [PATCH] netlink: do not set cb_running if dump's start() errs

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>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20171009115648.25989-1-Jason@zx2c4.com>
Date:   Mon,  9 Oct 2017 13:56:48 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     johannes@...solutions.net, davem@...emloft.net,
        Netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] netlink: do not set cb_running if dump's start() errs

It turns out that multiple places can call netlink_dump(), which means
it's still possible to dereference partially initialized values in
dump() that were the result of a faulty returned start().

This fixes the issue by calling start() _before_ setting cb_running to
true, so that there's no chance at all of hitting the dump() function
through any indirect paths.

In testing this with several different pieces of tricky code to trigger
these issues, this commit fixes all avenues that I'm aware of.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Cc: Johannes Berg <johannes@...solutions.net>
---
 net/netlink/af_netlink.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 94c11cf0459d..f34750691c5c 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2266,16 +2266,17 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 	cb->min_dump_alloc = control->min_dump_alloc;
 	cb->skb = skb;
 
+	if (cb->start) {
+		ret = cb->start(cb);
+		if (ret)
+			goto error_unlock;
+	}
+
 	nlk->cb_running = true;
 
 	mutex_unlock(nlk->cb_mutex);
 
-	ret = 0;
-	if (cb->start)
-		ret = cb->start(cb);
-
-	if (!ret)
-		ret = netlink_dump(sk);
+	ret = netlink_dump(sk);
 
 	sock_put(sk);
 
-- 
2.14.2