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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
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