3.16.52-rc1 review patch. If anyone has any objections, please let me know.
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From: Ben Hutchings ben@decadent.org.uk
commit 1137b5e2529a8f5ca8ee709288ecba3e68044df2 upstream.
This is a fix for CVE-2017-16939 suitable for older stable branches. The upstream fix is commit 1137b5e2529a8f5ca8ee709288ecba3e68044df2, from which the following explanation is taken:
An independent security researcher, Mohamed Ghannam, has reported this vulnerability to Beyond Security's SecuriTeam Secure Disclosure program.
The xfrm_dump_policy_done function expects xfrm_dump_policy to have been called at least once or it will crash. This can be triggered if a dump fails because the target socket's receive buffer is full.
It was not possible to define a 'start' callback for netlink dumps until Linux 4.5, so instead add a check for the initialisation flag in the 'done' callback.
Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1570,7 +1570,8 @@ static int xfrm_dump_policy_done(struct struct xfrm_policy_walk *walk = (struct xfrm_policy_walk *) &cb->args[1]; struct net *net = sock_net(cb->skb->sk);
- xfrm_policy_walk_done(walk, net); + if (cb->args[0]) + xfrm_policy_walk_done(walk, net); return 0; }