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[PATCH 3.18 11/36] ipv6: fix calling in6_ifa_hold incorrectly for dad work

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3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@gmail.com>


[ Upstream commit f8a894b218138888542a5058d0e902378fd0d4ec ]

Now when starting the dad work in addrconf_mod_dad_work, if the dad work
is idle and queued, it needs to hold ifa.

The problem is there's one gap in [1], during which if the pending dad work
is removed elsewhere. It will miss to hold ifa, but the dad word is still
idea and queue.

        if (!delayed_work_pending(&ifp->dad_work))
                in6_ifa_hold(ifp);
                    <--------------[1]
        mod_delayed_work(addrconf_wq, &ifp->dad_work, delay);

An use-after-free issue can be caused by this.

Chen Wei found this issue when WARN_ON(!hlist_unhashed(&ifp->addr_lst)) in
net6_ifa_finish_destroy was hit because of it.

As Hannes' suggestion, this patch is to fix it by holding ifa first in
addrconf_mod_dad_work, then calling mod_delayed_work and putting ifa if
the dad_work is already in queue.

Note that this patch did not choose to fix it with:

  if (!mod_delayed_work(delay))
          in6_ifa_hold(ifp);

As with it, when delay == 0, dad_work would be scheduled immediately, all
addrconf_mod_dad_work(0) callings had to be moved under ifp->lock.

Reported-by: Wei Chen <weichen@redhat.com>
Suggested-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/addrconf.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -269,9 +269,9 @@ static void addrconf_mod_rs_timer(struct
 static void addrconf_mod_dad_work(struct inet6_ifaddr *ifp,
 				   unsigned long delay)
 {
-	if (!delayed_work_pending(&ifp->dad_work))
-		in6_ifa_hold(ifp);
-	mod_delayed_work(addrconf_wq, &ifp->dad_work, delay);
+	in6_ifa_hold(ifp);
+	if (mod_delayed_work(addrconf_wq, &ifp->dad_work, delay))
+		in6_ifa_put(ifp);
 }
 
 static int snmp6_alloc_dev(struct inet6_dev *idev)

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[PATCH 3.18 00/36] 3.18.60-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 15:40 +0200
  [PATCH 3.18 15/36] arm64: cpuinfo: Missing NULL terminator in compat_hwcap_str Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 15:40 +0200
  [PATCH 3.18 34/36] cpufreq: s3c2416: double free on driver init error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 15:40 +0200
  [PATCH 3.18 18/36] MIPS: Fix IRQ tracing & lockdep when rescheduling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 15:40 +0200
  [PATCH 3.18 25/36] net: korina: Fix NAPI versus resources freeing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 15:40 +0200
  Re: [PATCH 3.18 14/36] NFSv4: fix a reference leak caused WARNING  messages Trond Myklebust <trondmy@primarydata.com> - 2017-07-03 16:40 +0200
    Re: [PATCH 3.18 14/36] NFSv4: fix a reference leak caused WARNING  messages "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org> - 2017-07-03 17:10 +0200
  [PATCH 3.18 28/36] xfrm: NULL dereference on allocation failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 31/36] ARM: 8685/1: ensure memblock-limit is pmd-aligned Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 11/36] ipv6: fix calling in6_ifa_hold incorrectly for dad work Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 32/36] iommu/vt-d: Dont over-free page table directories Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 06/36] decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 27/36] xfrm: fix stack access out of bounds with CONFIG_XFRM_SUB_POLICY Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 05/36] net: dont call strlen on non-terminated string in dev_set_alias() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 29/36] xfrm: Oops on error in pfkey_msg2xfrm_state() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 07/36] Fix an intermittent pr_emerg warning about lo becoming free. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 20/36] drm/vmwgfx: Free hash table allocated by cmdbuf managed res mgr Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 16/36] MIPS: Avoid accidental raw backtrace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 14/36] NFSv4: fix a reference leak caused WARNING messages Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 08/36] net: caif: Fix a sleep-in-atomic bug in cfpkt_create_pfx Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 30/36] watchdog: bcm281xx: Fix use of uninitialized spinlock. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  [PATCH 3.18 17/36] MIPS: pm-cps: Drop manual cache-line alignment of ready_count Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-03 17:20 +0200
  Re: [PATCH 3.18 00/36] 3.18.60-stable review Guenter Roeck <linux@roeck-us.net> - 2017-07-03 21:40 +0200

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