queue-4.19/ipv6-flowlabel-fl6_sock_lookup-must-use-atomic_inc_n.patch

   1 From 1355406b8d840e932fae71e38323c9a6566e67ad Mon Sep 17 00:00:00 2001
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Thu, 6 Jun 2019 14:32:34 -0700
   4 Subject: ipv6: flowlabel: fl6_sock_lookup() must use atomic_inc_not_zero
   5
   6 [ Upstream commit 65a3c497c0e965a552008db8bc2653f62bc925a1 ]
   7
   8 Before taking a refcount, make sure the object is not already
   9 scheduled for deletion.
  10
  11 Same fix is needed in ipv6_flowlabel_opt()
  12
  13 Fixes: 18367681a10b ("ipv6 flowlabel: Convert np->ipv6_fl_list to RCU.")
  14 Signed-off-by: Eric Dumazet <edumazet@google.com>
  15 Cc: Willem de Bruijn <willemb@google.com>
  16 Signed-off-by: David S. Miller <davem@davemloft.net>
  17 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  18 ---
  19  net/ipv6/ip6_flowlabel.c | 7 ++++---
  20  1 file changed, 4 insertions(+), 3 deletions(-)
  21
  22 diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
  23 index be5f3d7ceb96..f994f50e1516 100644
  24 --- a/net/ipv6/ip6_flowlabel.c
  25 +++ b/net/ipv6/ip6_flowlabel.c
  26 @@ -254,9 +254,9 @@ struct ip6_flowlabel *fl6_sock_lookup(struct sock *sk, __be32 label)
  27         rcu_read_lock_bh();
  28         for_each_sk_fl_rcu(np, sfl) {
  29                 struct ip6_flowlabel *fl = sfl->fl;
  30 -               if (fl->label == label) {
  31 +
  32 +               if (fl->label == label && atomic_inc_not_zero(&fl->users)) {
  33                         fl->lastuse = jiffies;
  34 -                       atomic_inc(&fl->users);
  35                         rcu_read_unlock_bh();
  36                         return fl;
  37                 }
  38 @@ -622,7 +622,8 @@ int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen)
  39                                                 goto done;
  40                                         }
  41                                         fl1 = sfl->fl;
  42 -                                       atomic_inc(&fl1->users);
  43 +                                       if (!atomic_inc_not_zero(&fl1->users))
  44 +                                               fl1 = NULL;
  45                                         break;
  46                                 }
  47                         }
  48 --
  49 2.20.1
  50