releases/4.4.177/ip6mr-do-not-call-__ip6_inc_stats-from-preemptible-context.patch

   1 From foo@baz Fri Mar  8 10:00:48 CET 2019
   2 From: Ido Schimmel <idosch@mellanox.com>
   3 Date: Sun, 3 Mar 2019 07:34:57 +0000
   4 Subject: ip6mr: Do not call __IP6_INC_STATS() from preemptible context
   5
   6 From: Ido Schimmel <idosch@mellanox.com>
   7
   8 [ Upstream commit 87c11f1ddbbad38ad8bad47af133a8208985fbdf ]
   9
  10 Similar to commit 44f49dd8b5a6 ("ipmr: fix possible race resulting from
  11 improper usage of IP_INC_STATS_BH() in preemptible context."), we cannot
  12 assume preemption is disabled when incrementing the counter and
  13 accessing a per-CPU variable.
  14
  15 Preemption can be enabled when we add a route in process context that
  16 corresponds to packets stored in the unresolved queue, which are then
  17 forwarded using this route [1].
  18
  19 Fix this by using IP6_INC_STATS() which takes care of disabling
  20 preemption on architectures where it is needed.
  21
  22 [1]
  23 [  157.451447] BUG: using __this_cpu_add() in preemptible [00000000] code: smcrouted/2314
  24 [  157.460409] caller is ip6mr_forward2+0x73e/0x10e0
  25 [  157.460434] CPU: 3 PID: 2314 Comm: smcrouted Not tainted 5.0.0-rc7-custom-03635-g22f2712113f1 #1336
  26 [  157.460449] Hardware name: Mellanox Technologies Ltd. MSN2100-CB2FO/SA001017, BIOS 5.6.5 06/07/2016
  27 [  157.460461] Call Trace:
  28 [  157.460486]  dump_stack+0xf9/0x1be
  29 [  157.460553]  check_preemption_disabled+0x1d6/0x200
  30 [  157.460576]  ip6mr_forward2+0x73e/0x10e0
  31 [  157.460705]  ip6_mr_forward+0x9a0/0x1510
  32 [  157.460771]  ip6mr_mfc_add+0x16b3/0x1e00
  33 [  157.461155]  ip6_mroute_setsockopt+0x3cb/0x13c0
  34 [  157.461384]  do_ipv6_setsockopt.isra.8+0x348/0x4060
  35 [  157.462013]  ipv6_setsockopt+0x90/0x110
  36 [  157.462036]  rawv6_setsockopt+0x4a/0x120
  37 [  157.462058]  __sys_setsockopt+0x16b/0x340
  38 [  157.462198]  __x64_sys_setsockopt+0xbf/0x160
  39 [  157.462220]  do_syscall_64+0x14d/0x610
  40 [  157.462349]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  41
  42 Fixes: 0912ea38de61 ("[IPV6] MROUTE: Add stats in multicast routing module method ip6_mr_forward().")
  43 Signed-off-by: Ido Schimmel <idosch@mellanox.com>
  44 Reported-by: Amit Cohen <amitc@mellanox.com>
  45 Signed-off-by: David S. Miller <davem@davemloft.net>
  46 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  47 ---
  48  net/ipv6/ip6mr.c |    8 ++++----
  49  1 file changed, 4 insertions(+), 4 deletions(-)
  50
  51 --- a/net/ipv6/ip6mr.c
  52 +++ b/net/ipv6/ip6mr.c
  53 @@ -1990,10 +1990,10 @@ int ip6mr_compat_ioctl(struct sock *sk,
  54
  55  static inline int ip6mr_forward2_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  56  {
  57 -       IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)),
  58 -                        IPSTATS_MIB_OUTFORWDATAGRAMS);
  59 -       IP6_ADD_STATS_BH(net, ip6_dst_idev(skb_dst(skb)),
  60 -                        IPSTATS_MIB_OUTOCTETS, skb->len);
  61 +       IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
  62 +                     IPSTATS_MIB_OUTFORWDATAGRAMS);
  63 +       IP6_ADD_STATS(net, ip6_dst_idev(skb_dst(skb)),
  64 +                     IPSTATS_MIB_OUTOCTETS, skb->len);
  65         return dst_output(net, sk, skb);
  66  }
  67