queue-4.19/ipv6-fix-races-in-ip6_dst_destroy.patch

   1 From foo@baz Sat 04 May 2019 09:23:44 AM CEST
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Sun, 28 Apr 2019 12:22:25 -0700
   4 Subject: ipv6: fix races in ip6_dst_destroy()
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8 [ Upstream commit 0e2338749192ce0e52e7174c5352f627632f478a ]
   9
  10 We had many syzbot reports that seem to be caused by use-after-free
  11 of struct fib6_info.
  12
  13 ip6_dst_destroy(), fib6_drop_pcpu_from() and rt6_remove_exception()
  14 are writers vs rt->from, and use non consistent synchronization among
  15 themselves.
  16
  17 Switching to xchg() will solve the issues with no possible
  18 lockdep issues.
  19
  20 BUG: KASAN: user-memory-access in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:747 [inline]
  21 BUG: KASAN: user-memory-access in fib6_info_release include/net/ip6_fib.h:294 [inline]
  22 BUG: KASAN: user-memory-access in fib6_info_release include/net/ip6_fib.h:292 [inline]
  23 BUG: KASAN: user-memory-access in fib6_drop_pcpu_from net/ipv6/ip6_fib.c:927 [inline]
  24 BUG: KASAN: user-memory-access in fib6_purge_rt+0x4f6/0x670 net/ipv6/ip6_fib.c:960
  25 Write of size 4 at addr 0000000000ffffb4 by task syz-executor.1/7649
  26
  27 CPU: 0 PID: 7649 Comm: syz-executor.1 Not tainted 5.1.0-rc6+ #183
  28 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  29 Call Trace:
  30  __dump_stack lib/dump_stack.c:77 [inline]
  31  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  32  kasan_report.cold+0x5/0x40 mm/kasan/report.c:321
  33  check_memory_region_inline mm/kasan/generic.c:185 [inline]
  34  check_memory_region+0x123/0x190 mm/kasan/generic.c:191
  35  kasan_check_write+0x14/0x20 mm/kasan/common.c:108
  36  atomic_dec_and_test include/asm-generic/atomic-instrumented.h:747 [inline]
  37  fib6_info_release include/net/ip6_fib.h:294 [inline]
  38  fib6_info_release include/net/ip6_fib.h:292 [inline]
  39  fib6_drop_pcpu_from net/ipv6/ip6_fib.c:927 [inline]
  40  fib6_purge_rt+0x4f6/0x670 net/ipv6/ip6_fib.c:960
  41  fib6_del_route net/ipv6/ip6_fib.c:1813 [inline]
  42  fib6_del+0xac2/0x10a0 net/ipv6/ip6_fib.c:1844
  43  fib6_clean_node+0x3a8/0x590 net/ipv6/ip6_fib.c:2006
  44  fib6_walk_continue+0x495/0x900 net/ipv6/ip6_fib.c:1928
  45  fib6_walk+0x9d/0x100 net/ipv6/ip6_fib.c:1976
  46  fib6_clean_tree+0xe0/0x120 net/ipv6/ip6_fib.c:2055
  47  __fib6_clean_all+0x118/0x2a0 net/ipv6/ip6_fib.c:2071
  48  fib6_clean_all+0x2b/0x40 net/ipv6/ip6_fib.c:2082
  49  rt6_sync_down_dev+0x134/0x150 net/ipv6/route.c:4057
  50  rt6_disable_ip+0x27/0x5f0 net/ipv6/route.c:4062
  51  addrconf_ifdown+0xa2/0x1220 net/ipv6/addrconf.c:3705
  52  addrconf_notify+0x19a/0x2260 net/ipv6/addrconf.c:3630
  53  notifier_call_chain+0xc7/0x240 kernel/notifier.c:93
  54  __raw_notifier_call_chain kernel/notifier.c:394 [inline]
  55  raw_notifier_call_chain+0x2e/0x40 kernel/notifier.c:401
  56  call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1753
  57  call_netdevice_notifiers_extack net/core/dev.c:1765 [inline]
  58  call_netdevice_notifiers net/core/dev.c:1779 [inline]
  59  dev_close_many+0x33f/0x6f0 net/core/dev.c:1522
  60  rollback_registered_many+0x43b/0xfd0 net/core/dev.c:8177
  61  rollback_registered+0x109/0x1d0 net/core/dev.c:8242
  62  unregister_netdevice_queue net/core/dev.c:9289 [inline]
  63  unregister_netdevice_queue+0x1ee/0x2c0 net/core/dev.c:9282
  64  unregister_netdevice include/linux/netdevice.h:2658 [inline]
  65  __tun_detach+0xd5b/0x1000 drivers/net/tun.c:727
  66  tun_detach drivers/net/tun.c:744 [inline]
  67  tun_chr_close+0xe0/0x180 drivers/net/tun.c:3443
  68  __fput+0x2e5/0x8d0 fs/file_table.c:278
  69  ____fput+0x16/0x20 fs/file_table.c:309
  70  task_work_run+0x14a/0x1c0 kernel/task_work.c:113
  71  exit_task_work include/linux/task_work.h:22 [inline]
  72  do_exit+0x90a/0x2fa0 kernel/exit.c:876
  73  do_group_exit+0x135/0x370 kernel/exit.c:980
  74  __do_sys_exit_group kernel/exit.c:991 [inline]
  75  __se_sys_exit_group kernel/exit.c:989 [inline]
  76  __x64_sys_exit_group+0x44/0x50 kernel/exit.c:989
  77  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
  78  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  79 RIP: 0033:0x458da9
  80 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
  81 RSP: 002b:00007ffeafc2a6a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
  82 RAX: ffffffffffffffda RBX: 000000000000001c RCX: 0000000000458da9
  83 RDX: 0000000000412a80 RSI: 0000000000a54ef0 RDI: 0000000000000043
  84 RBP: 00000000004be552 R08: 000000000000000c R09: 000000000004c0d1
  85 R10: 0000000002341940 R11: 0000000000000246 R12: 00000000ffffffff
  86 R13: 00007ffeafc2a7f0 R14: 000000000004c065 R15: 00007ffeafc2a800
  87
  88 Fixes: a68886a69180 ("net/ipv6: Make from in rt6_info rcu protected")
  89 Signed-off-by: Eric Dumazet <edumazet@google.com>
  90 Reported-by: syzbot <syzkaller@googlegroups.com>
  91 Cc: David Ahern <dsahern@gmail.com>
  92 Reviewed-by: David Ahern <dsahern@gmail.com>
  93 Acked-by: Martin KaFai Lau <kafai@fb.com>
  94 Acked-by: Wei Wang <weiwan@google.com>
  95 Signed-off-by: David S. Miller <davem@davemloft.net>
  96 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  97 ---
  98  net/ipv6/ip6_fib.c |    4 +---
  99  net/ipv6/route.c   |    9 ++-------
 100  2 files changed, 3 insertions(+), 10 deletions(-)
 101
 102 --- a/net/ipv6/ip6_fib.c
 103 +++ b/net/ipv6/ip6_fib.c
 104 @@ -889,9 +889,7 @@ static void fib6_drop_pcpu_from(struct f
 105                 if (pcpu_rt) {
 106                         struct fib6_info *from;
 107
 108 -                       from = rcu_dereference_protected(pcpu_rt->from,
 109 -                                            lockdep_is_held(&table->tb6_lock));
 110 -                       rcu_assign_pointer(pcpu_rt->from, NULL);
 111 +                       from = xchg((__force struct fib6_info **)&pcpu_rt->from, NULL);
 112                         fib6_info_release(from);
 113                 }
 114         }
 115 --- a/net/ipv6/route.c
 116 +++ b/net/ipv6/route.c
 117 @@ -382,11 +382,8 @@ static void ip6_dst_destroy(struct dst_e
 118                 in6_dev_put(idev);
 119         }
 120
 121 -       rcu_read_lock();
 122 -       from = rcu_dereference(rt->from);
 123 -       rcu_assign_pointer(rt->from, NULL);
 124 +       from = xchg((__force struct fib6_info **)&rt->from, NULL);
 125         fib6_info_release(from);
 126 -       rcu_read_unlock();
 127  }
 128
 129  static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 130 @@ -1296,9 +1293,7 @@ static void rt6_remove_exception(struct
 131         /* purge completely the exception to allow releasing the held resources:
 132          * some [sk] cache may keep the dst around for unlimited time
 133          */
 134 -       from = rcu_dereference_protected(rt6_ex->rt6i->from,
 135 -                                        lockdep_is_held(&rt6_exception_lock));
 136 -       rcu_assign_pointer(rt6_ex->rt6i->from, NULL);
 137 +       from = xchg((__force struct fib6_info **)&rt6_ex->rt6i->from, NULL);
 138         fib6_info_release(from);
 139         dst_dev_put(&rt6_ex->rt6i->dst);
 140