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[67.180.167.114]) by smtp.gmail.com with ESMTPSA id a77-v6sm26150504pfj.38.2018.07.31.04.50.41 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 31 Jul 2018 04:50:41 -0700 (PDT) Subject: Re: KASAN: use-after-free Read in refcount_sub_and_test To: syzbot , davem@davemloft.net, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, Sabrina Dubroca References: <000000000000c5132b0572474587@google.com> From: Eric Dumazet Message-ID: <35e26006-8334-a4c7-840c-66be89354b81@gmail.com> Date: Tue, 31 Jul 2018 04:50:40 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <000000000000c5132b0572474587@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/31/2018 01:22 AM, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit:    61f4b23769f0 netlink: Don't shift with UB on nlk->ngroups > git tree:       net > console output: https://syzkaller.appspot.com/x/log.txt?x=16ed5cf0400000 > kernel config:  https://syzkaller.appspot.com/x/.config?x=ffb4428fdc82f93b > dashboard link: https://syzkaller.appspot.com/bug?extid=8c17db54fd0c0a2ee849 > compiler:       gcc (GCC) 8.0.1 20180413 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+8c17db54fd0c0a2ee849@syzkaller.appspotmail.com > > device lo left promiscuous mode > ================================================================== > BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline] > BUG: KASAN: use-after-free in refcount_sub_and_test+0x9a/0x350 lib/refcount.c:179 > Read of size 4 at addr ffff8801d96d2844 by task syz-executor1/4479 > > CPU: 0 PID: 4479 Comm: syz-executor1 Not tainted 4.18.0-rc6+ #34 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: >  __dump_stack lib/dump_stack.c:77 [inline] >  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 >  print_address_description+0x6c/0x20b mm/kasan/report.c:256 >  kasan_report_error mm/kasan/report.c:354 [inline] >  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412 >  check_memory_region_inline mm/kasan/kasan.c:260 [inline] >  check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267 >  kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272 >  atomic_read include/asm-generic/atomic-instrumented.h:21 [inline] >  refcount_sub_and_test+0x9a/0x350 lib/refcount.c:179 >  refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212 >  fib6_metrics_release+0x4f/0x90 net/ipv6/ip6_fib.c:178 >  fib6_drop_pcpu_from net/ipv6/ip6_fib.c:899 [inline] >  fib6_purge_rt+0x5ec/0x7f0 net/ipv6/ip6_fib.c:934 >  fib6_del_route net/ipv6/ip6_fib.c:1784 [inline] >  fib6_del+0xc11/0x1310 net/ipv6/ip6_fib.c:1815 >  fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976 >  fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899 >  fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947 >  fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024 >  __fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040 >  fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:2051 >  rt6_sync_down_dev net/ipv6/route.c:4083 [inline] >  rt6_disable_ip+0x111/0x7e0 net/ipv6/route.c:4088 >  addrconf_ifdown+0x16f/0x1670 net/ipv6/addrconf.c:3650 >  addrconf_notify+0x6e9/0x27f0 net/ipv6/addrconf.c:3575 >  notifier_call_chain+0x180/0x390 kernel/notifier.c:93 >  __raw_notifier_call_chain kernel/notifier.c:394 [inline] >  raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401 >  call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1735 >  call_netdevice_notifiers net/core/dev.c:1753 [inline] >  dev_close_many+0x447/0x8d0 net/core/dev.c:1505 >  rollback_registered_many+0x52b/0xef0 net/core/dev.c:7452 >  rollback_registered+0x1e9/0x420 net/core/dev.c:7517 >  unregister_netdevice_queue+0x32f/0x660 net/core/dev.c:8561 >  unregister_netdevice include/linux/netdevice.h:2548 [inline] >  __tun_detach+0x11d1/0x15e0 drivers/net/tun.c:727 >  tun_detach drivers/net/tun.c:744 [inline] >  tun_chr_close+0xe3/0x180 drivers/net/tun.c:3271 >  __fput+0x355/0x8b0 fs/file_table.c:209 >  ____fput+0x15/0x20 fs/file_table.c:243 >  task_work_run+0x1ec/0x2a0 kernel/task_work.c:113 >  exit_task_work include/linux/task_work.h:22 [inline] >  do_exit+0x1b08/0x2750 kernel/exit.c:865 >  do_group_exit+0x177/0x440 kernel/exit.c:968 >  __do_sys_exit_group kernel/exit.c:979 [inline] >  __se_sys_exit_group kernel/exit.c:977 [inline] >  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977 >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x456a09 > Code: Bad RIP value. > RSP: 002b:00007fffa8ff4908 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 > RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000456a09 > RDX: 00000000004104e0 RSI: 0000000000a44bd0 RDI: 0000000000000045 > RBP: 00000000004c1904 R08: 000000000000000b R09: 0000000000000000 > R10: 0000000001445940 R11: 0000000000000246 R12: 0000000001446940 > R13: 0000000000000000 R14: 000000000000057e R15: badc0ffeebadface > > Allocated by task 28651: >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >  set_track mm/kasan/kasan.c:460 [inline] >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 >  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620 >  kmalloc include/linux/slab.h:513 [inline] >  kzalloc include/linux/slab.h:707 [inline] >  fib6_metric_set+0x163/0x2c0 net/ipv6/ip6_fib.c:645 >  fib6_add_rt2node+0xe36/0x27f0 net/ipv6/ip6_fib.c:1000 >  fib6_add+0xaae/0x14d0 net/ipv6/ip6_fib.c:1308 >  __ip6_ins_rt+0x54/0x80 net/ipv6/route.c:1163 >  ip6_route_add+0x6d/0xc0 net/ipv6/route.c:3171 >  addrconf_prefix_route.isra.48+0x51d/0x720 net/ipv6/addrconf.c:2347 >  inet6_addr_modify net/ipv6/addrconf.c:4627 [inline] >  inet6_rtm_newaddr+0x112e/0x1b50 net/ipv6/addrconf.c:4743 >  rtnetlink_rcv_msg+0x46e/0xc30 net/core/rtnetlink.c:4665 >  netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2453 >  rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4683 >  netlink_unicast_kernel net/netlink/af_netlink.c:1315 [inline] >  netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1341 >  netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1906 >  sock_sendmsg_nosec net/socket.c:642 [inline] >  sock_sendmsg+0xd5/0x120 net/socket.c:652 >  ___sys_sendmsg+0x7fd/0x930 net/socket.c:2126 >  __sys_sendmsg+0x11d/0x290 net/socket.c:2164 >  __do_sys_sendmsg net/socket.c:2173 [inline] >  __se_sys_sendmsg net/socket.c:2171 [inline] >  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2171 >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Freed by task 4479: >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >  set_track mm/kasan/kasan.c:460 [inline] >  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 >  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 >  __cache_free mm/slab.c:3498 [inline] >  kfree+0xd9/0x260 mm/slab.c:3813 >  fib6_metrics_release+0x77/0x90 net/ipv6/ip6_fib.c:179 >  fib6_drop_pcpu_from net/ipv6/ip6_fib.c:899 [inline] >  fib6_purge_rt+0x5ec/0x7f0 net/ipv6/ip6_fib.c:934 >  fib6_del_route net/ipv6/ip6_fib.c:1784 [inline] >  fib6_del+0xc11/0x1310 net/ipv6/ip6_fib.c:1815 >  fib6_clean_node+0x3ee/0x5e0 net/ipv6/ip6_fib.c:1976 >  fib6_walk_continue+0x4b1/0x8e0 net/ipv6/ip6_fib.c:1899 >  fib6_walk+0x95/0xf0 net/ipv6/ip6_fib.c:1947 >  fib6_clean_tree+0x1ea/0x360 net/ipv6/ip6_fib.c:2024 >  __fib6_clean_all+0x21c/0x420 net/ipv6/ip6_fib.c:2040 >  fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:2051 >  rt6_sync_down_dev net/ipv6/route.c:4083 [inline] >  rt6_disable_ip+0x111/0x7e0 net/ipv6/route.c:4088 >  addrconf_ifdown+0x16f/0x1670 net/ipv6/addrconf.c:3650 >  addrconf_notify+0x6e9/0x27f0 net/ipv6/addrconf.c:3575 >  notifier_call_chain+0x180/0x390 kernel/notifier.c:93 >  __raw_notifier_call_chain kernel/notifier.c:394 [inline] >  raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401 >  call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1735 >  call_netdevice_notifiers net/core/dev.c:1753 [inline] >  dev_close_many+0x447/0x8d0 net/core/dev.c:1505 >  rollback_registered_many+0x52b/0xef0 net/core/dev.c:7452 >  rollback_registered+0x1e9/0x420 net/core/dev.c:7517 >  unregister_netdevice_queue+0x32f/0x660 net/core/dev.c:8561 >  unregister_netdevice include/linux/netdevice.h:2548 [inline] >  __tun_detach+0x11d1/0x15e0 drivers/net/tun.c:727 >  tun_detach drivers/net/tun.c:744 [inline] >  tun_chr_close+0xe3/0x180 drivers/net/tun.c:3271 >  __fput+0x355/0x8b0 fs/file_table.c:209 >  ____fput+0x15/0x20 fs/file_table.c:243 >  task_work_run+0x1ec/0x2a0 kernel/task_work.c:113 >  exit_task_work include/linux/task_work.h:22 [inline] >  do_exit+0x1b08/0x2750 kernel/exit.c:865 >  do_group_exit+0x177/0x440 kernel/exit.c:968 >  __do_sys_exit_group kernel/exit.c:979 [inline] >  __se_sys_exit_group kernel/exit.c:977 [inline] >  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977 >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > > The buggy address belongs to the object at ffff8801d96d2800 >  which belongs to the cache kmalloc-96 of size 96 > The buggy address is located 68 bytes inside of >  96-byte region [ffff8801d96d2800, ffff8801d96d2860) > The buggy address belongs to the page: > page:ffffea000765b480 count:1 mapcount:0 mapping:ffff8801dac004c0 index:0xffff8801d96d2700 > flags: 0x2fffc0000000100(slab) > raw: 02fffc0000000100 ffffea0006c46348 ffffea0006d0d288 ffff8801dac004c0 > raw: ffff8801d96d2700 ffff8801d96d2000 0000000100000003 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: >  ffff8801d96d2700: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >  ffff8801d96d2780: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >> ffff8801d96d2800: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >                                            ^ >  ffff8801d96d2880: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc >  ffff8801d96d2900: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ================================================================== > > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot. This might be caused by commit df18b50448fab1dff093731dfd0e25e77e1afcd1 Author: Sabrina Dubroca Date: Mon Jul 30 16:23:10 2018 +0200 net/ipv6: fix metrics leak