Subject: KASAN: slab-out-of-bounds Read in ip6_tnl_parse_tlv_enc_lim

From: syzbot <[email-masked]>
Date: Mon, 17 Sep 2018 14:23:03 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    3a5af36b6d0e Merge tag '4.19-rc3-smb3-cifs' of git://git.s..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15c727be400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9c4a80625153107e
dashboard link: https://syzkaller.appspot.com/bug?extid=68dce7caebd8543121de
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1068a44e400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=146386c6400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
==================================================================
BUG: KASAN: slab-out-of-bounds in ip6_tnl_parse_tlv_enc_lim+0x5df/0x660  
net/ipv6/ip6_tunnel.c:417
Read of size 1 at addr ffff8801d21187c7 by task syz-executor281/5345

CPU: 1 PID: 5345 Comm: syz-executor281 Not tainted 4.19.0-rc3+ #238
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+0x1c4/0x2b4 lib/dump_stack.c:113
  print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
  ip6_tnl_parse_tlv_enc_lim+0x5df/0x660 net/ipv6/ip6_tunnel.c:417
  ip6ip6_tnl_xmit net/ipv6/ip6_tunnel.c:1339 [inline]
  ip6_tnl_start_xmit+0x3e2/0x2370 net/ipv6/ip6_tunnel.c:1403
  __netdev_start_xmit include/linux/netdevice.h:4287 [inline]
  netdev_start_xmit include/linux/netdevice.h:4296 [inline]
  xmit_one net/core/dev.c:3216 [inline]
  dev_hard_start_xmit+0x27f/0xc70 net/core/dev.c:3232
  __dev_queue_xmit+0x2f3b/0x3980 net/core/dev.c:3802
  dev_queue_xmit+0x17/0x20 net/core/dev.c:3835
  __bpf_tx_skb net/core/filter.c:2012 [inline]
  __bpf_redirect_common net/core/filter.c:2050 [inline]
  __bpf_redirect+0x5cf/0xb20 net/core/filter.c:2057
  ____bpf_clone_redirect net/core/filter.c:2090 [inline]
  bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062
  bpf_prog_759a992c578a3894+0x741/0x1000

Allocated by task 5345:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
  __do_kmalloc_node mm/slab.c:3682 [inline]
  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696
  __kmalloc_reserve.isra.39+0x41/0xe0 net/core/skbuff.c:137
  pskb_expand_head+0x230/0x10f0 net/core/skbuff.c:1460
  skb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5126
  __bpf_try_make_writable net/core/filter.c:1633 [inline]
  bpf_try_make_writable net/core/filter.c:1639 [inline]
  bpf_try_make_head_writable net/core/filter.c:1647 [inline]
  ____bpf_clone_redirect net/core/filter.c:2084 [inline]
  bpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062
  bpf_prog_759a992c578a3894+0x741/0x1000

Freed by task 3895:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xcf/0x230 mm/slab.c:3813
  load_elf_binary+0x25b4/0x5620 fs/binfmt_elf.c:1118
  search_binary_handler+0x17d/0x570 fs/exec.c:1653
  exec_binprm fs/exec.c:1695 [inline]
  __do_execve_file.isra.33+0x162f/0x2540 fs/exec.c:1819
  do_execveat_common fs/exec.c:1866 [inline]
  do_execve fs/exec.c:1883 [inline]
  __do_sys_execve fs/exec.c:1964 [inline]
  __se_sys_execve fs/exec.c:1959 [inline]
  __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959
  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 ffff8801d21185c0
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 7 bytes to the right of
  512-byte region [ffff8801d21185c0, ffff8801d21187c0)
The buggy address belongs to the page:
page:ffffea0007484600 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007484008 ffffea0007487e88 ffff8801da800940
raw: 0000000000000000 ffff8801d21180c0 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d2118680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801d2118700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801d2118780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
                                            ^
  ffff8801d2118800: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
  ffff8801d2118880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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