Subject: KASAN: use-after-free Read in rb_first_postorder

From: syzbot <[email-masked]>
Date: Tue, 09 Jan 2018 14:58:01 -0800

Hello,

syzkaller hit the following crash on  
61ad64080e039dce99a7f8d89b729bbea995e2f7
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
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details.
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audit: type=1400 audit(1515534326.722:7): avc:  denied  { map } for   
pid=3495 comm="syzkaller785641" path="/root/syzkaller785641882" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in rb_first_postorder+0x7c/0xa0 lib/rbtree.c:671
Read of size 8 at addr ffff8801d9929c00 by task syzkaller785641/3495

CPU: 0 PID: 3495 Comm: syzkaller785641 Not tainted 4.15.0-rc7+ #181
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:252
  kasan_report_error mm/kasan/report.c:351 [inline]
  kasan_report+0x25b/0x340 mm/kasan/report.c:409
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
  rb_first_postorder+0x7c/0xa0 lib/rbtree.c:671
  tipc_group_join+0x120/0x2d0 net/tipc/group.c:210
  tipc_sk_join net/tipc/socket.c:2781 [inline]
  tipc_setsockopt+0x67e/0xcc0 net/tipc/socket.c:2876
  SYSC_setsockopt net/socket.c:1821 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1800
  entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x43fca9
RSP: 002b:00007ffe286872e8 EFLAGS: 00000203 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fca9
RDX: 0000000000000087 RSI: 000000000000010f RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000010 R09: 0000000000000000
R10: 0000000020540ff0 R11: 0000000000000203 R12: 0000000000401610
R13: 00000000004016a0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3495:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
  kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
  kmalloc include/linux/slab.h:499 [inline]
  kzalloc include/linux/slab.h:688 [inline]
  tipc_group_create+0x144/0x900 net/tipc/group.c:180
  tipc_sk_join net/tipc/socket.c:2762 [inline]
  tipc_setsockopt+0x274/0xcc0 net/tipc/socket.c:2876
  SYSC_setsockopt net/socket.c:1821 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1800
  entry_SYSCALL_64_fastpath+0x23/0x9a

Freed by task 3495:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
  __cache_free mm/slab.c:3488 [inline]
  kfree+0xd6/0x260 mm/slab.c:3803
  tipc_group_delete+0x2c8/0x3d0 net/tipc/group.c:234
  tipc_sk_join net/tipc/socket.c:2775 [inline]
  tipc_setsockopt+0xba3/0xcc0 net/tipc/socket.c:2876
  SYSC_setsockopt net/socket.c:1821 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1800
  entry_SYSCALL_64_fastpath+0x23/0x9a

The buggy address belongs to the object at ffff8801d9929c00
  which belongs to the cache kmalloc-128 of size 128
The buggy address is located 0 bytes inside of
  128-byte region [ffff8801d9929c00, ffff8801d9929c80)
The buggy address belongs to the page:
page:ffffea0007664a40 count:1 mapcount:0 mapping:ffff8801d9929000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d9929000 0000000000000000 0000000100000015
raw: ffffea0007660ca0 ffffea0007665020 ffff8801dac00640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d9929b00: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
  ffff8801d9929b80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ffff8801d9929c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff8801d9929c80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
  ffff8801d9929d00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
==================================================================

---
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