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

[Cong Wang]

On Tue, Jan 9, 2018 at 2:58 PM, syzbot
<syzbot+e3eeae78ea88b8d6d858@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> 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: syzbot+e3eeae78ea88b8d6d858@xxxxxxxxxxxxxxxxxxxxxxxxx
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> 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

Blame this:

commit d12d2e12cec2d66eab6cd58f592dad9fd386b97d
Author: Jon Maloy <jon.maloy@xxxxxxxxxxxx>
Date:   Mon Jan 8 21:03:28 2018 +0100

    tipc: send out join messages as soon as new member is discovered


which assumes a return when tipc_sk_publish() fails but we don't.


> 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
> ==================================================================
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
>
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
> #syz fix: exact-commit-title
> If you want to test a patch for this bug, please reply with:
> #syz test: git://repo/address.git branch
> and provide the patch inline or as an attachment.
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line in the email body.