Date:   Sat, 31 Mar 2018 13:47:05 -0700
From:   syzbot <syzbot+040b31ac96753fd7eb46@...kaller.appspotmail.com>
To:     bfoster@...hat.com, billodo@...hat.com, cmaiolino@...hat.com,
        colin.king@...onical.com, darrick.wong@...cle.com,
        dchinner@...hat.com, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: KASAN: use-after-free Read in radix_tree_next_chunk

Hello,

syzbot hit the following crash on upstream commit
9dd2326890d89a5179967c947dab2bab34d7ddee (Fri Mar 30 17:29:47 2018 +0000)
Merge tag 'ceph-for-4.16-rc8' of git://github.com/ceph/ceph-client
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=040b31ac96753fd7eb46

So far this crash happened 50 times on upstream.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6534913729757184
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=6221692233842688
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=5252920484298752
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-2760467897697295172
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+040b31ac96753fd7eb46@...kaller.appspotmail.com
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.

IPVS: ftp: loaded support on port[0] = 21
XFS (loop5): Invalid device [./file0], error=-15
XFS (loop7): nobarrier option is deprecated, ignoring.
XFS (loop7): Invalid device [./file0], error=-15
==================================================================
BUG: KASAN: use-after-free in radix_tree_next_chunk+0xde1/0xdf0  
lib/radix-tree.c:1733
Read of size 4 at addr ffff8801b1669250 by task syzkaller476032/4458

CPU: 1 PID: 4458 Comm: syzkaller476032 Not tainted 4.16.0-rc7+ #7
IPVS: ftp: loaded support on port[0] = 21
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+0x194/0x24d lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23c/0x360 mm/kasan/report.c:412
  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
  radix_tree_next_chunk+0xde1/0xdf0 lib/radix-tree.c:1733
  radix_tree_gang_lookup_tag+0x36e/0x5e0 lib/radix-tree.c:1918
IPVS: ftp: loaded support on port[0] = 21
  xfs_perag_get_tag+0x109/0x6c0 fs/xfs/libxfs/xfs_sb.c:88
IPVS: ftp: loaded support on port[0] = 21
  xfs_reclaim_inodes_count+0x82/0xb0 fs/xfs/xfs_icache.c:1362
  xfs_fs_nr_cached_objects+0x37/0x50 fs/xfs/xfs_super.c:1778
  super_cache_count+0x96/0x280 fs/super.c:131
  do_shrink_slab mm/vmscan.c:310 [inline]
  shrink_slab.part.46+0x30c/0xe80 mm/vmscan.c:475
  shrink_slab+0x9d/0xb0 mm/vmscan.c:442
  shrink_node+0x51e/0xf70 mm/vmscan.c:2556
  shrink_zones mm/vmscan.c:2728 [inline]
  do_try_to_free_pages+0x383/0x1020 mm/vmscan.c:2790
  try_to_free_mem_cgroup_pages+0x44d/0xb40 mm/vmscan.c:3079
IPVS: ftp: loaded support on port[0] = 21
  reclaim_high.constprop.64+0x1e2/0x330 mm/memcontrol.c:1862
IPVS: ftp: loaded support on port[0] = 21
  mem_cgroup_handle_over_high+0x8d/0x130 mm/memcontrol.c:1887
  tracehook_notify_resume include/linux/tracehook.h:193 [inline]
  exit_to_usermode_loop+0x242/0x2f0 arch/x86/entry/common.c:166
  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
  do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x440fda
RSP: 002b:00007ffd309f1880 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: 0000000000000003 RBX: 0000000000000000 RCX: 0000000000440fda
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffd309f18a0 R08: 0000000000000001 R09: 00000000020eb880
R10: 00000000020ebb50 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd309f18d0 R14: 0000000000000000 R15: 00007ffd309f19e8

Allocated by task 4469:
  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:552
  kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3608
  kmalloc include/linux/slab.h:512 [inline]
  kzalloc include/linux/slab.h:701 [inline]
  xfs_fs_fill_super+0xd1/0x1220 fs/xfs/xfs_super.c:1579
  mount_bdev+0x2b7/0x370 fs/super.c:1119
  xfs_fs_mount+0x34/0x40 fs/xfs/xfs_super.c:1770
  mount_fs+0x66/0x2d0 fs/super.c:1222
  vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037
  vfs_kern_mount fs/namespace.c:2509 [inline]
  do_new_mount fs/namespace.c:2512 [inline]
  do_mount+0xea4/0x2bb0 fs/namespace.c:2842
  SYSC_mount fs/namespace.c:3058 [inline]
  SyS_mount+0xab/0x120 fs/namespace.c:3035
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4469:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
  __cache_free mm/slab.c:3486 [inline]
  kfree+0xd9/0x260 mm/slab.c:3801
  xfs_fs_fill_super+0x6c3/0x1220 fs/xfs/xfs_super.c:1734
  mount_bdev+0x2b7/0x370 fs/super.c:1119
  xfs_fs_mount+0x34/0x40 fs/xfs/xfs_super.c:1770
  mount_fs+0x66/0x2d0 fs/super.c:1222
  vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037
  vfs_kern_mount fs/namespace.c:2509 [inline]
  do_new_mount fs/namespace.c:2512 [inline]
  do_mount+0xea4/0x2bb0 fs/namespace.c:2842
  SYSC_mount fs/namespace.c:3058 [inline]
  SyS_mount+0xab/0x120 fs/namespace.c:3035
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801b1668e80
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 976 bytes inside of
  4096-byte region [ffff8801b1668e80, ffff8801b1669e80)
The buggy address belongs to the page:
page:ffffea0006c59a00 count:1 mapcount:0 mapping:ffff8801b1668e80 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801b1668e80 0000000000000000 0000000100000001
raw: ffffea0006c5a2a0 ffffea0006cc47a0 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801b1669100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801b1669180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801b1669200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                  ^
  ffff8801b1669280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801b1669300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
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