Date:   Mon, 02 Apr 2018 10:01:02 -0700
From:   syzbot <syzbot+aed06913f36eff9b544e@...kaller.appspotmail.com>
To:     anton@...era.com, linux-kernel@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net,
        syzkaller-bugs@...glegroups.com
Subject: KASAN: slab-out-of-bounds Read in ntfs_attr_find

Hello,

syzbot hit the following crash on upstream commit
0adb32858b0bddf4ada5f364a84ed60b196dbcda (Sun Apr 1 21:20:27 2018 +0000)
Linux 4.16
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5967192604540928
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5683233123467264
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=6754575268708352
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-2374466361298166459
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+aed06913f36eff9b544e@...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.

ntfs: (device loop0): is_boot_sector_ntfs(): Invalid end of sector marker.
==================================================================
BUG: KASAN: slab-out-of-bounds in ntfs_attr_find+0x99a/0xa00  
fs/ntfs/attrib.c:613
Read of size 4 at addr ffff8801d96bfbb5 by task syzkaller786329/4469

CPU: 0 PID: 4469 Comm: syzkaller786329 Not tainted 4.16.0+ #10
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_load_n_noabort+0xf/0x20 mm/kasan/report.c:443
  ntfs_attr_find+0x99a/0xa00 fs/ntfs/attrib.c:613
  ntfs_attr_lookup+0x10e1/0x22a0 fs/ntfs/attrib.c:1203
  ntfs_read_inode_mount+0x6cd/0x20f0 fs/ntfs/inode.c:1858
  ntfs_fill_super+0x13df/0x2fb0 fs/ntfs/super.c:2871
  mount_bdev+0x2b7/0x370 fs/super.c:1119
  ntfs_mount+0x34/0x40 fs/ntfs/super.c:3065
  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
RIP: 0033:0x442eca
RSP: 002b:00007ffce22e1a98 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000442eca
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffce22e1aa0
RBP: 00000000006cb018 R08: 000000002007e200 R09: 000000000000000a
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000004
R13: 0000000000401dc0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 2834:
  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
  __do_kmalloc_node mm/slab.c:3670 [inline]
  __kmalloc_node+0x47/0x70 mm/slab.c:3677
  kmalloc_node include/linux/slab.h:554 [inline]
  kvmalloc_node+0x99/0xd0 mm/util.c:419
  kvmalloc include/linux/mm.h:541 [inline]
  seq_buf_alloc fs/seq_file.c:29 [inline]
  seq_read+0x7fc/0x1410 fs/seq_file.c:208
  __vfs_read+0xef/0xa00 fs/read_write.c:411
  vfs_read+0x11e/0x350 fs/read_write.c:447
  SYSC_read fs/read_write.c:573 [inline]
  SyS_read+0xef/0x220 fs/read_write.c:566
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 2834:
  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
  kvfree+0x36/0x60 mm/util.c:438
  seq_release fs/seq_file.c:368 [inline]
  single_release+0x78/0xb0 fs/seq_file.c:605
  __fput+0x327/0x7e0 fs/file_table.c:209
  ____fput+0x15/0x20 fs/file_table.c:243
  task_work_run+0x199/0x270 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
  exit_to_usermode_loop+0x275/0x2f0 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

The buggy address belongs to the object at ffff8801d96be180
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 2613 bytes to the right of
  4096-byte region [ffff8801d96be180, ffff8801d96bf180)
The buggy address belongs to the page:
page:ffffea000765af80 count:1 mapcount:0 mapping:ffff8801d96be180 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d96be180 0000000000000000 0000000100000001
raw: ffffea0006b1b820 ffffea0007622ba0 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d96bfa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d96bfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d96bfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                      ^
  ffff8801d96bfc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d96bfc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
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