Date:   Tue, 03 Apr 2018 10:01:01 -0700
From:   syzbot <syzbot+08ab33be0178b76851c8@...kaller.appspotmail.com>
To:     bfoster@...hat.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 xfs_inobt_init_key_from_rec

Hello,

syzbot hit the following crash on upstream commit
642e7fd23353e22290e3d51719fcb658dc252342 (Tue Apr 3 04:22:12 2018 +0000)
Merge branch 'syscalls-next' of  
git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=08ab33be0178b76851c8

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5951352765153280
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5417464171069440
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=6712144213049344
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-6874493495260513980
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+08ab33be0178b76851c8@...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.

XFS (loop0): Mounting V4 Filesystem
XFS (loop0): totally zeroed log
==================================================================
BUG: KASAN: use-after-free in xfs_inobt_init_key_from_rec+0x6a/0x70  
fs/xfs/libxfs/xfs_ialloc_btree.c:195
Read of size 4 at addr ffff8801af98cf00 by task syzkaller185183/4464

CPU: 0 PID: 4464 Comm: syzkaller185183 Not tainted 4.16.0+ #12
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+0x1a7/0x27d 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
  xfs_inobt_init_key_from_rec+0x6a/0x70 fs/xfs/libxfs/xfs_ialloc_btree.c:195
  xfs_lookup_get_search_key+0x7e/0xc0 fs/xfs/libxfs/xfs_btree.c:1858
  xfs_btree_lookup+0x932/0x1180 fs/xfs/libxfs/xfs_btree.c:1948
  xfs_inobt_lookup fs/xfs/libxfs/xfs_ialloc.c:75 [inline]
  xfs_imap_lookup+0x216/0x640 fs/xfs/libxfs/xfs_ialloc.c:2235
  xfs_imap+0x78f/0x960 fs/xfs/libxfs/xfs_ialloc.c:2364
  xfs_iread+0xc7/0x770 fs/xfs/libxfs/xfs_inode_buf.c:556
  xfs_iget_cache_miss fs/xfs/xfs_icache.c:475 [inline]
  xfs_iget+0xcec/0x3060 fs/xfs/xfs_icache.c:626
  xfs_mountfs+0x139a/0x2690 fs/xfs/xfs_mount.c:881
  xfs_fs_fill_super+0xc8d/0x1250 fs/xfs/xfs_super.c:1703
  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:2514 [inline]
  do_new_mount fs/namespace.c:2517 [inline]
  do_mount+0xea4/0x2b90 fs/namespace.c:2847
  ksys_mount+0xab/0x120 fs/namespace.c:3063
  SYSC_mount fs/namespace.c:3077 [inline]
  SyS_mount+0x39/0x50 fs/namespace.c:3074
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x44371a
RSP: 002b:00007fff43e464c8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000840 RCX: 000000000044371a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fff43e464d0
RBP: 0000000000000003 R08: 0000000020018900 R09: 000000000000000a
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000004
R13: 0000000000402610 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 4462:
  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
  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3542
  getname_flags+0xcb/0x580 fs/namei.c:138
  getname+0x19/0x20 fs/namei.c:209
  do_sys_open+0x2e7/0x6d0 fs/open.c:1095
  SYSC_open fs/open.c:1119 [inline]
  SyS_open+0x2d/0x40 fs/open.c:1114
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4462:
  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]
  kmem_cache_free+0x83/0x2a0 mm/slab.c:3744
  putname+0xee/0x130 fs/namei.c:258
  do_sys_open+0x31b/0x6d0 fs/open.c:1110
  SYSC_open fs/open.c:1119 [inline]
  SyS_open+0x2d/0x40 fs/open.c:1114
  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 ffff8801af98c600
  which belongs to the cache names_cache of size 4096
The buggy address is located 2304 bytes inside of
  4096-byte region [ffff8801af98c600, ffff8801af98d600)
The buggy address belongs to the page:
page:ffffea0006be6300 count:1 mapcount:0 mapping:ffff8801af98c600 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801af98c600 0000000000000000 0000000100000001
raw: ffffea0006be7aa0 ffffea0006be5f20 ffff8801da5ea600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801af98ce00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801af98ce80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801af98cf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff8801af98cf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801af98d000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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