Date:   Tue, 06 Mar 2018 22:59:03 -0800
From:   syzbot <syzbot+dcfd344365a56fbebd0f@...kaller.appspotmail.com>
To:     dasaratharaman.chandramouli@...el.com, dledford@...hat.com,
        don.hiatt@...el.com, jgg@...pe.ca, leon@...nel.org,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        parav@...lanox.com, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk
Subject: KASAN: use-after-free Read in ucma_close

Hello,

syzbot hit the following crash on upstream commit
ce380619fab99036f5e745c7a865b21c59f005f6 (Tue Mar 6 04:31:14 2018 +0000)
Merge tag 'please-pull-ia64_misc' of  
git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux

So far this crash happened 6 times on upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+dcfd344365a56fbebd0f@...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.

audit: type=1400 audit(1520366586.501:7): avc:  denied  { map } for   
pid=4239 comm="syzkaller296139" path="/root/syzkaller296139392" 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
==================================================================
audit: type=1400 audit(1520366586.511:8): avc:  denied  { map } for   
pid=4239 comm="syzkaller296139" path=2F6D656D66643A49202864656C6574656429  
dev="tmpfs" ino=13679  
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:tmpfs_t:s0 tclass=file permissive=1
BUG: KASAN: use-after-free in ucma_close+0x2d7/0x2f0  
drivers/infiniband/core/ucma.c:1687
Read of size 8 at addr ffff8801af1739c0 by task syzkaller296139/4243

CPU: 1 PID: 4243 Comm: syzkaller296139 Not tainted 4.16.0-rc4+ #343
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_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  ucma_close+0x2d7/0x2f0 drivers/infiniband/core/ucma.c:1687
  __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
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73a/0x16d0 kernel/signal.c:2469
  do_signal+0x90/0x1e90 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:162
  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: 0033:0x445619
RSP: 002b:00007f603ee58da8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: 0000000000000001 RBX: 00000000006dac3c RCX: 0000000000445619
RDX: 0000000000445619 RSI: 0000000000000001 RDI: 00000000006dac3c
RBP: 00000000006dac38 R08: 0000000000000000 R09: 0000000000000000
R10: 00007f603ee59700 R11: 0000000000000246 R12: 006d635f616d6472
R13: 2f646e6162696e69 R14: 666e692f7665642f R15: 0000000000000004

Allocated by task 4240:
  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:3607
  kmalloc include/linux/slab.h:512 [inline]
  kzalloc include/linux/slab.h:701 [inline]
  ucma_alloc_ctx+0xce/0x610 drivers/infiniband/core/ucma.c:188
  ucma_create_id+0x205/0x620 drivers/infiniband/core/ucma.c:473
  ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1627
  __vfs_write+0xef/0x970 fs/read_write.c:480
  vfs_write+0x189/0x510 fs/read_write.c:544
  SYSC_write fs/read_write.c:589 [inline]
  SyS_write+0xef/0x220 fs/read_write.c:581
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4240:
  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:3485 [inline]
  kfree+0xd9/0x260 mm/slab.c:3800
  ucma_create_id+0x45b/0x620 drivers/infiniband/core/ucma.c:500
  ucma_write+0x2d6/0x3d0 drivers/infiniband/core/ucma.c:1627
  __vfs_write+0xef/0x970 fs/read_write.c:480
  vfs_write+0x189/0x510 fs/read_write.c:544
  SYSC_write fs/read_write.c:589 [inline]
  SyS_write+0xef/0x220 fs/read_write.c:581
  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 ffff8801af173940
  which belongs to the cache kmalloc-256 of size 256
The buggy address is located 128 bytes inside of
  256-byte region [ffff8801af173940, ffff8801af173a40)
The buggy address belongs to the page:
page:ffffea0006bc5cc0 count:1 mapcount:0 mapping:ffff8801af173080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801af173080 0000000000000000 000000010000000c
raw: ffffea0006bda620 ffff8801dac01648 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801af173880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801af173900: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff8801af173980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                            ^
  ffff8801af173a00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
  ffff8801af173a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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