syzbot

loop0: detected capacity change from 0 to 32768
JBD2: Ignoring recovery information on journal
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
------------[ cut here ]------------
memset: detected buffer overflow: 384 byte write of buffer size 16
WARNING: lib/string_helpers.c:1037 at __fortify_report+0x6b/0xa0 lib/string_helpers.c:1036, CPU#0: syz.0.0/5313
Modules linked in:
CPU: 0 UID: 0 PID: 5313 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__fortify_report+0x89/0xa0 lib/string_helpers.c:1036
Code: e8 8c 76 7e fd 48 8d 3d a5 8f 87 0b 45 84 e4 49 8b 37 48 c7 c0 40 77 28 8c 48 c7 c1 60 77 28 8c 48 0f 44 c8 4c 89 f2 49 89 d8 <67> 48 0f b9 3a 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc cc cc cc cc
RSP: 0018:ffffc9000df06bc8 EFLAGS: 00010202
RAX: ffffffff8c287740 RBX: 0000000000000010 RCX: ffffffff8c287760
RDX: 0000000000000180 RSI: ffffffff8c287600 RDI: ffffffff903bfb70
RBP: 000000000000000f R08: 0000000000000010 R09: 1ffffffff20621de
R10: dffffc0000000000 R11: fffffbfff20621df R12: 0000000000000001
R13: 1ffff1100ac9db50 R14: 0000000000000180 R15: ffffffff8c287438
FS:  00007f5ae04fd6c0(0000) GS:ffff88808c886000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f562556a540 CR3: 0000000036d11000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __fortify_panic+0x9/0x10 lib/string_helpers.c:1043
 fortify_memset_chk include/linux/fortify-string.h:495 [inline]
 ocfs2_remove_refcount_extent fs/ocfs2/refcounttree.c:2134 [inline]
 ocfs2_decrease_refcount_rec fs/ocfs2/refcounttree.c:2203 [inline]
 __ocfs2_decrease_refcount+0x195b/0x19a0 fs/ocfs2/refcounttree.c:2249
 ocfs2_decrease_refcount+0x59c/0x7d0 fs/ocfs2/refcounttree.c:2312
 ocfs2_remove_btree_range+0x1223/0x15f0 fs/ocfs2/alloc.c:5800
 ocfs2_commit_truncate+0xc60/0x2560 fs/ocfs2/alloc.c:7383
 ocfs2_truncate_file+0xd24/0x1530 fs/ocfs2/file.c:510
 ocfs2_setattr+0x1641/0x1d10 fs/ocfs2/file.c:1219
 notify_change+0xbba/0xea0 fs/attr.c:556
 do_truncate+0x1c2/0x250 fs/open.c:68
 vfs_truncate+0x4b4/0x540 fs/open.c:118
 ksys_truncate+0xf3/0x1c0 fs/open.c:142
 __do_sys_truncate fs/open.c:154 [inline]
 __se_sys_truncate fs/open.c:152 [inline]
 __x64_sys_truncate+0x5b/0x70 fs/open.c:152
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5adf59ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5ae04fcfe8 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f5adf815fa0 RCX: 00007f5adf59ce59
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 00002000000000c0
RBP: 00007f5adf632d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5adf816038 R14: 00007f5adf815fa0 R15: 00007ffea3f76b98
 </TASK>
----------------
Code disassembly (best guess):
   0:	e8 8c 76 7e fd       	call   0xfd7e7691
   5:	48 8d 3d a5 8f 87 0b 	lea    0xb878fa5(%rip),%rdi        # 0xb878fb1
   c:	45 84 e4             	test   %r12b,%r12b
   f:	49 8b 37             	mov    (%r15),%rsi
  12:	48 c7 c0 40 77 28 8c 	mov    $0xffffffff8c287740,%rax
  19:	48 c7 c1 60 77 28 8c 	mov    $0xffffffff8c287760,%rcx
  20:	48 0f 44 c8          	cmove  %rax,%rcx
  24:	4c 89 f2             	mov    %r14,%rdx
  27:	49 89 d8             	mov    %rbx,%r8
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	5b                   	pop    %rbx
  30:	41 5c                	pop    %r12
  32:	41 5e                	pop    %r14
  34:	41 5f                	pop    %r15
  36:	5d                   	pop    %rbp
  37:	c3                   	ret
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	cc                   	int3
  3c:	cc                   	int3
  3d:	cc                   	int3
  3e:	cc                   	int3
  3f:	cc                   	int3