* rqst[1,2,3] is allocated in vars
* each rqst->rq_iov is also allocated in vars or using pooled memory

SMB2_open_free, SMB2_ioctl_free, SMB2_query_info_free are iterating on
each rqst after vars has been freed (use-after-free), and they are
freeing the kvec a second time (double-free).

How to trigger:

* compile with KASAN
* mount a share

$ smbinfo quota /mnt/foo
Segmentation fault
$ dmesg

 ==================================================================
 BUG: KASAN: use-after-free in SMB2_open_free+0x1c/0xa0
 Read of size 8 at addr ffff888007b10c00 by task python3/1200

 CPU: 2 PID: 1200 Comm: python3 Not tainted 5.12.0-rc6+ #107
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014
 Call Trace:
  dump_stack+0x93/0xc2
  print_address_description.constprop.0+0x18/0x130
  ? SMB2_open_free+0x1c/0xa0
  ? SMB2_open_free+0x1c/0xa0
  kasan_report.cold+0x7f/0x111
  ? smb2_ioctl_query_info+0x240/0x990
  ? SMB2_open_free+0x1c/0xa0
  SMB2_open_free+0x1c/0xa0
  smb2_ioctl_query_info+0x2bf/0x990
  ? smb2_query_reparse_tag+0x600/0x600
  ? cifs_mapchar+0x250/0x250
  ? rcu_read_lock_sched_held+0x3f/0x70
  ? cifs_strndup_to_utf16+0x12c/0x1c0
  ? rwlock_bug.part.0+0x60/0x60
  ? rcu_read_lock_sched_held+0x3f/0x70
  ? cifs_convert_path_to_utf16+0xf8/0x140
  ? smb2_check_message+0x6f0/0x6f0
  cifs_ioctl+0xf18/0x16b0
  ? smb2_query_reparse_tag+0x600/0x600
  ? cifs_readdir+0x1800/0x1800
  ? selinux_bprm_creds_for_exec+0x4d0/0x4d0
  ? do_user_addr_fault+0x30b/0x950
  ? __x64_sys_openat+0xce/0x140
  __x64_sys_ioctl+0xb9/0xf0
  do_syscall_64+0x33/0x40
  entry_SYSCALL_64_after_hwframe+0x44/0xae
 RIP: 0033:0x7fdcf1f4ba87
 Code: b3 66 90 48 8b 05 11 14 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e1 13 2c 00 f7 d8 64 89 01 48
 RSP: 002b:00007ffef1ce7748 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
 RAX: ffffffffffffffda RBX: 00000000c018cf07 RCX: 00007fdcf1f4ba87
 RDX: 0000564c467c5590 RSI: 00000000c018cf07 RDI: 0000000000000003
 RBP: 00007ffef1ce7770 R08: 00007ffef1ce7420 R09: 00007fdcf0e0562b
 R10: 0000000000000100 R11: 0000000000000246 R12: 0000000000004018
 R13: 0000000000000001 R14: 0000000000000003 R15: 0000564c467c5590

 Allocated by task 1200:
  kasan_save_stack+0x1b/0x40
  __kasan_kmalloc+0x7a/0x90
  smb2_ioctl_query_info+0x10e/0x990
  cifs_ioctl+0xf18/0x16b0
  __x64_sys_ioctl+0xb9/0xf0
  do_syscall_64+0x33/0x40
  entry_SYSCALL_64_after_hwframe+0x44/0xae

 Freed by task 1200:
  kasan_save_stack+0x1b/0x40
  kasan_set_track+0x1c/0x30
  kasan_set_free_info+0x20/0x30
  __kasan_slab_free+0xe5/0x110
  slab_free_freelist_hook+0x53/0x130
  kfree+0xcc/0x320
  smb2_ioctl_query_info+0x2ad/0x990
  cifs_ioctl+0xf18/0x16b0
  __x64_sys_ioctl+0xb9/0xf0
  do_syscall_64+0x33/0x40
  entry_SYSCALL_64_after_hwframe+0x44/0xae

 The buggy address belongs to the object at ffff888007b10c00
  which belongs to the cache kmalloc-512 of size 512
 The buggy address is located 0 bytes inside of
  512-byte region [ffff888007b10c00, ffff888007b10e00)
 The buggy address belongs to the page:
 page:0000000044e14b75 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b10
 head:0000000044e14b75 order:2 compound_mapcount:0 compound_pincount:0
 flags: 0x100000000010200(slab|head)
 raw: 0100000000010200 ffffea000015f500 0000000400000004 ffff888001042c80
 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
 page dumped because: kasan: bad access detected

 Memory state around the buggy address:
  ffff888007b10b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff888007b10b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 >ffff888007b10c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff888007b10c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff888007b10d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ==================================================================
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>