fs/ntfs3: Add null pointer check for inode operations

In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: Add null pointer check for inode operations

This adds a sanity check for the i_op pointer of the inode which is
returned after reading Root directory MFT record. We should check the
i_op is valid before trying to create the root dentry, otherwise we may
encounter a NPD while mounting a image with a funny Root directory MFT
record.

[ 114.484325] BUG: kernel NULL pointer dereference, address: 0000000000000008
[ 114.484811] #PF: supervisor read access in kernel mode
[ 114.485084] #PF: error_code(0x0000) - not-present page
[ 114.485606] PGD 0 P4D 0
[ 114.485975] Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
[ 114.486570] CPU: 0 PID: 237 Comm: mount Tainted: G B 6.0.0-rc4 #28
[ 114.486977] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 114.488169] RIP: 0010:d_flags_for_inode+0xe0/0x110
[ 114.488816] Code: 24 f7 ff 49 83 3e 00 74 41 41 83 cd 02 66 44 89 6b 02 eb 92 48 8d 7b 20 e8 6d 24 f7 ff 4c 8b 73 20 49 8d 7e 08 e8 60 241
[ 114.490326] RSP: 0018:ffff8880065e7aa8 EFLAGS: 00000296
[ 114.490695] RAX: 0000000000000001 RBX: ffff888008ccd750 RCX: ffffffff84af2aea
[ 114.490986] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffff87abd020
[ 114.491364] RBP: ffff8880065e7ac8 R08: 0000000000000001 R09: fffffbfff0f57a05
[ 114.491675] R10: ffffffff87abd027 R11: fffffbfff0f57a04 R12: 0000000000000000
[ 114.491954] R13: 0000000000000008 R14: 0000000000000000 R15: ffff888008ccd750
[ 114.492397] FS: 00007fdc8a627e40(0000) GS:ffff888058200000(0000) knlGS:0000000000000000
[ 114.492797] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 114.493150] CR2: 0000000000000008 CR3: 00000000013ba000 CR4: 00000000000006f0
[ 114.493671] Call Trace:
[ 114.493890] <TASK>
[ 114.494075] __d_instantiate+0x24/0x1c0
[ 114.494505] d_instantiate.part.0+0x35/0x50
[ 114.494754] d_make_root+0x53/0x80
[ 114.494998] ntfs_fill_super+0x1232/0x1b50
[ 114.495260] ? put_ntfs+0x1d0/0x1d0
[ 114.495499] ? vsprintf+0x20/0x20
[ 114.495723] ? set_blocksize+0x95/0x150
[ 114.495964] get_tree_bdev+0x232/0x370
[ 114.496272] ? put_ntfs+0x1d0/0x1d0
[ 114.496502] ntfs_fs_get_tree+0x15/0x20
[ 114.496859] vfs_get_tree+0x4c/0x130
[ 114.497099] path_mount+0x654/0xfe0
[ 114.497507] ? putname+0x80/0xa0
[ 114.497933] ? finish_automount+0x2e0/0x2e0
[ 114.498362] ? putname+0x80/0xa0
[ 114.498571] ? kmem_cache_free+0x1c4/0x440
[ 114.498819] ? putname+0x80/0xa0
[ 114.499069] do_mount+0xd6/0xf0
[ 114.499343] ? path_mount+0xfe0/0xfe0
[ 114.499683] ? __kasan_check_write+0x14/0x20
[ 114.500133] __x64_sys_mount+0xca/0x110
[ 114.500592] do_syscall_64+0x3b/0x90
[ 114.500930] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 114.501294] RIP: 0033:0x7fdc898e948a
[ 114.501542] Code: 48 8b 0d 11 fa 2a 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 008
[ 114.502716] RSP: 002b:00007ffd793e58f8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
[ 114.503175] RAX: ffffffffffffffda RBX: 0000564b2228f060 RCX: 00007fdc898e948a
[ 114.503588] RDX: 0000564b2228f260 RSI: 0000564b2228f2e0 RDI: 0000564b22297ce0
[ 114.504925] RBP: 0000000000000000 R08: 0000564b2228f280 R09: 0000000000000020
[ 114.505484] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000564b22297ce0
[ 114.505823] R13: 0000564b2228f260 R14: 0000000000000000 R15: 00000000ffffffff
[ 114.506562] </TASK>
[ 114.506887] Modules linked in:
[ 114.507648] CR2: 0000000000000008
[ 114.508884] ---[ end trace 0000000000000000 ]---
[ 114.509675] RIP: 0010:d_flags_for_inode+0xe0/0x110
[ 114.510140] Code: 24 f7 ff 49 83 3e 00 74 41 41 83 cd 02 66 44 89 6b 02 eb 92 48 8d 7b 20 e8 6d 24 f7 ff 4c 8b 73 20 49 8d 7e 08 e8 60 241
[ 114.511762] RSP: 0018:ffff8880065e7aa8 EFLAGS: 00000296
[ 114.512401] RAX: 0000000000000001 RBX: ffff888008ccd750 RCX: ffffffff84af2aea
[ 114.51
---truncated---