fs/ntfs3: Add null pointer check to attr_load_runs_vcn

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

fs/ntfs3: Add null pointer check to attr_load_runs_vcn

Some metadata files are handled before MFT. This adds a null pointer
check for some corner cases that could lead to NPD while reading these
metadata files for a malformed NTFS image.

[ 240.190827] BUG: kernel NULL pointer dereference, address: 0000000000000158
[ 240.191583] #PF: supervisor read access in kernel mode
[ 240.191956] #PF: error_code(0x0000) - not-present page
[ 240.192391] PGD 0 P4D 0
[ 240.192897] Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
[ 240.193805] CPU: 0 PID: 242 Comm: mount Tainted: G B 5.19.0+ #17
[ 240.194477] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 240.195152] RIP: 0010:ni_find_attr+0xae/0x300
[ 240.195679] Code: c8 48 c7 45 88 c0 4e 5e 86 c7 00 f1 f1 f1 f1 c7 40 04 00 f3 f3 f3 65 48 8b 04 25 28 00 00 00 48 89 45 d0 31 c0 e8 e2 d9f
[ 240.196642] RSP: 0018:ffff88800812f690 EFLAGS: 00000286
[ 240.197019] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff85ef037a
[ 240.197523] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffff88e95f60
[ 240.197877] RBP: ffff88800812f738 R08: 0000000000000001 R09: fffffbfff11d2bed
[ 240.198292] R10: ffffffff88e95f67 R11: fffffbfff11d2bec R12: 0000000000000000
[ 240.198647] R13: 0000000000000080 R14: 0000000000000000 R15: 0000000000000000
[ 240.199410] FS: 00007f233c33be40(0000) GS:ffff888058200000(0000) knlGS:0000000000000000
[ 240.199895] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 240.200314] CR2: 0000000000000158 CR3: 0000000004d32000 CR4: 00000000000006f0
[ 240.200839] Call Trace:
[ 240.201104] <TASK>
[ 240.201502] ? ni_load_mi+0x80/0x80
[ 240.202297] ? ___slab_alloc+0x465/0x830
[ 240.202614] attr_load_runs_vcn+0x8c/0x1a0
[ 240.202886] ? __kasan_slab_alloc+0x32/0x90
[ 240.203157] ? attr_data_write_resident+0x250/0x250
[ 240.203543] mi_read+0x133/0x2c0
[ 240.203785] mi_get+0x70/0x140
[ 240.204012] ni_load_mi_ex+0xfa/0x190
[ 240.204346] ? ni_std5+0x90/0x90
[ 240.204588] ? __kasan_kmalloc+0x88/0xb0
[ 240.204859] ni_enum_attr_ex+0xf1/0x1c0
[ 240.205107] ? ni_fname_type.part.0+0xd0/0xd0
[ 240.205600] ? ntfs_load_attr_list+0xbe/0x300
[ 240.205864] ? ntfs_cmp_names_cpu+0x125/0x180
[ 240.206157] ntfs_iget5+0x56c/0x1870
[ 240.206510] ? ntfs_get_block_bmap+0x70/0x70
[ 240.206776] ? __kasan_kmalloc+0x88/0xb0
[ 240.207030] ? set_blocksize+0x95/0x150
[ 240.207545] ntfs_fill_super+0xb8f/0x1e20
[ 240.207839] ? put_ntfs+0x1d0/0x1d0
[ 240.208069] ? vsprintf+0x20/0x20
[ 240.208467] ? mutex_unlock+0x81/0xd0
[ 240.208846] ? set_blocksize+0x95/0x150
[ 240.209221] get_tree_bdev+0x232/0x370
[ 240.209804] ? put_ntfs+0x1d0/0x1d0
[ 240.210519] ntfs_fs_get_tree+0x15/0x20
[ 240.210991] vfs_get_tree+0x4c/0x130
[ 240.211455] path_mount+0x645/0xfd0
[ 240.211806] ? putname+0x80/0xa0
[ 240.212112] ? finish_automount+0x2e0/0x2e0
[ 240.212559] ? kmem_cache_free+0x110/0x390
[ 240.212906] ? putname+0x80/0xa0
[ 240.213329] do_mount+0xd6/0xf0
[ 240.213829] ? path_mount+0xfd0/0xfd0
[ 240.214246] ? __kasan_check_write+0x14/0x20
[ 240.214774] __x64_sys_mount+0xca/0x110
[ 240.215080] do_syscall_64+0x3b/0x90
[ 240.215442] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 240.215811] RIP: 0033:0x7f233b4e948a
[ 240.216104] 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
[ 240.217615] RSP: 002b:00007fff02211ec8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
[ 240.218718] RAX: ffffffffffffffda RBX: 0000561cdc35b060 RCX: 00007f233b4e948a
[ 240.219556] RDX: 0000561cdc35b260 RSI: 0000561cdc35b2e0 RDI: 0000561cdc363af0
[ 240.219975] RBP: 0000000000000000 R08: 0000561cdc35b280 R09: 0000000000000020
[ 240.220403] R10: 00000000c0ed0000 R11: 0000000000000202 R12: 0000561cdc363af0
[ 240.220803] R13: 000
---truncated---