vfio/mdev: Fix a null-ptr-deref bug for mdev_unregister_parent()

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

vfio/mdev: Fix a null-ptr-deref bug for mdev_unregister_parent()

Inject fault while probing mdpy.ko, if kstrdup() of create_dir() fails in

kobject_add_internal() in kobject_init_and_add() in mdev_type_add()

in parent_create_sysfs_files(), it will return 0 and probe successfully.

And when rmmod mdpy.ko, the mdpy_dev_exit() will call

mdev_unregister_parent(), the mdev_type_remove() may traverse uninitialized

parent->types[i] in parent_remove_sysfs_files(), and it will cause

below null-ptr-deref.

If mdev_type_add() fails, return the error code and kset_unregister()

to fix the issue.

general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN

KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]

CPU: 2 PID: 10215 Comm: rmmod Tainted: G W N 6.6.0-rc2+ #20

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014

RIP: 0010:__kobject_del+0x62/0x1c0

Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 51 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 28 48 8d 7d 10 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 24 01 00 00 48 8b 75 10 48 89 df 48 8d 6b 3c e8

RSP: 0018:ffff88810695fd30 EFLAGS: 00010202

RAX: dffffc0000000000 RBX: ffffffffa0270268 RCX: 0000000000000000

RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000010

RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed10233a4ef1

R10: ffff888119d2778b R11: 0000000063666572 R12: 0000000000000000

R13: fffffbfff404e2d4 R14: dffffc0000000000 R15: ffffffffa0271660

FS: 00007fbc81981540(0000) GS:ffff888119d00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007fc14a142dc0 CR3: 0000000110a62003 CR4: 0000000000770ee0

DR0: ffffffff8fb0bce8 DR1: ffffffff8fb0bce9 DR2: ffffffff8fb0bcea

DR3: ffffffff8fb0bceb DR6: 00000000fffe0ff0 DR7: 0000000000000600

PKRU: 55555554

Call Trace:

<TASK>

? die_addr+0x3d/0xa0

? exc_general_protection+0x144/0x220

? asm_exc_general_protection+0x22/0x30

? __kobject_del+0x62/0x1c0

kobject_del+0x32/0x50

parent_remove_sysfs_files+0xd6/0x170 [mdev]

mdev_unregister_parent+0xfb/0x190 [mdev]

? mdev_register_parent+0x270/0x270 [mdev]

? find_module_all+0x9d/0xe0

mdpy_dev_exit+0x17/0x63 [mdpy]

__do_sys_delete_module.constprop.0+0x2fa/0x4b0

? module_flags+0x300/0x300

? __fput+0x4e7/0xa00

do_syscall_64+0x35/0x80

entry_SYSCALL_64_after_hwframe+0x46/0xb0

RIP: 0033:0x7fbc813221b7

Code: 73 01 c3 48 8b 0d d1 8c 2c 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 b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 8c 2c 00 f7 d8 64 89 01 48

RSP: 002b:00007ffe780e0648 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0

RAX: ffffffffffffffda RBX: 00007ffe780e06a8 RCX: 00007fbc813221b7

RDX: 000000000000000a RSI: 0000000000000800 RDI: 000055e214df9b58

RBP: 000055e214df9af0 R08: 00007ffe780df5c1 R09: 0000000000000000

R10: 00007fbc8139ecc0 R11: 0000000000000206 R12: 00007ffe780e0870

R13: 00007ffe780e0ed0 R14: 000055e214df9260 R15: 000055e214df9af0

</TASK>

Modules linked in: mdpy(-) mdev vfio_iommu_type1 vfio [last unloaded: mdpy]

Dumping ftrace buffer:

(ftrace buffer empty)

---[ end trace 0000000000000000 ]---

RIP: 0010:__kobject_del+0x62/0x1c0

Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 51 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 6b 28 48 8d 7d 10 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 24 01 00 00 48 8b 75 10 48 89 df 48 8d 6b 3c e8

RSP: 0018:ffff88810695fd30 EFLAGS: 00010202

RAX: dffffc0000000000 RBX: ffffffffa0270268 RCX: 0000000000000000

RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000010

RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed10233a4ef1

R10: ffff888119d2778b R11: 0000000063666572 R12: 0000000000000000

R13: fffffbfff404e2d4 R14: dffffc0000000000 R15: ffffffffa0271660

FS: 00007fbc81981540(0000) GS:ffff888119d00000(000

---truncated---