block: don't allow a disk link holder to itself

After creating a dm device, then user can reload such dm with itself,
and dead loop will be triggered because dm keep looking up to itself.

Test procedures:

1) dmsetup create test --table "xxx sda", assume dm-0 is created
2) dmsetup suspend test
3) dmsetup reload test --table "xxx dm-0"
4) dmsetup resume test

Test result:

BUG: TASK stack guard page was hit at 00000000736a261f (stack is 000000008d12c88d..00000000c8dd82d5)
stack guard page: 0000 [#1] PREEMPT SMP
CPU: 29 PID: 946 Comm: systemd-udevd Not tainted 6.1.0-rc3-next-20221101-00006-g17640ca3b0ee #1295
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
RIP: 0010:dm_prepare_ioctl+0xf/0x1e0
Code: da 48 83 05 4a 7c 99 0b 01 41 89 c4 eb cd e8 b8 1f 40 00 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 48 83 05 a1 5a 99 0b 01 <41> 56 49 89 d6 41 55 4c 8d af 90 02 00 00 9
RSP: 0018:ffffc90002090000 EFLAGS: 00010206
RAX: ffff8881049d6800 RBX: ffff88817e589000 RCX: 0000000000000000
RDX: ffffc90002090010 RSI: ffffc9000209001c RDI: ffff88817e589000
RBP: 00000000484a101d R08: 0000000000000000 R09: 0000000000000007
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000005331
R13: 0000000000005331 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fddf9609200(0000) GS:ffff889fbfd40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc9000208fff8 CR3: 0000000179043000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dm_blk_ioctl+0x50/0x1c0
 ? dm_prepare_ioctl+0xe0/0x1e0
 dm_blk_ioctl+0x88/0x1c0
 dm_blk_ioctl+0x88/0x1c0
 ......(a lot of same lines)
 dm_blk_ioctl+0x88/0x1c0
 dm_blk_ioctl+0x88/0x1c0
 blkdev_ioctl+0x184/0x3e0
 __x64_sys_ioctl+0xa3/0x110
 do_syscall_64+0x35/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fddf7306577
Code: b3 66 90 48 8b 05 11 89 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 88 8
RSP: 002b:00007ffd0b2ec318 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00005634ef478320 RCX: 00007fddf7306577
RDX: 0000000000000000 RSI: 0000000000005331 RDI: 0000000000000007
RBP: 0000000000000007 R08: 00005634ef4843e0 R09: 0000000000000080
R10: 00007fddf75cfb38 R11: 0000000000000246 R12: 00000000030d4000
R13: 0000000000000000 R14: 0000000000000000 R15: 00005634ef48b800
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dm_prepare_ioctl+0xf/0x1e0
Code: da 48 83 05 4a 7c 99 0b 01 41 89 c4 eb cd e8 b8 1f 40 00 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 48 83 05 a1 5a 99 0b 01 <41> 56 49 89 d6 41 55 4c 8d af 90 02 00 00 9
RSP: 0018:ffffc90002090000 EFLAGS: 00010206
RAX: ffff8881049d6800 RBX: ffff88817e589000 RCX: 0000000000000000
RDX: ffffc90002090010 RSI: ffffc9000209001c RDI: ffff88817e589000
RBP: 00000000484a101d R08: 0000000000000000 R09: 0000000000000007
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000005331
R13: 0000000000005331 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fddf9609200(0000) GS:ffff889fbfd40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc9000208fff8 CR3: 0000000179043000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Kernel panic - not syncing: Fatal exception in interrupt
Kernel Offset: disabled
---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---

Fix the problem by forbidding a disk to create link to itself.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221115141054.1051801-11-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/holder.c

@@ -65,6 +65,9 @@ int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
 	if (WARN_ON_ONCE(!disk->slave_dir))
 		return -EINVAL;
 
+	if (bdev->bd_disk == disk)
+		return -EINVAL;
+
 	/*
 	 * del_gendisk drops the initial reference to bd_holder_dir, so we
 	 * need to keep our own here to allow for cleanup past that point.