md-raid10: fix KASAN warning

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

md-raid10: fix KASAN warning

There's a KASAN warning in raid10_remove_disk when running the lvm
test lvconvert-raid-reshape.sh. We fix this warning by verifying that the
value "number" is valid.

BUG: KASAN: slab-out-of-bounds in raid10_remove_disk+0x61/0x2a0 [raid10]
Read of size 8 at addr ffff889108f3d300 by task mdX_raid10/124682

CPU: 3 PID: 124682 Comm: mdX_raid10 Not tainted 5.19.0-rc6 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
print_report.cold+0x45/0x57a
? __lock_text_start+0x18/0x18
? raid10_remove_disk+0x61/0x2a0 [raid10]
kasan_report+0xa8/0xe0
? raid10_remove_disk+0x61/0x2a0 [raid10]
raid10_remove_disk+0x61/0x2a0 [raid10]
Buffer I/O error on dev dm-76, logical block 15344, async page read
? __mutex_unlock_slowpath.constprop.0+0x1e0/0x1e0
remove_and_add_spares+0x367/0x8a0 [md_mod]
? super_written+0x1c0/0x1c0 [md_mod]
? mutex_trylock+0xac/0x120
? _raw_spin_lock+0x72/0xc0
? _raw_spin_lock_bh+0xc0/0xc0
md_check_recovery+0x848/0x960 [md_mod]
raid10d+0xcf/0x3360 [raid10]
? sched_clock_cpu+0x185/0x1a0
? rb_erase+0x4d4/0x620
? var_wake_function+0xe0/0xe0
? psi_group_change+0x411/0x500
? preempt_count_sub+0xf/0xc0
? _raw_spin_lock_irqsave+0x78/0xc0
? __lock_text_start+0x18/0x18
? raid10_sync_request+0x36c0/0x36c0 [raid10]
? preempt_count_sub+0xf/0xc0
? _raw_spin_unlock_irqrestore+0x19/0x40
? del_timer_sync+0xa9/0x100
? try_to_del_timer_sync+0xc0/0xc0
? _raw_spin_lock_irqsave+0x78/0xc0
? __lock_text_start+0x18/0x18
? _raw_spin_unlock_irq+0x11/0x24
? __list_del_entry_valid+0x68/0xa0
? finish_wait+0xa3/0x100
md_thread+0x161/0x260 [md_mod]
? unregister_md_personality+0xa0/0xa0 [md_mod]
? _raw_spin_lock_irqsave+0x78/0xc0
? prepare_to_wait_event+0x2c0/0x2c0
? unregister_md_personality+0xa0/0xa0 [md_mod]
kthread+0x148/0x180
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
</TASK>

Allocated by task 124495:
kasan_save_stack+0x1e/0x40
__kasan_kmalloc+0x80/0xa0
setup_conf+0x140/0x5c0 [raid10]
raid10_run+0x4cd/0x740 [raid10]
md_run+0x6f9/0x1300 [md_mod]
raid_ctr+0x2531/0x4ac0 [dm_raid]
dm_table_add_target+0x2b0/0x620 [dm_mod]
table_load+0x1c8/0x400 [dm_mod]
ctl_ioctl+0x29e/0x560 [dm_mod]
dm_compat_ctl_ioctl+0x7/0x20 [dm_mod]
__do_compat_sys_ioctl+0xfa/0x160
do_syscall_64+0x90/0xc0
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Last potentially related work creation:
kasan_save_stack+0x1e/0x40
__kasan_record_aux_stack+0x9e/0xc0
kvfree_call_rcu+0x84/0x480
timerfd_release+0x82/0x140
L __fput+0xfa/0x400
task_work_run+0x80/0xc0
exit_to_user_mode_prepare+0x155/0x160
syscall_exit_to_user_mode+0x12/0x40
do_syscall_64+0x42/0xc0
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Second to last potentially related work creation:
kasan_save_stack+0x1e/0x40
__kasan_record_aux_stack+0x9e/0xc0
kvfree_call_rcu+0x84/0x480
timerfd_release+0x82/0x140
__fput+0xfa/0x400
task_work_run+0x80/0xc0
exit_to_user_mode_prepare+0x155/0x160
syscall_exit_to_user_mode+0x12/0x40
do_syscall_64+0x42/0xc0
entry_SYSCALL_64_after_hwframe+0x46/0xb0

The buggy address belongs to the object at ffff889108f3d200
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 0 bytes to the right of
256-byte region [ffff889108f3d200, ffff889108f3d300)

The buggy address belongs to the physical page:
page:000000007ef2a34c refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1108f3c
head:000000007ef2a34c order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=2)
raw: 4000000000010200 0000000000000000 dead000000000001 ffff889100042b40
raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff889108f3d200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff889108f3d280: 00 00
---truncated---