mm/vmalloc: fix data race in show_numa_info()

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

mm/vmalloc: fix data race in show_numa_info()

The following data-race was found in show_numa_info():

==================================================================

BUG: KCSAN: data-race in vmalloc_info_show / vmalloc_info_show

read to 0xffff88800971fe30 of 4 bytes by task 8289 on cpu 0:

show_numa_info mm/vmalloc.c:4936 [inline]

vmalloc_info_show+0x5a8/0x7e0 mm/vmalloc.c:5016

seq_read_iter+0x373/0xb40 fs/seq_file.c:230

proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299

....

write to 0xffff88800971fe30 of 4 bytes by task 8287 on cpu 1:

show_numa_info mm/vmalloc.c:4934 [inline]

vmalloc_info_show+0x38f/0x7e0 mm/vmalloc.c:5016

seq_read_iter+0x373/0xb40 fs/seq_file.c:230

proc_reg_read_iter+0x11e/0x170 fs/proc/inode.c:299

....

value changed: 0x0000008f -> 0x00000000

==================================================================

According to this report,there is a read/write data-race because

m->private is accessible to multiple CPUs. To fix this, instead of

allocating the heap in proc_vmalloc_init() and passing the heap address to

m->private, vmalloc_info_show() should allocate the heap.