powerpc/pseries/vas: Add close() callback in vas_vm_ops struct

powerpc/pseries/vas: Add close() callback in vas_vm_ops struct

[ Upstream commit 05aa156e156ef3168e7ab8a68721945196495c17 ]

The mapping VMA address is saved in VAS window struct when the
paste address is mapped. This VMA address is used during migration
to unmap the paste address if the window is active. The paste
address mapping will be removed when the window is closed or with
the munmap(). But the VMA address in the VAS window is not updated
with munmap() which is causing invalid access during migration.

The KASAN report shows:
[16386.254991] BUG: KASAN: slab-use-after-free in reconfig_close_windows+0x1a0/0x4e8
[16386.255043] Read of size 8 at addr c00000014a819670 by task drmgr/696928

[16386.255096] CPU: 29 UID: 0 PID: 696928 Comm: drmgr Kdump: loaded Tainted: G    B              6.11.0-rc5-nxgzip #2
[16386.255128] Tainted: [B]=BAD_PAGE
[16386.255148] Hardware name: IBM,9080-HEX Power11 (architected) 0x820200 0xf000007 of:IBM,FW1110.00 (NH1110_016) hv:phyp pSeries
[16386.255181] Call Trace:
[16386.255202] [c00000016b297660] [c0000000018ad0ac] dump_stack_lvl+0x84/0xe8 (unreliable)
[16386.255246] [c00000016b297690] [c0000000006e8a90] print_report+0x19c/0x764
[16386.255285] [c00000016b297760] [c0000000006e9490] kasan_report+0x128/0x1f8
[16386.255309] [c00000016b297880] [c0000000006eb5c8] __asan_load8+0xac/0xe0
[16386.255326] [c00000016b2978a0] [c00000000013f898] reconfig_close_windows+0x1a0/0x4e8
[16386.255343] [c00000016b297990] [c000000000140e58] vas_migration_handler+0x3a4/0x3fc
[16386.255368] [c00000016b297a90] [c000000000128848] pseries_migrate_partition+0x4c/0x4c4
...

[16386.256136] Allocated by task 696554 on cpu 31 at 16377.277618s:
[16386.256149]  kasan_save_stack+0x34/0x68
[16386.256163]  kasan_save_track+0x34/0x80
[16386.256175]  kasan_save_alloc_info+0x58/0x74
[16386.256196]  __kasan_slab_alloc+0xb8/0xdc
[16386.256209]  kmem_cache_alloc_noprof+0x200/0x3d0
[16386.256225]  vm_area_alloc+0x44/0x150
[16386.256245]  mmap_region+0x214/0x10c4
[16386.256265]  do_mmap+0x5fc/0x750
[16386.256277]  vm_mmap_pgoff+0x14c/0x24c
[16386.256292]  ksys_mmap_pgoff+0x20c/0x348
[16386.256303]  sys_mmap+0xd0/0x160
...

[16386.256350] Freed by task 0 on cpu 31 at 16386.204848s:
[16386.256363]  kasan_save_stack+0x34/0x68
[16386.256374]  kasan_save_track+0x34/0x80
[16386.256384]  kasan_save_free_info+0x64/0x10c
[16386.256396]  __kasan_slab_free+0x120/0x204
[16386.256415]  kmem_cache_free+0x128/0x450
[16386.256428]  vm_area_free_rcu_cb+0xa8/0xd8
[16386.256441]  rcu_do_batch+0x2c8/0xcf0
[16386.256458]  rcu_core+0x378/0x3c4
[16386.256473]  handle_softirqs+0x20c/0x60c
[16386.256495]  do_softirq_own_stack+0x6c/0x88
[16386.256509]  do_softirq_own_stack+0x58/0x88
[16386.256521]  __irq_exit_rcu+0x1a4/0x20c
[16386.256533]  irq_exit+0x20/0x38
[16386.256544]  interrupt_async_exit_prepare.constprop.0+0x18/0x2c
...

[16386.256717] Last potentially related work creation:
[16386.256729]  kasan_save_stack+0x34/0x68
[16386.256741]  __kasan_record_aux_stack+0xcc/0x12c
[16386.256753]  __call_rcu_common.constprop.0+0x94/0xd04
[16386.256766]  vm_area_free+0x28/0x3c
[16386.256778]  remove_vma+0xf4/0x114
[16386.256797]  do_vmi_align_munmap.constprop.0+0x684/0x870
[16386.256811]  __vm_munmap+0xe0/0x1f8
[16386.256821]  sys_munmap+0x54/0x6c
[16386.256830]  system_call_exception+0x1a0/0x4a0
[16386.256841]  system_call_vectored_common+0x15c/0x2ec

[16386.256868] The buggy address belongs to the object at c00000014a819670
                which belongs to the cache vm_area_struct of size 168
[16386.256887] The buggy address is located 0 bytes inside of
                freed 168-byte region [c00000014a819670, c00000014a819718)

[16386.256915] The buggy address belongs to the physical page:
[16386.256928] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14a81
[16386.256950] memcg:c0000000ba430001
[16386.256961] anon flags: 0x43ffff800000000(node=4|zone=0|lastcpupid=0x7ffff)
[16386.256975] page_type: 0xfdffffff(slab)
[16386.256990] raw: 043ffff800000000 c00000000501c080 0000000000000000 5deadbee00000001
[16386.257003] raw: 0000000000000000 00000000011a011a 00000001fdffffff c0000000ba430001
[16386.257018] page dumped because: kasan: bad access detected

This patch adds close() callback in vas_vm_ops vm_operations_struct
which will be executed during munmap() before freeing VMA. The VMA
address in the VAS window is set to NULL after holding the window
mmap_mutex.

Fixes: 37e6764895ef ("powerpc/pseries/vas: Add VAS migration handler")
Signed-off-by: Haren Myneni <haren@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20241214051758.997759-1-haren@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>