[PATCH] mm: fix kernel NULL pointer dereference in page_vma_mapped_walk

[zhenwei pi]

size_to_hstate(4K) returns NULL pointer, this leads kernel BUG in
function page_vma_mapped_walk.

 BUG: kernel NULL pointer dereference, address: 0000000000000028
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 102a8b067 P4D 102a8b067 PUD 102a88067 PMD 0
 Oops: 0000 [#1] PREEMPT SMP NOPTI
 CPU: 0 PID: 16 Comm: kworker/0:1 Kdump: loaded Tainted: G   M        E     5.18.0-rc1.bm.1-amd64 #3
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
 Workqueue: events mce_gen_pool_process
 RIP: 0010:page_vma_mapped_walk+0x4aa/0x850
 Code: 8b 77 20 48 89 c2 4c 89 ef e8 b2 c4 02 00 49 89 c4 48 89 43 30 48 85 c0 0f 84 a7 fd ff ff 48 89 ef e8 fa 9c 02 00 49 8d 7d 74 <83> 78 28 09 0f 84 1e 03 00 00 48 89 7b 38 e8 a3 cc 60 00 48 89 df
 RSP: 0018:ffffc9000008bc58 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: ffffc9000008bca0 RCX: 0000000000000009
 RDX: 0000000000200000 RSI: ffffffff82b4a460 RDI: ffff88810ac5c3f4
 RBP: 0000000000001000 R08: 0000000000001000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000007 R12: ffff888072cafd10
 R13: ffff88810ac5c380 R14: ffff888101afc440 R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff88823fc00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000028 CR3: 0000000106ca2002 CR4: 0000000000772ef0
 PKRU: 55555554
 Call Trace:
  <TASK>
  ? preempt_count_add+0x68/0xa0
  page_mapped_in_vma+0xb4/0x230
  collect_procs.part.35+0x11b/0x440
  hwpoison_user_mappings+0x165/0x5b0
  ? zone_pcp_enable+0x16/0x30
  memory_failure+0xbea/0xd90
  ? _printk+0x58/0x6f
  uc_decode_notifier+0x4b/0xd0
  blocking_notifier_call_chain+0x60/0x90
  mce_gen_pool_process+0x3c/0x60
  process_one_work+0x1c2/0x390
  ? process_one_work+0x390/0x390
  worker_thread+0x30/0x360
  ? process_one_work+0x390/0x390
  kthread+0xe6/0x110
  ? kthread_complete_and_exit+0x20/0x20
  ret_from_fork+0x1f/0x30
  </TASK>

Fixes: 2aff7a4755bed ("mm: Convert page_vma_mapped_walk to work on PFNs")
Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
---
 mm/page_vma_mapped.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 1187f9c1ec5b..a39ec23581c9 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -163,7 +163,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 		return not_found(pvmw);
 
 	if (unlikely(is_vm_hugetlb_page(vma))) {
-		unsigned long size = pvmw->nr_pages * PAGE_SIZE;
+		unsigned long size = huge_page_size(hstate_vma(vma));
 		/* The only possible mapping was handled on last iteration */
 		if (pvmw->pte)
 			return not_found(pvmw);
-- 
2.25.1