mm/memory-failure.c: catch unexpected -EFAULT from vma_address()

It's unexpected to walk the page table when vma_address() return
-EFAULT.  But dev_pagemap_mapping_shift() is called only when vma
associated to the error page is found already in
collect_procs_{file,anon}, so vma_address() should not return -EFAULT
except with some bug, as Naoya pointed out.  We can use VM_BUG_ON_VMA()
to catch this bug here.

Link: https://lkml.kernel.org/r/20220218090118.1105-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 1e1cb11..b5291c8 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -315,6 +315,7 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
        pmd_t *pmd;
        pte_t *pte;
 
+       VM_BUG_ON_VMA(address == -EFAULT, vma);
        pgd = pgd_offset(vma->vm_mm, address);
        if (!pgd_present(*pgd))
                return 0;