From e6ab9c4d437764c7fb728d428dc9e717cdb183d0 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Tue, 25 Apr 2017 12:25:57 +0300 Subject: [PATCH] x86/mm/64: Fix crash in remove_pagetable() remove_pagetable() does page walk using p*d_page_vaddr() plus cast. It's not canonical approach -- we usually use p*d_offset() for that. It works fine as long as all page table levels are present. We broke the invariant by introducing folded p4d page table level. As result, remove_pagetable() interprets PMD as PUD and it leads to crash: BUG: unable to handle kernel paging request at ffff880300000000 IP: memchr_inv+0x60/0x110 PGD 317d067 P4D 317d067 PUD 3180067 PMD 33f102067 PTE 8000000300000060 Let's fix this by using p*d_offset() instead of p*d_page_vaddr() for page walk. Reported-by: Dan Williams Tested-by: Dan Williams Signed-off-by: Kirill A. Shutemov Cc: Andy Lutomirski Cc: Dave Hansen Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-mm@kvack.org Fixes: f2a6a7050109 ("x86: Convert the rest of the code to support p4d_t") Link: http://lkml.kernel.org/r/20170425092557.21852-1-kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/mm/init_64.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index a242139df8fe..745e5e183169 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -962,7 +962,7 @@ remove_pud_table(pud_t *pud_start, unsigned long addr, unsigned long end, continue; } - pmd_base = (pmd_t *)pud_page_vaddr(*pud); + pmd_base = pmd_offset(pud, 0); remove_pmd_table(pmd_base, addr, next, direct); free_pmd_table(pmd_base, pud); } @@ -988,7 +988,7 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end, BUILD_BUG_ON(p4d_large(*p4d)); - pud_base = (pud_t *)p4d_page_vaddr(*p4d); + pud_base = pud_offset(p4d, 0); remove_pud_table(pud_base, addr, next, direct); free_pud_table(pud_base, p4d); } @@ -1013,7 +1013,7 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct) if (!pgd_present(*pgd)) continue; - p4d = (p4d_t *)pgd_page_vaddr(*pgd); + p4d = p4d_offset(pgd, 0); remove_p4d_table(p4d, addr, next, direct); }