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mm: abstract moving to the next PFN 

In order to fix the L1TF vulnerability, x86 can invert the PTE bits for
PROT_NONE VMAs, which means we cannot move from one PTE to the next by
adding 1 to the PFN field of the PTE.  This results in the BUG reported at
[1].

Abstract advancing the PTE to the next PFN through a pte_next_pfn()
function/macro.

Link: https://lkml.kernel.org/r/20230920040958.866520-1-willy@infradead.org
Fixes: bcc6cc8325 ("mm: add default definition of set_ptes()")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: syzbot+55cc72f8cc3a549119df@syzkaller.appspotmail.com
Closes: https://lkml.kernel.org/r/000000000000d099fa0604f03351@google.com [1]
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-09-20 05:09:58 +01:00 committed by Andrew Morton
parent a501a07030
commit ce60f27bb6
2 changed files with 17 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/include/asm/pgtable.h
View File

@ -955,6 +955,14 @@ static inline int pte_same(pte_t a, pte_t b)
return a.pte == b.pte;
}
static inline pte_t pte_next_pfn(pte_t pte)
{
if (__pte_needs_invert(pte_val(pte)))
return __pte(pte_val(pte) - (1UL << PFN_PTE_SHIFT));
return __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
}
#define pte_next_pfn pte_next_pfn
static inline int pte_present(pte_t a)
{
return pte_flags(a) & (_PAGE_PRESENT | _PAGE_PROTNONE);

10
include/linux/pgtable.h
View File

@ -206,6 +206,14 @@ static inline int pmd_young(pmd_t pmd)
#endif
#ifndef set_ptes
#ifndef pte_next_pfn
static inline pte_t pte_next_pfn(pte_t pte)
{
return __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
}
#endif
/**
* set_ptes - Map consecutive pages to a contiguous range of addresses.
* @mm: Address space to map the pages into.
@ -231,7 +239,7 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
if (--nr == 0)
break;
ptep++;
pte = __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
pte = pte_next_pfn(pte);
}
arch_leave_lazy_mmu_mode();
}