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x86/mm: Don't free P4D table when it is folded at runtime 

When the P4D page table layer is folded at runtime, the p4d_free()
should do nothing, the same as in <asm-generic/pgtable-nop4d.h>.

It seems this bug should cause double-free in efi_call_phys_epilog(),
but I don't know how to trigger that code path, so I can't confirm that
by testing.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # 4.17
Fixes: 98219dda2a ("x86/mm: Fold p4d page table layer at runtime")
Link: http://lkml.kernel.org/r/20180625102427.15015-1-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Andrey Ryabinin 2018-06-25 13:24:27 +03:00 committed by Ingo Molnar
parent 236f0cd286
commit 0e311d237d
1 changed files with 3 additions and 0 deletions
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3
arch/x86/include/asm/pgalloc.h
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@ -184,6 +184,9 @@ static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
{
if (!pgtable_l5_enabled())
return;
BUG_ON((unsigned long)p4d & (PAGE_SIZE-1));
free_page((unsigned long)p4d);
}