From: "gregkh@linuxfoundation.org" gregkh@linuxfoundation.org
commit 0e311d237d7f3022b7dafb639b42541bfb42fe94 upstream.
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: 98219dda2ab5 ("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 Signed-off-by: Andrey Ryabinin aryabinin@virtuozzo.com --- arch/x86/include/asm/pgalloc.h | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h index 263c142a6a6c..f65e9e1cea4c 100644 --- a/arch/x86/include/asm/pgalloc.h +++ b/arch/x86/include/asm/pgalloc.h @@ -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); }