4.17-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andrey Ryabinin <[email protected]> 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 <[email protected]> Reviewed-by: Kirill A. Shutemov <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] # 4.17 Fixes: 98219dda2ab5 ("x86/mm: Fold p4d page table layer at runtime") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Andrey Ryabinin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/include/asm/pgalloc.h | 3 +++ 1 file changed, 3 insertions(+) --- 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(struc 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); }
