Hi, On Fri, Apr 20, 2018 at 03:20:21PM -0700, Dave Hansen wrote: > The pageattr.c code attempts to process "faults" when it goes looking > for PTEs to change and finds non-present entries. It allows these > faults in the linear map which is "expected to have holes", but > WARN()s about them elsewhere, like when called on the kernel image. > > However, we are now calling change_page_attr_clear() on the kernel > image in the process of trying to clear the Global bit. > > This trips the warning in __cpa_process_fault() if a non-present PTE is > encountered in the kernel image. The "holes" in the kernel image > result from free_init_pages()'s use of set_memory_np(). These holes > are totally fine, and result from normal operation, just as they would > be in the kernel linear map. > > Just silence the warning when holes in the kernel image are encountered. > > Signed-off-by: Dave Hansen <[email protected]> > Fixes: 39114b7a7 (x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel > image) > Reported-by: Mariusz Ceier <[email protected]> > Reported-by: Aaro Koskinen <[email protected]>
Tested-by: Aaro Koskinen <[email protected]> A. > Cc: Andrea Arcangeli <[email protected]> > Cc: Andy Lutomirski <[email protected]> > Cc: Arjan van de Ven <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Dan Williams <[email protected]> > Cc: David Woodhouse <[email protected]> > Cc: Greg Kroah-Hartman <[email protected]> > Cc: Hugh Dickins <[email protected]> > Cc: Josh Poimboeuf <[email protected]> > Cc: Juergen Gross <[email protected]> > Cc: Kees Cook <[email protected]> > Cc: Linus Torvalds <[email protected]> > Cc: Nadav Amit <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: [email protected] > --- > > b/arch/x86/mm/pageattr.c | 41 +++++++++++++++++++++++++++++++---------- > 1 file changed, 31 insertions(+), 10 deletions(-) > > diff -puN arch/x86/mm/pageattr.c~pti-glb-warning-inpageattr > arch/x86/mm/pageattr.c > --- a/arch/x86/mm/pageattr.c~pti-glb-warning-inpageattr 2018-04-20 > 14:10:01.619749168 -0700 > +++ b/arch/x86/mm/pageattr.c 2018-04-20 14:10:01.623749168 -0700 > @@ -93,6 +93,18 @@ void arch_report_meminfo(struct seq_file > static inline void split_page_count(int level) { } > #endif > > +static inline int > +within(unsigned long addr, unsigned long start, unsigned long end) > +{ > + return addr >= start && addr < end; > +} > + > +static inline int > +within_inclusive(unsigned long addr, unsigned long start, unsigned long end) > +{ > + return addr >= start && addr <= end; > +} > + > #ifdef CONFIG_X86_64 > > static inline unsigned long highmap_start_pfn(void) > @@ -106,20 +118,26 @@ static inline unsigned long highmap_end_ > return __pa_symbol(roundup(_brk_end, PMD_SIZE) - 1) >> PAGE_SHIFT; > } > > -#endif > - > -static inline int > -within(unsigned long addr, unsigned long start, unsigned long end) > +static bool __cpa_pfn_in_highmap(unsigned long pfn) > { > - return addr >= start && addr < end; > + /* > + * Kernel text has an alias mapping at a high address, known > + * here as "highmap". > + */ > + return within_inclusive(pfn, highmap_start_pfn(), > + highmap_end_pfn()); > } > > -static inline int > -within_inclusive(unsigned long addr, unsigned long start, unsigned long end) > +#else > + > +static bool __cpa_pfn_in_highmap(unsigned long pfn) > { > - return addr >= start && addr <= end; > + /* There is no highmap on 32-bit */ > + return false; > } > > +#endif > + > /* > * Flushing functions > */ > @@ -1183,6 +1201,10 @@ static int __cpa_process_fault(struct cp > cpa->numpages = 1; > cpa->pfn = __pa(vaddr) >> PAGE_SHIFT; > return 0; > + > + } else if (__cpa_pfn_in_highmap(cpa->pfn)) { > + /* Faults in the highmap are OK, so do not warn: */ > + return -EFAULT; > } else { > WARN(1, KERN_WARNING "CPA: called for zero pte. " > "vaddr = %lx cpa->vaddr = %lx\n", vaddr, > @@ -1335,8 +1357,7 @@ static int cpa_process_alias(struct cpa_ > * to touch the high mapped kernel as well: > */ > if (!within(vaddr, (unsigned long)_text, _brk_end) && > - within_inclusive(cpa->pfn, highmap_start_pfn(), > - highmap_end_pfn())) { > + __cpa_pfn_in_highmap(cpa->pfn)) { > unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) + > __START_KERNEL_map - phys_base; > alias_cpa = *cpa; > _
