Messages in this thread | | | Date | Fri, 12 Aug 2016 14:12:33 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v3 50/51] x86/mm: move arch_within_stack_frames() to usercopy.c |
| |
On Fri, Aug 12, 2016 at 10:36:21AM -0700, Kees Cook wrote: > On Fri, Aug 12, 2016 at 7:29 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > When I tried to port arch_within_stack_frames() to use the new unwinder, > > I got a nightmare include file "header soup" scenario when unwind.h was > > included from thread_info.h. And anyway, I think thread_info.h isn't > > really an appropriate place for this function. So move it to usercopy.c > > instead. > > > > Since it relies on its parent's stack pointer, and the function is no > > longer inlined, the arguments to the __builtin_frame_address() calls > > have been incremented. > > Cool, looks good (minor change noted below). This patch might be a > good place to drop this from mm/Makefile too: > > # Since __builtin_frame_address does work as used, disable the warning. > CFLAGS_usercopy.o += $(call cc-disable-warning, frame-address) > > Since frame-address warnings have been disabled globally now since > commit 124a3d88fa20 ("Disable "frame-address" warning").
Ok, I'll do that with the next patch (51/51) which removes the __builtin_frame_address() calls.
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> > > --- > > arch/x86/include/asm/thread_info.h | 46 ++++++++------------------------------ > > arch/x86/lib/usercopy.c | 43 +++++++++++++++++++++++++++++++++++ > > 2 files changed, 52 insertions(+), 37 deletions(-) > > > > diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h > > index 8b7c8d8e..fd849e6 100644 > > --- a/arch/x86/include/asm/thread_info.h > > +++ b/arch/x86/include/asm/thread_info.h > > @@ -176,49 +176,21 @@ static inline unsigned long current_stack_pointer(void) > > return sp; > > } > > > > -/* > > - * Walks up the stack frames to make sure that the specified object is > > - * entirely contained by a single stack frame. > > - * > > - * Returns: > > - * 1 if within a frame > > - * -1 if placed across a frame boundary (or outside stack) > > - * 0 unable to determine (no frame pointers, etc) > > - */ > > +#ifdef CONFIG_HARDENED_USERCOPY > > This ifdef shouldn't be needed: the arch_within_stack_frames wasn't > designed to depend on it. > > > +#ifdef CONFIG_FRAME_POINTER > > +int arch_within_stack_frames(const void * const stack, > > + const void * const stackend, > > + const void *obj, unsigned long len); > > +#else > > static inline int arch_within_stack_frames(const void * const stack, > > const void * const stackend, > > const void *obj, unsigned long len) > > { > > -#if defined(CONFIG_FRAME_POINTER) > > - const void *frame = NULL; > > - const void *oldframe; > > - > > - oldframe = __builtin_frame_address(1); > > - if (oldframe) > > - frame = __builtin_frame_address(2); > > - /* > > - * low ----------------------------------------------> high > > - * [saved bp][saved ip][args][local vars][saved bp][saved ip] > > - * ^----------------^ > > - * allow copies only within here > > - */ > > - while (stack <= frame && frame < stackend) { > > - /* > > - * If obj + len extends past the last frame, this > > - * check won't pass and the next frame will be 0, > > - * causing us to bail out and correctly report > > - * the copy as invalid. > > - */ > > - if (obj + len <= frame) > > - return obj >= oldframe + 2 * sizeof(void *) ? 1 : -1; > > - oldframe = frame; > > - frame = *(const void * const *)frame; > > - } > > - return -1; > > -#else > > return 0; > > -#endif > > } > > +#endif /* CONFIG_FRAME_POINTER */ > > +#endif /* CONFIG_HARDENED_USERCOPY */ > > + > > > > #else /* !__ASSEMBLY__ */ > > > > diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c > > index b490878..96ce151 100644 > > --- a/arch/x86/lib/usercopy.c > > +++ b/arch/x86/lib/usercopy.c > > @@ -9,6 +9,7 @@ > > > > #include <asm/word-at-a-time.h> > > #include <linux/sched.h> > > +#include <asm/unwind.h> > > > > /* > > * We rely on the nested NMI work to allow atomic faults from the NMI path; the > > @@ -34,3 +35,45 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n) > > return ret; > > } > > EXPORT_SYMBOL_GPL(copy_from_user_nmi); > > + > > +#ifdef CONFIG_HARDENED_USERCOPY > > Same thing: no need to check CONFIG_HARDENED_USERCOPY here: it should > be checking CONFIG_FRAME_POINTER instead.
Now that this function is no longer inlined and is instead compiled in its own .c file, I was thinking that the tinyconfig folks would appreciate not growing the text size if there's no reason to do so. Keeping this #ifdef won't break anything, right?
Also I moved the CONFIG_FRAME_POINTER check to the header file so it doesn't pollute the .c code.
-- Josh
| |