Re: PING^1: [PATCH] x86: Check corrupted return address when unwinding stack
On Wed, Oct 5, 2022 at 5:33 AM H.J. Lu wrote:
>
> On Wed, Sep 21, 2022 at 1:42 PM H.J. Lu wrote:
> >
> > If shadow stack is enabled, when unwinding stack, we count how many stack
> > frames we pop to reach the landing pad and adjust shadow stack by the same
> > amount. When counting the stack frame, we compare the return address on
> > normal stack against the return address on shadow stack. If they don't
> > match, return _URC_FATAL_PHASE2_ERROR for the corrupted return address on
> > normal stack. Don't check the return address for
> >
> > 1. Non-catchable exception where exception_class == 0. Process will be
> > terminated.
> > 2. Zero return address which marks the outermost stack frame.
> > 3. Signal stack frame since kernel puts a restore token on shadow stack.
Ok.
> >
> > * unwind-generic.h (_Unwind_Frames_Increment): Add the EXC
> > argument.
> > * unwind.inc (_Unwind_RaiseException_Phase2): Pass EXC to
> > _Unwind_Frames_Increment.
> > (_Unwind_ForcedUnwind_Phase2): Likewise.
> > * config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment):
> > Take the EXC argument. Return _URC_FATAL_PHASE2_ERROR if the
> > return address on normal stack doesn't match the return address
> > on shadow stack.
> > ---
> > libgcc/config/i386/shadow-stack-unwind.h | 51 ++--
> > libgcc/unwind-generic.h | 2 +-
> > libgcc/unwind.inc| 4 +-
> > 3 files changed, 50 insertions(+), 7 deletions(-)
> >
> > diff --git a/libgcc/config/i386/shadow-stack-unwind.h
> > b/libgcc/config/i386/shadow-stack-unwind.h
> > index 2b02682bdae..89d44165000 100644
> > --- a/libgcc/config/i386/shadow-stack-unwind.h
> > +++ b/libgcc/config/i386/shadow-stack-unwind.h
> > @@ -54,10 +54,39 @@ see the files COPYING3 and COPYING.RUNTIME
> > respectively. If not, see
> > aligned. If the original shadow stack is 8 byte aligned, we just
> > need to pop 2 slots, one restore token, from shadow stack. Otherwise,
> > we need to pop 3 slots, one restore token + 4 byte padding, from
> > - shadow stack. */
> > -#ifndef __x86_64__
> > + shadow stack.
> > +
> > + When popping a stack frame, we compare the return address on normal
> > + stack against the return address on shadow stack. If they don't match,
> > + return _URC_FATAL_PHASE2_ERROR for the corrupted return address on
> > + normal stack. Don't check the return address for
> > + 1. Non-catchable exception where exception_class == 0. Process will
> > + be terminated.
> > + 2. Zero return address which marks the outermost stack frame.
> > + 3. Signal stack frame since kernel puts a restore token on shadow
> > + stack.
> > + */
> > #undef _Unwind_Frames_Increment
> > -#define _Unwind_Frames_Increment(context, frames) \
> > +#ifdef __x86_64__
> > +#define _Unwind_Frames_Increment(exc, context, frames) \
> > +{ \
> > + frames++;\
> > + if (exc->exception_class != 0\
> > + && _Unwind_GetIP (context) != 0 \
> > + && !_Unwind_IsSignalFrame (context)) \
> > + { \
> > + _Unwind_Word ssp = _get_ssp (); \
> > + if (ssp != 0) \
> > + { \
> > + ssp += 8 * frames;\
> > + _Unwind_Word ra = *(_Unwind_Word *) ssp; \
> > + if (ra != _Unwind_GetIP (context))\
> > + return _URC_FATAL_PHASE2_ERROR; \
> > + } \
> > + } \
> > +}
> > +#else
> > +#define _Unwind_Frames_Increment(exc, context, frames) \
> >if (_Unwind_IsSignalFrame (context)) \
> > do \
> >{\
> > @@ -83,5 +112,19 @@ see the files COPYING3 and COPYING.RUNTIME
> > respectively. If not, see
> >}\
> > while (0); \
> >else \
> > -frames++;
> > +{ \
> > + frames++;\
> > + if (exc->exception_class != 0\
> > + && _Unwind_GetIP (context) != 0) \
> > + { \
> > + _Unwind_Word ssp = _get_ssp (); \
> > + if (ssp != 0) \
> > + { \
> > +
PING^1: [PATCH] x86: Check corrupted return address when unwinding stack
On Wed, Sep 21, 2022 at 1:42 PM H.J. Lu wrote:
>
> If shadow stack is enabled, when unwinding stack, we count how many stack
> frames we pop to reach the landing pad and adjust shadow stack by the same
> amount. When counting the stack frame, we compare the return address on
> normal stack against the return address on shadow stack. If they don't
> match, return _URC_FATAL_PHASE2_ERROR for the corrupted return address on
> normal stack. Don't check the return address for
>
> 1. Non-catchable exception where exception_class == 0. Process will be
> terminated.
> 2. Zero return address which marks the outermost stack frame.
> 3. Signal stack frame since kernel puts a restore token on shadow stack.
>
> * unwind-generic.h (_Unwind_Frames_Increment): Add the EXC
> argument.
> * unwind.inc (_Unwind_RaiseException_Phase2): Pass EXC to
> _Unwind_Frames_Increment.
> (_Unwind_ForcedUnwind_Phase2): Likewise.
> * config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment):
> Take the EXC argument. Return _URC_FATAL_PHASE2_ERROR if the
> return address on normal stack doesn't match the return address
> on shadow stack.
> ---
> libgcc/config/i386/shadow-stack-unwind.h | 51 ++--
> libgcc/unwind-generic.h | 2 +-
> libgcc/unwind.inc| 4 +-
> 3 files changed, 50 insertions(+), 7 deletions(-)
>
> diff --git a/libgcc/config/i386/shadow-stack-unwind.h
> b/libgcc/config/i386/shadow-stack-unwind.h
> index 2b02682bdae..89d44165000 100644
> --- a/libgcc/config/i386/shadow-stack-unwind.h
> +++ b/libgcc/config/i386/shadow-stack-unwind.h
> @@ -54,10 +54,39 @@ see the files COPYING3 and COPYING.RUNTIME respectively.
> If not, see
> aligned. If the original shadow stack is 8 byte aligned, we just
> need to pop 2 slots, one restore token, from shadow stack. Otherwise,
> we need to pop 3 slots, one restore token + 4 byte padding, from
> - shadow stack. */
> -#ifndef __x86_64__
> + shadow stack.
> +
> + When popping a stack frame, we compare the return address on normal
> + stack against the return address on shadow stack. If they don't match,
> + return _URC_FATAL_PHASE2_ERROR for the corrupted return address on
> + normal stack. Don't check the return address for
> + 1. Non-catchable exception where exception_class == 0. Process will
> + be terminated.
> + 2. Zero return address which marks the outermost stack frame.
> + 3. Signal stack frame since kernel puts a restore token on shadow
> + stack.
> + */
> #undef _Unwind_Frames_Increment
> -#define _Unwind_Frames_Increment(context, frames) \
> +#ifdef __x86_64__
> +#define _Unwind_Frames_Increment(exc, context, frames) \
> +{ \
> + frames++;\
> + if (exc->exception_class != 0\
> + && _Unwind_GetIP (context) != 0 \
> + && !_Unwind_IsSignalFrame (context)) \
> + { \
> + _Unwind_Word ssp = _get_ssp (); \
> + if (ssp != 0) \
> + { \
> + ssp += 8 * frames;\
> + _Unwind_Word ra = *(_Unwind_Word *) ssp; \
> + if (ra != _Unwind_GetIP (context))\
> + return _URC_FATAL_PHASE2_ERROR; \
> + } \
> + } \
> +}
> +#else
> +#define _Unwind_Frames_Increment(exc, context, frames) \
>if (_Unwind_IsSignalFrame (context)) \
> do \
>{\
> @@ -83,5 +112,19 @@ see the files COPYING3 and COPYING.RUNTIME respectively.
> If not, see
>}\
> while (0); \
>else \
> -frames++;
> +{ \
> + frames++;\
> + if (exc->exception_class != 0\
> + && _Unwind_GetIP (context) != 0) \
> + { \
> + _Unwind_Word ssp = _get_ssp (); \
> + if (ssp != 0) \
> + { \
> + ssp += 4 * frames;\
> + _Unwind_Word ra = *(_Unwind_Word *) ssp; \
> + if (ra != _Unwind_GetIP (context))\
> + return _URC_FATAL_PHASE2_ERROR; \
> +
