[CRIU] [PATCH] arch/x86: Fix calculation of xstate_size

[Andrei Vagin]

Hi Cyrill and Dmitry,

Dima, could you review this patch?
Cyrill, could you create a pull-request on github?

Thanks,
Andrei

On Mon, May 18, 2020 at 1:19 AM Cyrill Gorcunov <gorcunov at gmail.com> wrote:
>
> The layout of xsave frame in a standart format is predefined by the hardware.
> Lets make sure we're increasing in frame offsets and use latest offset where
> appropriate.
>
> https://github.com/checkpoint-restore/criu/issues/1042
>
> Reported-by: Ashutosh Mehra <mehra.ashutosh at ibm.com>
> Signed-off-by: Cyrill Gorcunov <gorcunov at gmail.com>
> ---
>  criu/arch/x86/crtools.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/criu/arch/x86/crtools.c b/criu/arch/x86/crtools.c
> index 9c8beeedddf0..bc80225358ff 100644
> --- a/criu/arch/x86/crtools.c
> +++ b/criu/arch/x86/crtools.c
> @@ -437,6 +437,7 @@ int restore_fpu(struct rt_sigframe *sigframe, CoreEntry *core)
>                         void *from = xsave->member;                                     \
>                         size_t size = pb_repeated_size(xsave, member);                  \
>                         size_t xsize = (size_t)compel_fpu_feature_size(feature);        \
> +                       size_t xstate_size_next = off + xsize;                          \
>                         if (xsize != size) {                                            \
>                                 if (size) {                                             \
>                                         pr_err("%s reported %zu bytes (expecting %zu)\n",\
> @@ -448,7 +449,8 @@ int restore_fpu(struct rt_sigframe *sigframe, CoreEntry *core)
>                                 }                                                       \
>                         }                                                               \
>                         xstate_bv |= (1UL << feature);                                  \
> -                       xstate_size += xsize;                                           \
> +                       BUG_ON(xstate_size > xstate_size_next);                         \
> +                       xstate_size = xstate_size_next;                                 \
>                         memcpy(to, from, size);                                         \
>                 }                                                                       \
>         } while (0)
> @@ -485,6 +487,11 @@ int restore_fpu(struct rt_sigframe *sigframe, CoreEntry *core)
>                         UserX86XsaveEntry *xsave = core->thread_info->fpregs->xsave;
>                         uint8_t *extended_state_area = (void *)x;
>
> +                       /*
> +                        * Note the order does matter here and bound
> +                        * to the increasing offsets of XFEATURE_x
> +                        * inside memory layout (xstate_size calculation).
> +                        */
>                         assign_xsave(XFEATURE_YMM,      xsave, ymmh_space,      extended_state_area);
>                         assign_xsave(XFEATURE_BNDREGS,  xsave, bndreg_state,    extended_state_area);
>                         assign_xsave(XFEATURE_BNDCSR,   xsave, bndcsr_state,    extended_state_area);
> --
> 2.26.2
>