lkml.org 
[lkml]   [2020]   [Feb]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC PATCH v9 24/27] x86/cet/shstk: ELF header parsing for Shadow Stack
    On Wed, Feb 05, 2020 at 10:19:32AM -0800, Yu-cheng Yu wrote:
    > Check an ELF file's .note.gnu.property, and setup Shadow Stack if the
    > application supports it.
    >
    > v9:
    > - Change cpu_feature_enabled() to static_cpu_has().
    >
    > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
    > ---
    > arch/x86/Kconfig | 2 ++
    > arch/x86/include/asm/elf.h | 13 +++++++++++++
    > arch/x86/kernel/process_64.c | 31 +++++++++++++++++++++++++++++++
    > 3 files changed, 46 insertions(+)
    >
    > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    > index 6c34b701c588..d1447380e02e 100644
    > --- a/arch/x86/Kconfig
    > +++ b/arch/x86/Kconfig
    > @@ -1987,6 +1987,8 @@ config X86_INTEL_SHADOW_STACK_USER
    > select ARCH_USES_HIGH_VMA_FLAGS
    > select X86_INTEL_CET
    > select ARCH_HAS_SHSTK
    > + select ARCH_USE_GNU_PROPERTY
    > + select ARCH_BINFMT_ELF_STATE
    > ---help---
    > Shadow Stack (SHSTK) provides protection against program
    > stack corruption. It is active when the kernel has this
    > diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
    > index 69c0f892e310..fac79b621e0a 100644
    > --- a/arch/x86/include/asm/elf.h
    > +++ b/arch/x86/include/asm/elf.h
    > @@ -367,6 +367,19 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
    > int uses_interp);
    > #define compat_arch_setup_additional_pages compat_arch_setup_additional_pages
    >
    > +#ifdef CONFIG_ARCH_BINFMT_ELF_STATE
    > +struct arch_elf_state {
    > + unsigned int gnu_property;
    > +};
    > +
    > +#define INIT_ARCH_ELF_STATE { \
    > + .gnu_property = 0, \
    > +}
    > +
    > +#define arch_elf_pt_proc(ehdr, phdr, elf, interp, state) (0)
    > +#define arch_check_elf(ehdr, interp, interp_ehdr, state) (0)
    > +#endif
    > +
    > /* Do not change the values. See get_align_mask() */
    > enum align_flags {
    > ALIGN_VA_32 = BIT(0),
    > diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
    > index 506d66830d4d..99548cde0cc6 100644
    > --- a/arch/x86/kernel/process_64.c
    > +++ b/arch/x86/kernel/process_64.c
    > @@ -732,3 +732,34 @@ unsigned long KSTK_ESP(struct task_struct *task)
    > {
    > return task_pt_regs(task)->sp;
    > }
    > +
    > +#ifdef CONFIG_ARCH_USE_GNU_PROPERTY
    > +int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
    > + bool compat, struct arch_elf_state *state)
    > +{
    > + if (type != GNU_PROPERTY_X86_FEATURE_1_AND)
    > + return 0;
    > +
    > + if (datasz != sizeof(unsigned int))
    > + return -ENOEXEC;
    > +
    > + state->gnu_property = *(unsigned int *)data;
    > + return 0;
    > +}
    > +
    > +int arch_setup_elf_property(struct arch_elf_state *state)
    > +{
    > + int r = 0;
    > +
    > + memset(&current->thread.cet, 0, sizeof(struct cet_status));
    > +
    > + if (static_cpu_has(X86_FEATURE_SHSTK)) {
    > + if (state->gnu_property & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
    > + r = cet_setup_shstk();
    > + if (r < 0)
    > + return r;

    This test is redundant; there's no loop. This can just fall through to
    the final return.

    -Kees

    > + }
    > +
    > + return r;
    > +}
    > +#endif
    > --
    > 2.21.0
    >

    --
    Kees Cook

    \
     
     \ /
      Last update: 2020-02-25 22:23    [W:7.345 / U:0.100 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site