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SubjectRe: [PATCH v24 9/9] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave
On Thu, Apr 01, 2021 at 03:14:03PM -0700, Yu-cheng Yu wrote:
> ENDBR is a special new instruction for the Indirect Branch Tracking (IBT)
> component of CET. IBT prevents attacks by ensuring that (most) indirect
> branches and function calls may only land at ENDBR instructions. Branches
> that don't follow the rules will result in control flow (#CF) exceptions.
>
> ENDBR is a noop when IBT is unsupported or disabled. Most ENDBR
> instructions are inserted automatically by the compiler, but branch
> targets written in assembly must have ENDBR added manually.
>
> Add ENDBR to __vdso_sgx_enter_enclave() branch targets.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Jarkko Sakkinen <jarkko@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>

Acked-by: Jarkko Sakkinen <jarkko@kernel.org>

> ---
> arch/x86/entry/vdso/vsgx.S | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/entry/vdso/vsgx.S b/arch/x86/entry/vdso/vsgx.S
> index 86a0e94f68df..c63eafa54abd 100644
> --- a/arch/x86/entry/vdso/vsgx.S
> +++ b/arch/x86/entry/vdso/vsgx.S
> @@ -4,6 +4,7 @@
> #include <asm/export.h>
> #include <asm/errno.h>
> #include <asm/enclu.h>
> +#include <asm/vdso.h>
>
> #include "extable.h"
>
> @@ -27,6 +28,7 @@
> SYM_FUNC_START(__vdso_sgx_enter_enclave)
> /* Prolog */
> .cfi_startproc
> + ENDBR
> push %rbp
> .cfi_adjust_cfa_offset 8
> .cfi_rel_offset %rbp, 0
> @@ -62,6 +64,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
> .Lasync_exit_pointer:
> .Lenclu_eenter_eresume:
> enclu
> + ENDBR
>
> /* EEXIT jumps here unless the enclave is doing something fancy. */
> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
> @@ -91,6 +94,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
> jmp .Lout
>
> .Lhandle_exception:
> + ENDBR
> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
>
> /* Set the exception info. */
> --
> 2.21.0
>
>

/Jarkko

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