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 <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
---
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 99dafac992e2..c7cb85d57b3f 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
+ ENDBR64
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
+ ENDBR64
/* 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:
+ ENDBR64
mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
/* Set the exception info. */
--
2.21.0
On Fri, May 21, 2021 at 03:15:31PM -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 <[email protected]>
> Reviewed-by: Kees Cook <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Jarkko Sakkinen <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
Acked-by: Jarkko Sakkinen <[email protected]>
> ---
> 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 99dafac992e2..c7cb85d57b3f 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
> + ENDBR64
> 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
> + ENDBR64
>
> /* 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:
> + ENDBR64
> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
>
> /* Set the exception info. */
> --
> 2.21.0
>
>
/Jarkko
On 5/22/2021 3:47 PM, Jarkko Sakkinen wrote:
> On Fri, May 21, 2021 at 03:15:31PM -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 <[email protected]>
>> Reviewed-by: Kees Cook <[email protected]>
>> Cc: Andy Lutomirski <[email protected]>
>> Cc: Borislav Petkov <[email protected]>
>> Cc: Dave Hansen <[email protected]>
>> Cc: Jarkko Sakkinen <[email protected]>
>> Cc: Peter Zijlstra <[email protected]>
>
>
> Acked-by: Jarkko Sakkinen <[email protected]>
>
>> ---
>> 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 99dafac992e2..c7cb85d57b3f 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
>> + ENDBR64
>> 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
>> + ENDBR64
>>
>> /* 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:
>> + ENDBR64
>> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
>>
>> /* Set the exception info. */
>> --
>> 2.21.0
>>
>>
>
> /Jarkko
>
Thanks!