diff mbox series

[v27,10/10] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave

Message ID 20210521221531.30168-11-yu-cheng.yu@intel.com (mailing list archive)
State New, archived
Headers show
Series Control-flow Enforcement: Indirect Branch Tracking | expand

Commit Message

Yu-cheng Yu May 21, 2021, 10:15 p.m. UTC 
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>
Reviewed-by: Kees Cook <keescook@chromium.org>
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>
---
 arch/x86/entry/vdso/vsgx.S | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Jarkko Sakkinen May 22, 2021, 10:47 p.m. UTC | #1 
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 <yu-cheng.yu@intel.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 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 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
Yu-cheng Yu May 24, 2021, 7:01 p.m. UTC | #2 
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 <yu-cheng.yu@intel.com>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> 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 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!
diff mbox series

Patch

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. */