diff mbox series

[v26,8/9] x86/vdso/32: Add ENDBR to __kernel_vsyscall entry point

Message ID 20210427204720.25007-9-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 April 27, 2021, 8:47 p.m. UTC 
From: "H.J. Lu" <hjl.tools@gmail.com>

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 that to __kernel_vsyscall entry point.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
---
 arch/x86/entry/vdso/vdso32/system_call.S | 2 ++
 1 file changed, 2 insertions(+)

Comments

Kees Cook April 28, 2021, 8:39 p.m. UTC | #1 
On Tue, Apr 27, 2021 at 01:47:19PM -0700, Yu-cheng Yu wrote:
> From: "H.J. Lu" <hjl.tools@gmail.com>
> 
> 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 that to __kernel_vsyscall entry point.
> 
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S
index de1fff7188aa..7793dc221726 100644
--- a/arch/x86/entry/vdso/vdso32/system_call.S
+++ b/arch/x86/entry/vdso/vdso32/system_call.S
@@ -7,6 +7,7 @@ 
 #include <asm/dwarf2.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative-asm.h>
+#include <asm/vdso.h>
 
 	.text
 	.globl __kernel_vsyscall
@@ -14,6 +15,7 @@ 
 	ALIGN
 __kernel_vsyscall:
 	CFI_STARTPROC
+	ENDBR32
 	/*
 	 * Reshuffle regs so that all of any of the entry instructions
 	 * will preserve enough state.