Re: [RFC PATCH v2 20/21] x86: Add support for CONFIG_CFI_CLANG
From: Kees Cook <hidden>
Date: 2022-05-15 03:20:03
Also in:
linux-hardening, lkml, llvm
On Fri, May 13, 2022 at 01:21:58PM -0700, Sami Tolvanen wrote:
With CONFIG_CFI_CLANG, the compiler injects a type preamble
immediately before each function and a check to validate the target
function type before indirect calls:
; type preamble
__cfi_function:
int3
int3
mov <id>, %eax
int3
int3
function:
...
; indirect call check
cmpl <id>, -6(%r11)
je .Ltmp1
ud2
.Ltmp1:
call __x86_indirect_thunk_r11
Define the __CFI_TYPE helper macro for manual type annotations in
assembly code, add error handling for the CFI ud2 traps, and allow
CONFIG_CFI_CLANG to be selected on x86_64.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>Looks good testing with LKDTM... $ echo CFI_FORWARD_PROTO | cat >/sys/kernel/debug/provoke-crash/DIRECT [ 144.084017] lkdtm: Performing direct entry CFI_FORWARD_PROTO [ 144.086138] lkdtm: Calling matched prototype ... [ 144.087833] lkdtm: Calling mismatched prototype ... [ 144.089777] CFI failure at lkdtm_CFI_FORWARD_PROTO+0x34/0x67 [lkdtm] (target: lkdtm_increment_int+0x0/0x7 [lkdtm]; expected type: 0x7e0c52a5) Tested-by: Kees Cook <redacted> -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel