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Date:   Fri, 18 Oct 2019 13:04:29 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dave Martin <Dave.Martin@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        clang-built-linux@googlegroups.com,
        kernel-hardening@lists.openwall.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH 11/18] kprobes: disable kretprobes with SCS
Message-ID: <20191018130429.5df61f6b@gandalf.local.home>
In-Reply-To: <20191018161033.261971-12-samitolvanen@google.com>
References: <20191018161033.261971-1-samitolvanen@google.com>
        <20191018161033.261971-12-samitolvanen@google.com>
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[ Added Masami ]

On Fri, 18 Oct 2019 09:10:26 -0700
Sami Tolvanen <samitolvanen@google.com> wrote:

> With CONFIG_KRETPROBES, function return addresses are modified to
> redirect control flow to kretprobe_trampoline. This is incompatible with
> return address protection.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> ---
>  arch/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index a222adda8130..4646e3b34925 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -171,7 +171,7 @@ config ARCH_USE_BUILTIN_BSWAP
>  
>  config KRETPROBES
>  	def_bool y
> -	depends on KPROBES && HAVE_KRETPROBES
> +	depends on KPROBES && HAVE_KRETPROBES && ROP_PROTECTION_NONE

Again, this belongs in the arch code.

-- Steve

>  
>  config USER_RETURN_NOTIFIER
>  	bool


diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 41a9b4257b72..65557d7e6b5e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -166,7 +166,7 @@ config ARM64
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES
-	select HAVE_KRETPROBES
+	select HAVE_KRETPROBES if ROP_PROTECTION_NONE
 	select HAVE_GENERIC_VDSO
 	select IOMMU_DMA if IOMMU_SUPPORT
 	select IRQ_DOMAIN