linux-kernel - Re: [PATCH] powerpc/Kconfig: Force THREAD

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87h756kz0s.fsf@mpe.ellerman.id.au>
Date:   Tue, 31 May 2022 16:16:19 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Erhard Furtner <erhard_f@...lbox.org>
Subject: Re: [PATCH] powerpc/Kconfig: Force THREAD_SHIFT to at least 14 with
 KASAN

Christophe Leroy <christophe.leroy@...roup.eu> writes:
> Allthough 14 is the default THREAD_SHIFT when KASAN is selected,
> taking an old config may keep 13 when CONFIG_EXPERT is selected.
>
> Force it to 14 as a minimum when KASAN is selected.
>
> Also default to 15 when KASAN on PPC64.
>
> Reported-by: Erhard Furtner <erhard_f@...lbox.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/Kconfig | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

I was thinking of doing it in C, similar to the way arm64 handles it.

Something like below. It means we always double the stack size when
KASAN is enabled. I think it's preferable, as it will always work
regardless of whether the user has an old .config (or is bisectting)?

cheers

diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 125328d1b980..c9735f93f8e6 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -14,12 +14,17 @@
 
 #ifdef __KERNEL__
 
-#if defined(CONFIG_VMAP_STACK) && CONFIG_THREAD_SHIFT < PAGE_SHIFT
-#define THREAD_SHIFT		PAGE_SHIFT
+#ifdef CONFIG_KASAN
+#define THREAD_SHIFT		(CONFIG_THREAD_SHIFT + 1)
 #else
 #define THREAD_SHIFT		CONFIG_THREAD_SHIFT
 #endif
 
+#if defined(CONFIG_VMAP_STACK) && THREAD_SHIFT < PAGE_SHIFT
+#undef THREAD_SHIFT
+#define THREAD_SHIFT		PAGE_SHIFT
+#endif
+
 #define THREAD_SIZE		(1 << THREAD_SHIFT)
 
 /*