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Message-ID: <20170905212742.GG5024@atomide.com>
Date: Tue, 5 Sep 2017 14:27:42 -0700
From: Tony Lindgren <tony@...mide.com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Arnd Bergmann <arnd@...db.de>, Nicolas Pitre <nico@...aro.org>,
Russell King <linux@...linux.org.uk>,
Kees Cook <keescook@...omium.org>,
Thomas Garnier <thgarnie@...gle.com>,
Marc Zyngier <marc.zyngier@....com>,
Mark Rutland <mark.rutland@....com>,
Matt Fleming <matt@...eblueprint.co.uk>,
Dave Martin <dave.martin@....com>
Subject: Re: [PATCH v2 00/29] implement KASLR for ARM
* Ard Biesheuvel <ard.biesheuvel@...aro.org> [170905 12:43]:
> Right. Well, I will try to reproduce with the BB white I have.
Yeah that should be reproducable, I got it to happen on BBB here
after about 5 boots.
> Are you booting with an initrd?
Not on this one, on beagleboard xm I do.
> >> > Then loading modules with CONFIG_RANDOMIZE_BASE=y seems to fail with:
> >> >
> >> > $ sudo modprobe rtc-twl
> >> > rtc_twl: disagrees about version of symbol module_layout
> >> > modprobe: ERROR: could not insert 'rtc_twl': Exec format error
> >> >
> >>
> >> Is this with CONFIG_MODVERSIONS enabled?
> >
> > Yes, but disabling that did not seem to make any difference
> > based on just one test.
> >
>
> Yeah, well, it appears I missed a couple of details :-)
>
> This should fix the module loading issues:
Yeah now modprobe works :) That's after manually applying
it as the tabs got munched in your patch somewhere, see below.
Regards,
Tony
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 1a0304dd388d..bbefd5f32ec2 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1830,6 +1830,8 @@ config RANDOMIZE_BASE
> depends on MMU && AUTO_ZRELADDR
> depends on !XIP_KERNEL && !ZBOOT_ROM
> select RELOCATABLE
> + select ARM_MODULE_PLTS if MODULES
> + select MODULE_REL_CRCS if MODVERSIONS
> help
> Randomizes the virtual and physical address at which the kernel
> image is loaded, as a security feature that deters exploit attempts
> diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
> index f13ae153fb24..b56fc4dd27b6 100644
> --- a/arch/arm/include/asm/elf.h
> +++ b/arch/arm/include/asm/elf.h
> @@ -50,6 +50,7 @@ typedef struct user_fp elf_fpregset_t;
> #define R_ARM_NONE 0
> #define R_ARM_PC24 1
> #define R_ARM_ABS32 2
> +#define R_ARM_REL32 3
> #define R_ARM_CALL 28
> #define R_ARM_JUMP24 29
> #define R_ARM_TARGET1 38
> diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
> index 3ff571c2c71c..aa4d72837cd5 100644
> --- a/arch/arm/kernel/module.c
> +++ b/arch/arm/kernel/module.c
> @@ -175,6 +175,10 @@
> *(u32 *)loc |= offset & 0x7fffffff;
> break;
>
> + case R_ARM_REL32:
> + *(u32 *)loc += sym->st_value - loc;
> + break;
> +
> case R_ARM_MOVW_ABS_NC:
> case R_ARM_MOVT_ABS:
> offset = tmp = __mem_to_opcode_arm(*(u32 *)loc);
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