Date: Tue, 27 Aug 2019 23:05:30 -0500 From: Scott Wood <oss@...error.net> To: Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com, christophe.leroy@....fr, benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com, keescook@...omium.org, kernel-hardening@...ts.openwall.com Cc: wangkefeng.wang@...wei.com, linux-kernel@...r.kernel.org, jingxiangfeng@...wei.com, zhaohongjiang@...wei.com, thunder.leizhen@...wei.com, fanchengyang@...wei.com, yebin10@...wei.com Subject: Re: [PATCH v6 00/12] implement KASLR for powerpc/fsl_booke/32 On Fri, 2019-08-09 at 18:07 +0800, Jason Yan wrote: > This series implements KASLR for powerpc/fsl_booke/32, as a security > feature that deters exploit attempts relying on knowledge of the location > of kernel internals. > > Since CONFIG_RELOCATABLE has already supported, what we need to do is > map or copy kernel to a proper place and relocate. Have you tested this with a kernel that was loaded at a non-zero address? I tried loading a kernel at 0x04000000 (by changing the address in the uImage, and setting bootm_low to 04000000 in U-Boot), and it works without CONFIG_RANDOMIZE and fails with. > Freescale Book-E > parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1 > entries are not suitable to map the kernel directly in a randomized > region, so we chose to copy the kernel to a proper place and restart to > relocate. > > Entropy is derived from the banner and timer base, which will change every > build and boot. This not so much safe so additionally the bootloader may > pass entropy via the /chosen/kaslr-seed node in device tree. How complicated would it be to directly access the HW RNG (if present) that early in the boot? It'd be nice if a U-Boot update weren't required (and particularly concerning that KASLR would appear to work without a U-Boot update, but without decent entropy). -Scott
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