On Fri, Feb 14, 2014 at 8:22 AM, Dave Martin <dave.mar...@arm.com> wrote: > On Thu, Feb 13, 2014 at 05:04:10PM -0800, Kees Cook wrote: >> Introduce "CONFIG_DEBUG_RODATA" to mostly match the x86 config, though >> the behavior is different: it depends on STRICT_KERNMEM_PERMS, which >> sets rodata read-only (but executable), where as this option additionally >> splits rodata from the kernel text (resulting in potentially more memory >> lost to padding) and sets it non-executable as well. The end result is >> that on builds with CONFIG_DEBUG_RODATA=y (like x86) the rodata with be >> marked purely read-only. > > This triggers an Oops in kexec, because we have a block of code in .text > which is a template for generating baremetal code to relocate the new > kernel, and some literal words are written into it before copying.
You're writing into the text area? I would imagine that CONFIG_ARM_KERNMEM_PERMS would break that. However, that's not the right place to be building code -- shouldn't the module area be used for that? > Possibly this should be in .rodata, not .text. Well, rodata should be neither writable nor executable. > There may be a few other instances of this kind of thing. This config will certainly find them! :) But, that's why it's behind a config. > Are you aware of similar situations on other arches? I think there were some problems a long time ago on x86 for rodata too. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
