Messages in this thread | | | From | "PaX Team" <> | Date | Wed, 25 Nov 2015 12:05:25 +0100 | Subject | Re: [kernel-hardening] [PATCH 0/2] introduce post-init read-only memory |
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On 25 Nov 2015 at 10:13, Mathias Krause wrote:
> I myself had some educating experience seeing my machine triple fault > when resuming from a S3 sleep. The root cause was a variable that was > annotated __read_only but that was (unnecessarily) modified during CPU > bring-up phase. Debugging that kind of problems is sort of a PITA, you > could imagine.
actually the kernel could silently recover from this given how the page fault handler could easily determine that the fault address fell into the data..read_only section and just silently undo the read-only property, log the event to dmesg and retry the faulting access.
> So, prior extending the usage of the __read_only annotation some > toolchain support is needed. Maybe a gcc plugin that'll warn/error on > code that writes to such a variable but is not __init itself.
this is exactly what i suggested earlier in the constify thread ;). note that this will produce false positives because __init* annotations are not propagated everywhere they could be.
> The initify and checker plugins from the PaX patch might be worth to > look at for that purpose, as they're doing similar things already.
one of our plans for initify is to add the discovery and propagation of _init* annotations as well, it'd not only fix the false positives mentioned above but also help reduce the kernel size (code/data/rodata).
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