Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH 1/2] powerpc/pseries: block untrusted device tree changes when locked down | Date | Fri, 23 Sep 2022 17:03:59 +1000 |
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Paul Moore <paul@paul-moore.com> writes: > On Thu, Sep 22, 2022 at 3:38 PM Nathan Lynch <nathanl@linux.ibm.com> wrote: >> >> The /proc/powerpc/ofdt interface allows the root user to freely alter >> the in-kernel device tree, enabling arbitrary physical address writes >> via drivers that could bind to malicious device nodes, thus making it >> possible to disable lockdown. >> >> Historically this interface has been used on the pseries platform to >> facilitate the runtime addition and removal of processor, memory, and >> device resources (aka Dynamic Logical Partitioning or DLPAR). Years >> ago, the processor and memory use cases were migrated to designs that >> happen to be lockdown-friendly: device tree updates are communicated >> directly to the kernel from firmware without passing through untrusted >> user space. I/O device DLPAR via the "drmgr" command in powerpc-utils >> remains the sole legitimate user of /proc/powerpc/ofdt, but it is >> already broken in lockdown since it uses /dev/mem to allocate argument >> buffers for the rtas syscall. So only illegitimate uses of the >> interface should see a behavior change when running on a locked down >> kernel. >> >> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> >> --- >> arch/powerpc/platforms/pseries/reconfig.c | 5 +++++ >> include/linux/security.h | 1 + >> security/security.c | 1 + >> 3 files changed, 7 insertions(+) > > A couple of small nits below, but in general this seems reasonable. > However, as we are currently at -rc6 I would like us to wait to merge > this until after the upcoming merge window closes (I don't like > merging new functionality into -next at -rc6).
It's a bug fix, not a new feature IMHO.
I'd like to take it via the powerpc tree.
cheers
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