From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Russell Currey <ruscur@russell.cc>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powerpc/powernv/idle: Restore IAMR after idle
Date: Thu, 28 Feb 2019 15:24:10 +0530 [thread overview]
Message-ID: <20190228095410.GC24751@in.ibm.com> (raw)
In-Reply-To: <20190208111103.4901-1-ruscur@russell.cc>
Hello Russell,
On Fri, Feb 08, 2019 at 10:11:03PM +1100, Russell Currey wrote:
> Without restoring the IAMR after idle, execution prevention on POWER9
> with Radix MMU is overwritten and the kernel can freely execute userspace without
> faulting.
>
> This is necessary when returning from any stop state that modifies user
> state, as well as hypervisor state.
>
> To test how this fails without this patch, load the lkdtm driver and
> do the following:
>
> echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT
>
> which won't fault, then boot the kernel with powersave=off, where it
> will fault. Applying this patch will fix this.
>
> Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of user
> space")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> ---
> Since v1:
> - no longer use paca to save IAMR, instead use _DAR (thanks mpe)
Looks good to me. Once we move to Nick Piggin's C-based save/restore
code, we will be saving all these SPR values on the stack anyway.
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
--
Thanks and Regards
gautham.
prev parent reply other threads:[~2019-02-28 9:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-08 11:11 [PATCH v2] powerpc/powernv/idle: Restore IAMR after idle Russell Currey
2019-02-27 12:06 ` Akshay Adiga
2019-02-27 14:53 ` Nicholas Piggin
2019-02-28 9:54 ` Gautham R Shenoy [this message]
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