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To: Nathan Fontenot <nfont@linux.vnet.ibm.com>,
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From: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: powerpc/pseries: Verify CPU doesn't exist before adding
Message-Id: <20151217115736.882F7140317@ozlabs.org>
Date: Thu, 17 Dec 2015 22:57:36 +1100 (AEDT)
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On Fri, 2015-23-10 at 17:45:57 UTC, Nathan Fontenot wrote:
> When DLPAR adding a CPU we should verify that the CPU does not already
> exist. Failure to do so can generate a kernel oops;
> 
> [    9.465585] kernel BUG at arch/powerpc/platforms/pseries/dlpar.c:382!
> [    9.465796] Oops: Exception in kernel mode, sig: 5 [#1]
> 
> This oops can be generated by causing a probe to be performed on a cpu
> by writing to the sysfs cpu probe file (/sys/devices/system/cpu/probe).
> This patch adds a check for the existence of cpu prior to probing the cpu
> so userspace doing the wrong thing won't trigger a BUG_ON().
> 
> Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/1f859adb9253c2010799625822

cheers