From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Michael Neuling <mikey@neuling.org>
Cc: Michael Neuling <mikey@neuling.org>,
Nicholas Piggin <npiggin@gmail.com>,
aneesh.kumar@linux.vnet.ibm.com, Breno Leitao <leitao@debian.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: powerpc/tm: Fix userspace r13 corruption
Date: Wed, 26 Sep 2018 22:13:10 +1000 (AEST) [thread overview]
Message-ID: <42KxfZ2RhHz9s4s@ozlabs.org> (raw)
In-Reply-To: <20180924072704.6200-1-mikey@neuling.org>
On Mon, 2018-09-24 at 07:27:04 UTC, Michael Neuling wrote:
> When we treclaim we store the userspace checkpointed r13 to a scratch
> SPR and then later save the scratch SPR to the user thread struct.
>
> Unfortunately, this doesn't work as accessing the user thread struct
> can take an SLB fault and the SLB fault handler will write the same
> scratch SPRG that now contains the userspace r13.
>
> To fix this, we store r13 to the kernel stack (which can't fault)
> before we access the user thread struct.
>
> Found by running P8 guest + powervm + disable_1tb_segments + TM. Seen
> as a random userspace segfault with r13 looking like a kernel address.
>
> Signed-off-by: Michael Neuling <mikey@neuling.org>
> Reviewed-by: Breno Leitao <leitao@debian.org>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/cf13435b730a502e814c63c84d93db
cheers
prev parent reply other threads:[~2018-09-26 12:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-24 7:27 [PATCH] powerpc/tm: Fix userspace r13 corruption Michael Neuling
2018-09-24 14:32 ` Breno Leitao
2018-09-25 5:24 ` Michael Neuling
2018-09-25 14:32 ` Breno Leitao
2018-09-26 12:13 ` Michael Ellerman [this message]
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