From: Dave Hansen <dave.hansen@intel.com>
To: Jarkko Sakkinen <jarkko@kernel.org>,
Dmitrii Kuvaiskii <dmitrii.kuvaiskii@intel.com>,
dave.hansen@linux.intel.com, kai.huang@intel.com,
haitao.huang@linux.intel.com, reinette.chatre@intel.com,
linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: mona.vij@intel.com, kailun.qin@intel.com, stable@vger.kernel.org,
"Marcelina Kościelnicka" <mwk@invisiblethingslab.com>
Subject: Re: [PATCH v2 1/2] x86/sgx: Resolve EAUG race where losing thread returns SIGBUS
Date: Wed, 15 May 2024 07:15:42 -0700 [thread overview]
Message-ID: <58e9d453-7909-4157-86fd-a2d5561e728e@intel.com> (raw)
In-Reply-To: <D1A9PC6LWL2S.38KB2X3EL9X79@kernel.org>
On 5/15/24 06:54, Jarkko Sakkinen wrote:
> I'd cut out 90% of the description out and just make the argument of
> the wrong error code, and done. The sequence is great for showing
> how this could happen. The prose makes my head hurt tbh.
The changelog is too long, but not fatally so. I'd much rather have a
super verbose description than something super sparse.
Would something like this make more sense to folks?
Imagine an mmap()'d file. Two threads touch the same address at
the same time and fault. Both allocate a physical page and race
to install a PTE for that page. Only one will win the race. The
loser frees its page, but still continues handling the fault as
a success and returns VM_FAULT_NOPAGE from the fault handler.
The same race can happen with SGX. But there's a bug: the loser
in the SGX steers into a failure path. The loser EREMOVE's the
winner's EPC page, then returns SIGBUS, likely killing the app.
Fix the SGX loser's behavior. Change the return code to
VM_FAULT_NOPAGE to avoid SIGBUS and call sgx_free_epc_page()
which avoids EREMOVE'ing the winner's page and only frees the
page that the loser allocated.
next prev parent reply other threads:[~2024-05-15 14:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-15 13:12 [PATCH v2 0/2] x86/sgx: Fix two data races in EAUG/EREMOVE flows Dmitrii Kuvaiskii
2024-05-15 13:12 ` [PATCH v2 1/2] x86/sgx: Resolve EAUG race where losing thread returns SIGBUS Dmitrii Kuvaiskii
2024-05-15 13:54 ` Jarkko Sakkinen
2024-05-15 13:56 ` Jarkko Sakkinen
2024-05-15 14:15 ` Dave Hansen [this message]
2024-05-15 14:28 ` Jarkko Sakkinen
2024-05-15 15:58 ` Reinette Chatre
2024-05-15 16:39 ` Jarkko Sakkinen
2024-05-15 22:01 ` Haitao Huang
2024-05-15 13:12 ` [PATCH v2 2/2] x86/sgx: Resolve EREMOVE page vs EAUG page data race Dmitrii Kuvaiskii
2024-05-15 14:44 ` Jarkko Sakkinen
2024-05-15 15:52 ` Reinette Chatre
2024-05-15 21:59 ` Haitao Huang
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