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Tue, 23 Jun 2020 11:46:40 -0700 (PDT) Subject: Re: [PATCH stable 4.9] arm64: entry: Place an SB sequence following an ERET instruction To: linux-arm-kernel@lists.infradead.org, will@kernel.org, Catalin Marinas Cc: stable@vger.kernel.org, Will Deacon , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Christoffer Dall , Marc Zyngier , open list , "open list:KERNEL VIRTUAL MACHINE (KVM)" , "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" References: <20200612044219.31606-1-f.fainelli@gmail.com> From: Florian Fainelli Autocrypt: addr=f.fainelli@gmail.com; prefer-encrypt=mutual; keydata= xsDiBEjPuBIRBACW9MxSJU9fvEOCTnRNqG/13rAGsj+vJqontvoDSNxRgmafP8d3nesnqPyR xGlkaOSDuu09rxuW+69Y2f1TzjFuGpBk4ysWOR85O2Nx8AJ6fYGCoeTbovrNlGT1M9obSFGQ X3IzRnWoqlfudjTO5TKoqkbOgpYqIo5n1QbEjCCwCwCg3DOH/4ug2AUUlcIT9/l3pGvoRJ0E AICDzi3l7pmC5IWn2n1mvP5247urtHFs/uusE827DDj3K8Upn2vYiOFMBhGsxAk6YKV6IP0d ZdWX6fqkJJlu9cSDvWtO1hXeHIfQIE/xcqvlRH783KrihLcsmnBqOiS6rJDO2x1eAgC8meAX SAgsrBhcgGl2Rl5gh/jkeA5ykwbxA/9u1eEuL70Qzt5APJmqVXR+kWvrqdBVPoUNy/tQ8mYc nzJJ63ng3tHhnwHXZOu8hL4nqwlYHRa9eeglXYhBqja4ZvIvCEqSmEukfivk+DlIgVoOAJbh qIWgvr3SIEuR6ayY3f5j0f2ejUMYlYYnKdiHXFlF9uXm1ELrb0YX4GMHz80nRmxvcmlhbiBG YWluZWxsaSA8Zi5mYWluZWxsaUBnbWFpbC5jb20+wmYEExECACYCGyMGCwkIBwMCBBUCCAME FgIDAQIeAQIXgAUCVF/S8QUJHlwd3wAKCRBhV5kVtWN2DvCVAJ4u4/bPF4P3jxb4qEY8I2gS 6hG0gACffNWlqJ2T4wSSn+3o7CCZNd7SLSDOwU0EVxvH8AEQAOqv6agYuT4x3DgFIJNv9i0e S443rCudGwmg+CbjXGA4RUe1bNdPHYgbbIaN8PFkXfb4jqg64SyU66FXJJJO+DmPK/t7dRNA 3eMB1h0GbAHlLzsAzD0DKk1ARbjIusnc02aRQNsAUfceqH5fAMfs2hgXBa0ZUJ4bLly5zNbr r0t/fqZsyI2rGQT9h1D5OYn4oF3KXpSpo+orJD93PEDeseho1EpmMfsVH7PxjVUlNVzmZ+tc IDw24CDSXf0xxnaojoicQi7kzKpUrJodfhNXUnX2JAm/d0f9GR7zClpQMezJ2hYAX7BvBajb Wbtzwi34s8lWGI121VjtQNt64mSqsK0iQAE6OYk0uuQbmMaxbBTT63+04rTPBO+gRAWZNDmQ b2cTLjrOmdaiPGClSlKx1RhatzW7j1gnUbpfUl91Xzrp6/Rr9BgAZydBE/iu57KWsdMaqu84 JzO9UBGomh9eyBWBkrBt+Fe1qN78kM7JO6i3/QI56NA4SflV+N4PPgI8TjDVaxgrfUTV0gVa cr9gDE5VgnSeSiOleChM1jOByZu0JTShOkT6AcSVW0kCz3fUrd4e5sS3J3uJezSvXjYDZ53k +0GS/Hy//7PSvDbNVretLkDWL24Sgxu/v8i3JiYIxe+F5Br8QpkwNa1tm7FK4jOd95xvYADl BUI1EZMCPI7zABEBAAHCwagEGBECAAkFAlcbx/ACGwICKQkQYVeZFbVjdg7BXSAEGQECAAYF Alcbx/AACgkQh9CWnEQHBwSJBw//Z5n6IO19mVzMy/ZLU/vu8flv0Aa0kwk5qvDyvuvfiDTd WQzq2PLs+obX0y1ffntluhvP+8yLzg7h5O6/skOfOV26ZYD9FeV3PIgR3QYF26p2Ocwa3B/k P6ENkk2pRL2hh6jaA1Bsi0P34iqC2UzzLq+exctXPa07ioknTIJ09BT31lQ36Udg7NIKalnj 5UbkRjqApZ+Rp0RAP9jFtq1n/gjvZGyEfuuo/G+EVCaiCt3Vp/cWxDYf2qsX6JxkwmUNswuL C3duQ0AOMNYrT6Pn+Vf0kMboZ5UJEzgnSe2/5m8v6TUc9ZbC5I517niyC4+4DY8E2m2V2LS9 es9uKpA0yNcd4PfEf8bp29/30MEfBWOf80b1yaubrP5y7yLzplcGRZMF3PgBfi0iGo6kM/V2 13iD/wQ45QTV0WTXaHVbklOdRDXDHIpT69hFJ6hAKnnM7AhqZ70Qi31UHkma9i/TeLLzYYXz zhLHGIYaR04dFT8sSKTwTSqvm8rmDzMpN54/NeDSoSJitDuIE8givW/oGQFb0HGAF70qLgp0 2XiUazRyRU4E4LuhNHGsUxoHOc80B3l+u3jM6xqJht2ZyMZndbAG4LyVA2g9hq2JbpX8BlsF skzW1kbzIoIVXT5EhelxYEGqLFsZFdDhCy8tjePOWK069lKuuFSssaZ3C4edHtkZ8gCfWWtA 8dMsqeOIg9Trx7ZBCDOZGNAAnjYQmSb2eYOAti3PX3Ex7vI8ZhJCzsNNBEjPuBIQEAC/6NPW 6EfQ91ZNU7e/oKWK91kOoYGFTjfdOatp3RKANidHUMSTUcN7J2mxww80AQHKjr3Yu2InXwVX SotMMR4UrkQX7jqabqXV5G+88bj0Lkr3gi6qmVkUPgnNkIBe0gaoM523ujYKLreal2OQ3GoJ PS6hTRoSUM1BhwLCLIWqdX9AdT6FMlDXhCJ1ffA/F3f3nTN5oTvZ0aVF0SvQb7eIhGVFxrlb WS0+dpyulr9hGdU4kzoqmZX9T/r8WCwcfXipmmz3Zt8o2pYWPMq9Utby9IEgPwultaP06MHY nhda1jfzGB5ZKco/XEaXNvNYADtAD91dRtNGMwRHWMotIGiWwhEJ6vFc9bw1xcR88oYBs+7p gbFSpmMGYAPA66wdDKGj9+cLhkd0SXGht9AJyaRA5AWB85yNmqcXXLkzzh2chIpSEawRsw8B rQIZXc5QaAcBN2dzGN9UzqQArtWaTTjMrGesYhN+aVpMHNCmJuISQORhX5lkjeg54oplt6Zn QyIsOCH3MfG95ha0TgWwyFtdxOdY/UY2zv5wGivZ3WeS0TtQf/BcGre2y85rAohFziWOzTaS BKZKDaBFHwnGcJi61Pnjkz82hena8OmsnsBIucsz4N0wE+hVd6AbDYN8ZcFNIDyt7+oGD1+c PfqLz2df6qjXzq27BBUboklbGUObNwADBQ//V45Z51Q4fRl/6/+oY5q+FPbRLDPlUF2lV6mb hymkpqIzi1Aj/2FUKOyImGjbLAkuBQj3uMqy+BSSXyQLG3sg8pDDe8AJwXDpG2fQTyTzQm6l OnaMCzosvALk2EOPJryMkOCI52+hk67cSFA0HjgTbkAv4Mssd52y/5VZR28a+LW+mJIZDurI Y14UIe50G99xYxjuD1lNdTa/Yv6qFfEAqNdjEBKNuOEUQOlTLndOsvxOOPa1mRUk8Bqm9BUt LHk3GDb8bfDwdos1/h2QPEi+eI+O/bm8YX7qE7uZ13bRWBY+S4+cd+Cyj8ezKYAJo9B+0g4a RVhdhc3AtW44lvZo1h2iml9twMLfewKkGV3oG35CcF9mOd7n6vDad3teeNpYd/5qYhkopQrG k2oRBqxyvpSLrJepsyaIpfrt5NNaH7yTCtGXcxlGf2jzGdei6H4xQPjDcVq2Ra5GJohnb/ix uOc0pWciL80ohtpSspLlWoPiIowiKJu/D/Y0bQdatUOZcGadkywCZc/dg5hcAYNYchc8AwA4 2dp6w8SlIsm1yIGafWlNnfvqbRBglSTnxFuKqVggiz2zk+1wa/oP+B96lm7N4/3Aw6uy7lWC HvsHIcv4lxCWkFXkwsuWqzEKK6kxVpRDoEQPDj+Oy/ZJ5fYuMbkdHrlegwoQ64LrqdmiVVPC TwQYEQIADwIbDAUCVF/S8QUJHlwd3wAKCRBhV5kVtWN2Do+FAJ956xSz2XpDHql+Wg/2qv3b G10n8gCguORqNGMsVRxrlLs7/himep7MrCc= Message-ID: <2bcebe48-1218-403a-798c-da30d678fdd6@gmail.com> Date: Tue, 23 Jun 2020 11:46:37 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200612044219.31606-1-f.fainelli@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/11/20 9:42 PM, Florian Fainelli wrote: > From: Will Deacon > > commit 679db70801da9fda91d26caf13bf5b5ccc74e8e8 upstream > > Some CPUs can speculate past an ERET instruction and potentially perform > speculative accesses to memory before processing the exception return. > Since the register state is often controlled by a lower privilege level > at the point of an ERET, this could potentially be used as part of a > side-channel attack. > > This patch emits an SB sequence after each ERET so that speculation is > held up on exception return. > > Signed-off-by: Will Deacon > [florian: Adjust hyp-entry.S to account for the label] > Signed-off-by: Florian Fainelli > --- > Will, > > Can you confirm that for 4.9 these are the only places that require > patching? Thank you! Hi Will, Catalin, Does this look good to you for a 4.9 backport? I would like to see this included at some point since this pertains to CVE-2020-13844. Thanks! -- Florian