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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b2-20020a631b42000000b004cd1e132865sm5244496pgm.84.2023.01.19.17.06.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Jan 2023 17:06:53 -0800 (PST) Date: Thu, 19 Jan 2023 17:06:52 -0800 From: Kees Cook To: Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com Subject: Re: [PATCH v5 32/39] x86/shstk: Support WRSS for userspace Message-ID: <202301191706.BF1B7E3B0@keescook> References: <20230119212317.8324-1-rick.p.edgecombe@intel.com> <20230119212317.8324-33-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230119212317.8324-33-rick.p.edgecombe@intel.com> X-Stat-Signature: c8dq5homeabw936u78be3hqp3bxeyn97 X-Rspam-User: X-Rspamd-Queue-Id: 13D5A80012 X-Rspamd-Server: rspam06 X-HE-Tag: 1674176814-229254 X-HE-Meta: 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 No0lvawJ /FdD9HuTa4Na6I0AGo9SerwJstan0FHeKDLAbkbYvrsGhGDBzNI1Tppe0pqP1CTkQSBU+K42wTDFNZWNisxZ/8hy7wN3diktlA78/0CLT2A1DqO8QQ3uZ/cUsZaDK8RSH39iW8yKgqR/RVuEu7Ohq2OLyVE+AbGYPbrGFLQTTaCnn5JXSaJcrEkB1xenYxnLc2rtVtSyP89HlzckWjMbnB137N+ycuAfP19HnmAkwK7W4K2ieG29ncpichPPHnp8ur46xebxAHUm9A5JXDvXpJYibSzFj3Ts4phvTwfn0eCELcUog8YMA4w+Avm8yr+izb/sf8QdqvlhrgosKNCO8t8iKMtv97UBf5VzmKhVHJZ/Xs9YY903JGv5iYN0SStibFA/QIoQ1GGr64UMnueittFfTBSDh1arq6Biolc5zjlElKvRN5kFLCivxyEGkHe9F0Y6ASQZmb7kICSjJptjOqBY2iQdXwgNtnEW8FS9iWM2Fv+j4GCqNbxx6P0p+5BIMeOd1FeW2FuUKtOx7C4sqqi0xarY0/p92/fO62VEfCIqnxuM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 19, 2023 at 01:23:10PM -0800, Rick Edgecombe wrote: > For the current shadow stack implementation, shadow stacks contents can't > easily be provisioned with arbitrary data. This property helps apps > protect themselves better, but also restricts any potential apps that may > want to do exotic things at the expense of a little security. > > The x86 shadow stack feature introduces a new instruction, WRSS, which > can be enabled to write directly to shadow stack permissioned memory from > userspace. Allow it to get enabled via the prctl interface. > > Only enable the userspace WRSS instruction, which allows writes to > userspace shadow stacks from userspace. Do not allow it to be enabled > independently of shadow stack, as HW does not support using WRSS when > shadow stack is disabled. > > From a fault handler perspective, WRSS will behave very similar to WRUSS, > which is treated like a user access from a #PF err code perspective. > > Tested-by: Pengfei Xu > Tested-by: John Allen > Signed-off-by: Rick Edgecombe Reviewed-by: Kees Cook -- Kees Cook