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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 , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , 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, david@redhat.com, debug@rivosinc.com, Yu-cheng Yu Subject: Re: [PATCH v7 19/41] x86/mm: Check shadow stack page fault errors Message-ID: References: <20230227222957.24501-1-rick.p.edgecombe@intel.com> <20230227222957.24501-20-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230227222957.24501-20-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B4B5F40027 X-Stat-Signature: fhydsump9j799cgf3c1hiqshtwj7d1jy X-HE-Tag: 1677852694-790036 X-HE-Meta: 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 dF91PfwY 6Zm63XU8xDCuiwQe+6tO8G4CfzrNXZ8gc9/GhS0ffOIyVAY2awXVNHBERd1KJZxZoPK/QFwEsvbpALCF0gndkqoN4IVFfCdKKwxBHX7ouN6VPYEavACStwjEWsH40f8VJ+fjIWVIzS0/rGP6mwjjQMly4NmPOLrvE+bZID53Z575Kmo6qZBnvEwcd0bnHT9V0JttLqO30C4LQ6ZjSTr8FrYog9Ljig2BkAxbVeeKJFf2cybkbjjd1fHVJWo1TXylHEG6fPW6BFtvL3zq+qCML44vXew== 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 Mon, Feb 27, 2023 at 02:29:35PM -0800, Rick Edgecombe wrote: > @@ -1310,6 +1324,23 @@ void do_user_addr_fault(struct pt_regs *regs, > > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); > > + /* > + * For conventionally writable pages, a read can be serviced with a > + * read only PTE. But for shadow stack, there isn't a concept of > + * read-only shadow stack memory. If it a PTE has the shadow stack s/it // > + * permission, it can be modified via CALL and RET instructions. So > + * core MM needs to fault in a writable PTE and do things it already > + * does for write faults. > + * > + * Shadow stack accesses (read or write) need to be serviced with > + * shadow stack permission memory, which always include write > + * permissions. So in the case of a shadow stack read access, treat it > + * as a WRITE fault. This will make sure that MM will prepare > + * everything (e.g., break COW) such that maybe_mkwrite() can create a > + * proper shadow stack PTE. > + */ > + if (error_code & X86_PF_SHSTK) > + flags |= FAULT_FLAG_WRITE; > if (error_code & X86_PF_WRITE) > flags |= FAULT_FLAG_WRITE; > if (error_code & X86_PF_INSTR) > -- > 2.17.1 > -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette