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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 , Borislav Petkov , 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 Cc: rick.p.edgecombe@intel.com Subject: [PATCH v6 27/41] x86/mm: Warn if create Write=0,Dirty=1 with raw prot Date: Sat, 18 Feb 2023 13:14:19 -0800 Message-Id: <20230218211433.26859-28-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230218211433.26859-1-rick.p.edgecombe@intel.com> References: <20230218211433.26859-1-rick.p.edgecombe@intel.com> X-Rspamd-Queue-Id: E8339180007 X-Stat-Signature: wt6oeyt3ffzmzaystno79ifz4syn7wh8 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1676754981-341520 X-HE-Meta: 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 ugS89Xml apESETbuBi7XxARLhW8Ol/QTMwrQg8P1ZhXtDT+7KrlZUEpbcBkVIUrNWlh6taGhGo6QHuwzvI6twRIEOMNhpFRFpN+OhCUJUbNeuyGMnVrfKDsEJdtX0Kc+VAsMROIPcKcfXAIJvacxszA4xVqvQfkzXQ389cWksJYcj4wPQJyx4TGMmMPNoUCUpKn/PMDNOudjDV/gvsQWjmvA= 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: When user shadow stack is use, Write=0,Dirty=1 is treated by the CPU as shadow stack memory. So for shadow stack memory this bit combination is valid, but when Dirty=1,Write=1 (conventionally writable) memory is being write protected, the kernel has been taught to transition the Dirty=1 bit to SavedDirty=1, to avoid inadvertently creating shadow stack memory. It does this inside pte_wrprotect() because it knows the PTE is not intended to be a writable shadow stack entry, it is supposed to be write protected. However, when a PTE is created by a raw prot using mk_pte(), mk_pte() can't know whether to adjust Dirty=1 to SavedDirty=1. It can't distinguish between the caller intending to create a shadow stack PTE or needing the SavedDirty shift. The kernel has been updated to not do this, and so Write=0,Dirty=1 memory should only be created by the pte_mkfoo() helpers. Add a warning to make sure no new mk_pte() start doing this. Tested-by: Pengfei Xu Signed-off-by: Rick Edgecombe --- v6: - New patch (Note, this has already been a useful warning, it caught the newly added set_memory_rox() doing this) --- arch/x86/include/asm/pgtable.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index f3dc16fc4389..db8fe5511c74 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1032,7 +1032,15 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) * (Currently stuck as a macro because of indirect forward reference * to linux/mm.h:page_to_nid()) */ -#define mk_pte(page, pgprot) pfn_pte(page_to_pfn(page), (pgprot)) +#define mk_pte(page, pgprot) \ +({ \ + pgprot_t __pgprot = pgprot; \ + \ + WARN_ON_ONCE(cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && \ + (pgprot_val(__pgprot) & (_PAGE_DIRTY | _PAGE_RW)) == \ + _PAGE_DIRTY); \ + pfn_pte(page_to_pfn(page), __pgprot); \ +}) static inline int pmd_bad(pmd_t pmd) {