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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, szabolcs.nagy@arm.com Cc: rick.p.edgecombe@intel.com Subject: [PATCH v8 27/40] x86/mm: Warn if create Write=0,Dirty=1 with raw prot Date: Sat, 18 Mar 2023 17:15:22 -0700 Message-Id: <20230319001535.23210-28-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230319001535.23210-1-rick.p.edgecombe@intel.com> References: <20230319001535.23210-1-rick.p.edgecombe@intel.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B244C1C0014 X-Rspam-User: X-Stat-Signature: sjdrbwkxkzgsuq3w1p6m4zizhuz5i1sc X-HE-Tag: 1679185000-617891 X-HE-Meta: U2FsdGVkX1+DKBOZV8KfrUp7q0ys8GI6QFebqqwNIB9lM6IEm2vL4nFDcbsAkZOfcexhIXfHsmL5xIq/ON/Y9fNH/gdHgPl7lnM0CQFioaIue1vEK+7bu2D2xlqlEmYflaTA1JNZ9qSocmFdbFv6sReqhDWmm+UJz3r3HEX4LnUREMArAKGbSqAj7V+Wj71K5nd+jEOasiHZL3Srx6HiBJ7Dx5k1ePVMAS/4SDngxxgFSyb4kH5JJYVv7YGQqkkN7jBXBILeIk0p6MoS+HnJbNdhn5aEJF5t36gvGYkU93LAbHwnQsCPvhGUuc7U8GE1CI3U/0pbYJ/1BBflZOJsHZCSR34r+f/a/gFGsA5G3krCkRcoN8ALbIctJXuKldHKennQUOY+hapWXJICDuCzQ+iLJ22/D9gSKjX5ipJEs03r3YMamJHbPg3mudmWJ4sLJ4dnkI4ASQFhiuyUQdNVsWEP5/yShJIyYDMtiOOLtiRSAZfMksrzhsFDHM4JpNVNV+DctP9tlaiMvP+kD+e6va5C2WdoKErQyamQX8IPUoDE2o/zQj+Alw1p31AXla60X06JOUjv9z8X4OJyQEgjfFNC40QMpqgV0MABu9jQ0hDwjZjR5e8vPHm2wIVDMJ9nelfXZDB2pVsD8mrlGxPOFxvEkL6p4r8FEAOChjEAcGN71xhG12fiji50RDGya+6QTNvFIA8k6NRUrX2ePkFDwwFTVs8yFQuBR1MdHXksmLteNVDHlruy9rplHrOGtsX5HxSmdG9hT/uqs6A80YEDKu57eiGOTEQTEbmcBAqm+kYEXDv0+xBudhnHXbbVPK8n0x+1jF2E4UJxVkjLTNej+ODEPIIrRFGsEKStBZm+eHHLVZvbhkpb3UEVYohvjRp3fIwG8+Jg2JN4WzN3KBAV4AGY5RnnVZJ5zcFpl+ECm9hKMCn0SkdL6396jsz/F/t5dvNrBKbzFWDdWgaEs67 jecEjNJU t0s+HnlORuNBmC4xU3J+FSZx9oenZDWnkLjoj5lROf+Jn2G6xvsoED+CW+qxPdBEJvEsRBT0/1Wl5zTzT4Rmpe2aPuA4AbmE+q4+FFx7KJeNqNG16zmSCCHvkzkYLqeXM/y4LIpC+ERMfzxDETZ8oc9p+EhI010T69ngQVL+BWXLFj9ntsqQwtkmJrJ8VHRbM5zl+xqQakWpAYbJfCidDLF8LJbnxuL+SQTdBK11IX6rjXwUxYioW4bk65eRQFYs8i+aY1JxZDxr7HtaNaoLBhIjo+jCLaKrjzcEFbGmCU9Z2d/J2xXClu5goN1H1a9CXwsnwx81O71G1xGS7fZOdmOzYEsCqmkxtf1Cb 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 in 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, like, for example, set_memory_rox() did. Signed-off-by: Rick Edgecombe Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook --- v8: - Update commit log verbiage (Boris) 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 e5b3dce0d9fe..7142f99d3fbb 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) { -- 2.17.1