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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z37sm3106644pgl.68.2020.03.26.23.48.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 23:48:23 -0700 (PDT) From: Kees Cook To: Borislav Petkov Subject: [PATCH v5 1/6] x86/elf: Add table to document READ_IMPLIES_EXEC Date: Thu, 26 Mar 2020 23:48:15 -0700 Message-Id: <20200327064820.12602-2-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200327064820.12602-1-keescook@chromium.org> References: <20200327064820.12602-1-keescook@chromium.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200326_234827_697127_550B55E8 X-CRM114-Status: GOOD ( 11.28 ) X-Spam-Score: -0.2 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-0.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:1043 listed in] [list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Jann Horn , Catalin Marinas , x86@kernel.org, Hector Marco-Gisbert , Russell King , linux-kernel@vger.kernel.org, Jason Gunthorpe , Jason Gunthorpe , kernel-hardening@lists.openwall.com, Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Add a table to document the current behavior of READ_IMPLIES_EXEC in preparation for changing the behavior. Signed-off-by: Kees Cook Reviewed-by: Jason Gunthorpe --- arch/x86/include/asm/elf.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 69c0f892e310..ee459d4c3b45 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -281,6 +281,25 @@ extern u32 elf_hwcap2; /* * An executable for which elf_read_implies_exec() returns TRUE will * have the READ_IMPLIES_EXEC personality flag set automatically. + * + * The decision process for determining the results are: + * + *              CPU: | lacks NX*  | has NX, ia32     | has NX, x86_64 | + * ELF:              |            |                  |                | + * ---------------------|------------|------------------|----------------| + * missing PT_GNU_STACK | exec-all   | exec-all         | exec-all       | + * PT_GNU_STACK == RWX  | exec-all   | exec-all         | exec-all       | + * PT_GNU_STACK == RW   | exec-none  | exec-none        | exec-none      | + * + * exec-all : all PROT_READ user mappings are executable, except when + * backed by files on a noexec-filesystem. + * exec-none : only PROT_EXEC user mappings are executable. + * + * *this column has no architectural effect: NX markings are ignored by + * hardware, but may have behavioral effects when "wants X" collides with + * "cannot be X" constraints in memory permission flags, as in + * https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com + * */ #define elf_read_implies_exec(ex, executable_stack) \ (executable_stack != EXSTACK_DISABLE_X)