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Wed, 26 Feb 2020 01:36:35 -0500 (EST) From: Russell Currey To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v5 8/8] powerpc/mm: Disable set_memory() routines when strict RWX isn't enabled Date: Wed, 26 Feb 2020 17:35:51 +1100 Message-Id: <20200226063551.65363-9-ruscur@russell.cc> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200226063551.65363-1-ruscur@russell.cc> References: <20200226063551.65363-1-ruscur@russell.cc> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ajd@linux.ibm.com, kernel-hardening@lists.openwall.com, jniethe5@gmail.com, Russell Currey , npiggin@gmail.com, joel@jms.id.au, dja@axtens.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" There are a couple of reasons that the set_memory() functions are problematic when STRICT_KERNEL_RWX isn't enabled: - The linear mapping is a different size and apply_to_page_range() may modify a giant section, breaking everything - patch_instruction() doesn't know to work around a page being marked RO, and will subsequently crash The latter can be replicated by building a kernel with the set_memory() patches but with STRICT_KERNEL_RWX off and running ftracetest. Reported-by: Jordan Niethe Signed-off-by: Russell Currey --- v5: Apply to both set_memory_attr() and change_memory_attr() v4: New arch/powerpc/mm/pageattr.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c index ee6b5e3b7604..49b8e2e0581d 100644 --- a/arch/powerpc/mm/pageattr.c +++ b/arch/powerpc/mm/pageattr.c @@ -64,13 +64,18 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) int change_memory_attr(unsigned long addr, int numpages, long action) { - unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); - unsigned long sz = numpages * PAGE_SIZE; + unsigned long start, size; + + if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) + return 0; if (!numpages) return 0; - return apply_to_page_range(&init_mm, start, sz, change_page_attr, (void *)action); + start = ALIGN_DOWN(addr, PAGE_SIZE); + size = numpages * PAGE_SIZE; + + return apply_to_page_range(&init_mm, start, size, change_page_attr, (void *)action); } /* @@ -96,12 +101,17 @@ static int set_page_attr(pte_t *ptep, unsigned long addr, void *data) int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot) { - unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); - unsigned long sz = numpages * PAGE_SIZE; + unsigned long start, size; + + if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) + return 0; if (!numpages) return 0; - return apply_to_page_range(&init_mm, start, sz, set_page_attr, + start = ALIGN_DOWN(addr, PAGE_SIZE); + size = numpages * PAGE_SIZE; + + return apply_to_page_range(&init_mm, start, size, set_page_attr, (void *)pgprot_val(prot)); } -- 2.25.1