[PATCH v2 3/6] RISC-V: Enforce protections for kernel sections early

From: Atish Patra <atish.patra@wdc.com>
To: linux-kernel@vger.kernel.org
Cc: Atish Patra <atish.patra@wdc.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Andrew Morton <akpm@linux-foundation.org>,
	Anup Patel <anup@brainfault.org>,
	Ard Biesheuvel <ardb@kernel.org>, Borislav Petkov <bp@suse.de>,
	Greentime Hu <greentime.hu@sifive.com>,
	Kees Cook <keescook@chromium.org>,
	linux-riscv@lists.infradead.org,
	Michel Lespinasse <walken@google.com>,
	Mike Rapoport <rppt@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Zong Li <zong.li@sifive.com>
Subject: [PATCH v2 3/6] RISC-V: Enforce protections for kernel sections early
Date: Mon, 26 Oct 2020 16:02:51 -0700	[thread overview]
Message-ID: <20201026230254.911912-4-atish.patra@wdc.com> (raw)
In-Reply-To: <20201026230254.911912-1-atish.patra@wdc.com>

Currently, all memblocks are mapped with PAGE_KERNEL_EXEC and the strict
permissions are only enforced after /init starts. This leaves the kernel
vulnerable from possible buggy built-in modules.

Apply permissions to individual sections as early as possible.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/set_memory.h |  2 ++
 arch/riscv/kernel/setup.c           |  2 ++
 arch/riscv/mm/init.c                | 11 +++++++++--
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
index 4c5bae7ca01c..4cc3a4e2afd3 100644
--- a/arch/riscv/include/asm/set_memory.h
+++ b/arch/riscv/include/asm/set_memory.h
@@ -15,11 +15,13 @@ int set_memory_ro(unsigned long addr, int numpages);
 int set_memory_rw(unsigned long addr, int numpages);
 int set_memory_x(unsigned long addr, int numpages);
 int set_memory_nx(unsigned long addr, int numpages);
+void protect_kernel_text_data(void);
 #else
 static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; }
 static inline int set_memory_rw(unsigned long addr, int numpages) { return 0; }
 static inline int set_memory_x(unsigned long addr, int numpages) { return 0; }
 static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; }
+static inline void protect_kernel_text_data(void) {};
 #endif
 
 int set_direct_map_invalid_noflush(struct page *page);
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 7d6a04ae3929..b722c5bf892c 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -22,6 +22,7 @@
 #include <asm/cpu_ops.h>
 #include <asm/early_ioremap.h>
 #include <asm/setup.h>
+#include <asm/set_memory.h>
 #include <asm/sections.h>
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
@@ -92,6 +93,7 @@ void __init setup_arch(char **cmdline_p)
 #if IS_ENABLED(CONFIG_RISCV_SBI)
 	sbi_init();
 #endif
+	protect_kernel_text_data();
 #ifdef CONFIG_SWIOTLB
 	swiotlb_init(1);
 #endif
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index ea933b789a88..5f196f8158d4 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -608,7 +608,7 @@ static inline void setup_vm_final(void)
 #endif /* CONFIG_MMU */
 
 #ifdef CONFIG_STRICT_KERNEL_RWX
-void mark_rodata_ro(void)
+void protect_kernel_text_data(void)
 {
 	unsigned long text_start = (unsigned long)_text;
 	unsigned long text_end = (unsigned long)_etext;
@@ -617,9 +617,16 @@ void mark_rodata_ro(void)
 	unsigned long max_low = (unsigned long)(__va(PFN_PHYS(max_low_pfn)));
 
 	set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT);
-	set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
 	set_memory_nx(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
 	set_memory_nx(data_start, (max_low - data_start) >> PAGE_SHIFT);
+}
+
+void mark_rodata_ro(void)
+{
+	unsigned long rodata_start = (unsigned long)__start_rodata;
+	unsigned long data_start = (unsigned long)_data;
+
+	set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
 
 	debug_checkwx();
 }
-- 
2.25.1

