Merge branch 'mm-readonly-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull read-only kernel memory updates from Ingo Molnar:
"This tree adds two (security related) enhancements to the kernel's
handling of read-only kernel memory:
- extend read-only kernel memory to a new class of formerly writable
kernel data: 'post-init read-only memory' via the __ro_after_init
attribute, and mark the ARM and x86 vDSO as such read-only memory.
This kind of attribute can be used for data that requires a once
per bootup initialization sequence, but is otherwise never modified
after that point.
This feature was based on the work by PaX Team and Brad Spengler.
(by Kees Cook, the ARM vDSO bits by David Brown.)
- make CONFIG_DEBUG_RODATA always enabled on x86 and remove the
Kconfig option. This simplifies the kernel and also signals that
read-only memory is the default model and a first-class citizen.
(Kees Cook)"
* 'mm-readonly-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
ARM/vdso: Mark the vDSO code read-only after init
x86/vdso: Mark the vDSO code read-only after init
lkdtm: Verify that '__ro_after_init' works correctly
arch: Introduce post-init read-only memory
x86/mm: Always enable CONFIG_DEBUG_RODATA and remove the Kconfig option
mm/init: Add 'rodata=off' boot cmdline parameter to disable read-only kernel mappings
asm-generic: Consolidate mark_rodata_ro()
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9a53c92..0003367 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3491,6 +3491,10 @@
ro [KNL] Mount root device read-only on boot
+ rodata= [KNL]
+ on Mark read-only kernel memory as read-only (default).
+ off Leave read-only kernel memory writable for debugging.
+
root= [KNL] Root filesystem
See name_to_dev_t comment in init/do_mounts.c.
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index d5525bf..9156fc3 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -491,7 +491,6 @@
#endif
#ifdef CONFIG_DEBUG_RODATA
-void mark_rodata_ro(void);
void set_kernel_text_rw(void);
void set_kernel_text_ro(void);
#else
diff --git a/arch/arm/vdso/vdso.S b/arch/arm/vdso/vdso.S
index b2b97e3..a62a7b6 100644
--- a/arch/arm/vdso/vdso.S
+++ b/arch/arm/vdso/vdso.S
@@ -23,9 +23,8 @@
#include <linux/const.h>
#include <asm/page.h>
- __PAGE_ALIGNED_DATA
-
.globl vdso_start, vdso_end
+ .section .data..ro_after_init
.balign PAGE_SIZE
vdso_start:
.incbin "arch/arm/vdso/vdso.so"
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index 7fc294c..22dda61 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -156,8 +156,4 @@
int set_memory_x(unsigned long addr, int numpages);
int set_memory_nx(unsigned long addr, int numpages);
-#ifdef CONFIG_DEBUG_RODATA
-void mark_rodata_ro(void);
-#endif
-
#endif
diff --git a/arch/parisc/include/asm/cache.h b/arch/parisc/include/asm/cache.h
index 3d0e17b..df0f52b 100644
--- a/arch/parisc/include/asm/cache.h
+++ b/arch/parisc/include/asm/cache.h
@@ -22,6 +22,9 @@
#define __read_mostly __attribute__((__section__(".data..read_mostly")))
+/* Read-only memory is marked before mark_rodata_ro() is called. */
+#define __ro_after_init __read_mostly
+
void parisc_cache_init(void); /* initializes cache-flushing */
void disable_sr_hashing_asm(int); /* low level support for above */
void disable_sr_hashing(void); /* turns off space register hashing */
diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm/cacheflush.h
index 845272c..7bd69bd 100644
--- a/arch/parisc/include/asm/cacheflush.h
+++ b/arch/parisc/include/asm/cacheflush.h
@@ -121,10 +121,6 @@
}
}
-#ifdef CONFIG_DEBUG_RODATA
-void mark_rodata_ro(void);
-#endif
-
#include <asm/kmap_types.h>
#define ARCH_HAS_KMAP
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c46662f..b105105 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -303,6 +303,9 @@
config FIX_EARLYCON_MEM
def_bool y
+config DEBUG_RODATA
+ def_bool y
+
config PGTABLE_LEVELS
int
default 4 if X86_64
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 9b18ed9..7816b7b 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -74,28 +74,16 @@
issues with the mapping of the EFI runtime regions into that
table.
-config DEBUG_RODATA
- bool "Write protect kernel read-only data structures"
- default y
- depends on DEBUG_KERNEL
- ---help---
- Mark the kernel read-only data as write-protected in the pagetables,
- in order to catch accidental (and incorrect) writes to such const
- data. This is recommended so that we can catch kernel bugs sooner.
- If in doubt, say "Y".
-
config DEBUG_RODATA_TEST
- bool "Testcase for the DEBUG_RODATA feature"
- depends on DEBUG_RODATA
+ bool "Testcase for the marking rodata read-only"
default y
---help---
- This option enables a testcase for the DEBUG_RODATA
- feature as well as for the change_page_attr() infrastructure.
+ This option enables a testcase for the setting rodata read-only
+ as well as for the change_page_attr() infrastructure.
If in doubt, say "N"
config DEBUG_WX
bool "Warn on W+X mappings at boot"
- depends on DEBUG_RODATA
select X86_PTDUMP_CORE
---help---
Generate a warning if any W+X mappings are found at boot.
diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h
index 0224987..3f69326 100644
--- a/arch/x86/entry/vdso/vdso2c.h
+++ b/arch/x86/entry/vdso/vdso2c.h
@@ -140,7 +140,7 @@
fprintf(outfile, "#include <asm/vdso.h>\n");
fprintf(outfile, "\n");
fprintf(outfile,
- "static unsigned char raw_data[%lu] __page_aligned_data = {",
+ "static unsigned char raw_data[%lu] __ro_after_init __aligned(PAGE_SIZE) = {",
mapping_size);
for (j = 0; j < stripped_len; j++) {
if (j % 10 == 0)
diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index e63aa38..61518cf 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -91,16 +91,10 @@
#define mmio_flush_range(addr, size) clflush_cache_range(addr, size)
-#ifdef CONFIG_DEBUG_RODATA
-void mark_rodata_ro(void);
extern const int rodata_test_data;
extern int kernel_set_to_readonly;
void set_kernel_text_rw(void);
void set_kernel_text_ro(void);
-#else
-static inline void set_kernel_text_rw(void) { }
-static inline void set_kernel_text_ro(void) { }
-#endif
#ifdef CONFIG_DEBUG_RODATA_TEST
int rodata_test(void);
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index c1adf33..bc62e7c 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -17,15 +17,8 @@
}
#endif /* CONFIG_KVM_GUEST */
-#ifdef CONFIG_DEBUG_RODATA
#define KVM_HYPERCALL \
ALTERNATIVE(".byte 0x0f,0x01,0xc1", ".byte 0x0f,0x01,0xd9", X86_FEATURE_VMMCALL)
-#else
-/* On AMD processors, vmcall will generate a trap that we will
- * then rewrite to the appropriate instruction.
- */
-#define KVM_HYPERCALL ".byte 0x0f,0x01,0xc1"
-#endif
/* For KVM hypercalls, a three-byte sequence of either the vmcall or the vmmcall
* instruction. The hypervisor may replace it with something else but only the
diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 0a52424..13b6cdd 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -7,7 +7,7 @@
extern char __brk_base[], __brk_limit[];
extern struct exception_table_entry __stop___ex_table[];
-#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
+#if defined(CONFIG_X86_64)
extern char __end_rodata_hpage_align[];
#endif
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 29408d6..05c9e3f 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -81,9 +81,9 @@
static unsigned long text_ip_addr(unsigned long ip)
{
/*
- * On x86_64, kernel text mappings are mapped read-only with
- * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
- * of the kernel text mapping to modify the kernel text.
+ * On x86_64, kernel text mappings are mapped read-only, so we use
+ * the kernel identity mapping instead of the kernel text mapping
+ * to modify the kernel text.
*
* For 32bit kernels, these mappings are same and we can use
* kernel identity mapping to modify code.
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 44256a6..ed15cd48 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -750,9 +750,7 @@
int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
int err;
-#ifdef CONFIG_DEBUG_RODATA
char opc[BREAK_INSTR_SIZE];
-#endif /* CONFIG_DEBUG_RODATA */
bpt->type = BP_BREAKPOINT;
err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
@@ -761,7 +759,6 @@
return err;
err = probe_kernel_write((char *)bpt->bpt_addr,
arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
-#ifdef CONFIG_DEBUG_RODATA
if (!err)
return err;
/*
@@ -778,13 +775,12 @@
if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE))
return -EINVAL;
bpt->type = BP_POKE_BREAKPOINT;
-#endif /* CONFIG_DEBUG_RODATA */
+
return err;
}
int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
-#ifdef CONFIG_DEBUG_RODATA
int err;
char opc[BREAK_INSTR_SIZE];
@@ -801,8 +797,8 @@
if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))
goto knl_write;
return err;
+
knl_write:
-#endif /* CONFIG_DEBUG_RODATA */
return probe_kernel_write((char *)bpt->bpt_addr,
(char *)bpt->saved_instr, BREAK_INSTR_SIZE);
}
diff --git a/arch/x86/kernel/test_nx.c b/arch/x86/kernel/test_nx.c
index 3f92ce0..27538f1 100644
--- a/arch/x86/kernel/test_nx.c
+++ b/arch/x86/kernel/test_nx.c
@@ -142,7 +142,6 @@
* by the error message
*/
-#ifdef CONFIG_DEBUG_RODATA
/* Test 3: Check if the .rodata section is executable */
if (rodata_test_data != 0xC3) {
printk(KERN_ERR "test_nx: .rodata marker has invalid value\n");
@@ -151,7 +150,6 @@
printk(KERN_ERR "test_nx: .rodata section is executable\n");
ret = -ENODEV;
}
-#endif
#if 0
/* Test 4: Check if the .data section of a module is executable */
diff --git a/arch/x86/kernel/test_rodata.c b/arch/x86/kernel/test_rodata.c
index 5ecbfe5..cb4a01b 100644
--- a/arch/x86/kernel/test_rodata.c
+++ b/arch/x86/kernel/test_rodata.c
@@ -76,5 +76,5 @@
}
MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("Testcase for the DEBUG_RODATA infrastructure");
+MODULE_DESCRIPTION("Testcase for marking rodata as read-only");
MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 74e4bf1..fe133b7 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -41,29 +41,28 @@
jiffies_64 = jiffies;
#endif
-#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
+#if defined(CONFIG_X86_64)
/*
- * On 64-bit, align RODATA to 2MB so that even with CONFIG_DEBUG_RODATA
- * we retain large page mappings for boundaries spanning kernel text, rodata
- * and data sections.
+ * On 64-bit, align RODATA to 2MB so we retain large page mappings for
+ * boundaries spanning kernel text, rodata and data sections.
*
* However, kernel identity mappings will have different RWX permissions
* to the pages mapping to text and to the pages padding (which are freed) the
* text section. Hence kernel identity mappings will be broken to smaller
* pages. For 64-bit, kernel text and kernel identity mappings are different,
- * so we can enable protection checks that come with CONFIG_DEBUG_RODATA,
- * as well as retain 2MB large page mappings for kernel text.
+ * so we can enable protection checks as well as retain 2MB large page
+ * mappings for kernel text.
*/
-#define X64_ALIGN_DEBUG_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
+#define X64_ALIGN_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
-#define X64_ALIGN_DEBUG_RODATA_END \
+#define X64_ALIGN_RODATA_END \
. = ALIGN(HPAGE_SIZE); \
__end_rodata_hpage_align = .;
#else
-#define X64_ALIGN_DEBUG_RODATA_BEGIN
-#define X64_ALIGN_DEBUG_RODATA_END
+#define X64_ALIGN_RODATA_BEGIN
+#define X64_ALIGN_RODATA_END
#endif
@@ -112,13 +111,11 @@
EXCEPTION_TABLE(16) :text = 0x9090
-#if defined(CONFIG_DEBUG_RODATA)
/* .text should occupy whole number of pages */
. = ALIGN(PAGE_SIZE);
-#endif
- X64_ALIGN_DEBUG_RODATA_BEGIN
+ X64_ALIGN_RODATA_BEGIN
RO_DATA(PAGE_SIZE)
- X64_ALIGN_DEBUG_RODATA_END
+ X64_ALIGN_RODATA_END
/* Data */
.data : AT(ADDR(.data) - LOAD_OFFSET) {
diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index cb4ef3d..2ebfbaf 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -871,7 +871,6 @@
return flag;
}
-#ifdef CONFIG_DEBUG_RODATA
const int rodata_test_data = 0xC3;
EXPORT_SYMBOL_GPL(rodata_test_data);
@@ -960,5 +959,3 @@
if (__supported_pte_mask & _PAGE_NX)
debug_checkwx();
}
-#endif
-
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5488d21..a40b755 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1074,7 +1074,6 @@
mem_init_print_info(NULL);
}
-#ifdef CONFIG_DEBUG_RODATA
const int rodata_test_data = 0xC3;
EXPORT_SYMBOL_GPL(rodata_test_data);
@@ -1166,8 +1165,6 @@
debug_checkwx();
}
-#endif
-
int kern_addr_valid(unsigned long addr)
{
unsigned long above = ((long)addr) >> __VIRTUAL_MASK_SHIFT;
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 9cf96d8..1c37e65 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -283,7 +283,7 @@
__pa_symbol(__end_rodata) >> PAGE_SHIFT))
pgprot_val(forbidden) |= _PAGE_RW;
-#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
+#if defined(CONFIG_X86_64)
/*
* Once the kernel maps the text as RO (kernel_set_to_readonly is set),
* kernel text mappings for the large page aligned text, rodata sections
diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 11fdadc..2a6eaf1 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -103,6 +103,7 @@
CT_EXEC_USERSPACE,
CT_ACCESS_USERSPACE,
CT_WRITE_RO,
+ CT_WRITE_RO_AFTER_INIT,
CT_WRITE_KERN,
};
@@ -140,6 +141,7 @@
"EXEC_USERSPACE",
"ACCESS_USERSPACE",
"WRITE_RO",
+ "WRITE_RO_AFTER_INIT",
"WRITE_KERN",
};
@@ -162,6 +164,7 @@
static u8 data_area[EXEC_SIZE];
static const unsigned long rodata = 0xAA55AA55;
+static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
module_param(recur_count, int, 0644);
MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test");
@@ -503,11 +506,28 @@
break;
}
case CT_WRITE_RO: {
- unsigned long *ptr;
+ /* Explicitly cast away "const" for the test. */
+ unsigned long *ptr = (unsigned long *)&rodata;
- ptr = (unsigned long *)&rodata;
+ pr_info("attempting bad rodata write at %p\n", ptr);
+ *ptr ^= 0xabcd1234;
- pr_info("attempting bad write at %p\n", ptr);
+ break;
+ }
+ case CT_WRITE_RO_AFTER_INIT: {
+ unsigned long *ptr = &ro_after_init;
+
+ /*
+ * Verify we were written to during init. Since an Oops
+ * is considered a "success", a failure is to just skip the
+ * real test.
+ */
+ if ((*ptr & 0xAA) != 0xAA) {
+ pr_info("%p was NOT written during init!?\n", ptr);
+ break;
+ }
+
+ pr_info("attempting bad ro_after_init write at %p\n", ptr);
*ptr ^= 0xabcd1234;
break;
@@ -817,6 +837,9 @@
int n_debugfs_entries = 1; /* Assume only the direct entry */
int i;
+ /* Make sure we can write to __ro_after_init values during __init */
+ ro_after_init |= 0xAA;
+
/* Register debugfs interface */
lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
if (!lkdtm_debugfs_root) {
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index c4bd0e2..772c784 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -256,6 +256,7 @@
.rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start_rodata) = .; \
*(.rodata) *(.rodata.*) \
+ *(.data..ro_after_init) /* Read only after init */ \
*(__vermagic) /* Kernel version magic */ \
. = ALIGN(8); \
VMLINUX_SYMBOL(__start___tracepoints_ptrs) = .; \
diff --git a/include/linux/cache.h b/include/linux/cache.h
index 17e7e82..1be04f8 100644
--- a/include/linux/cache.h
+++ b/include/linux/cache.h
@@ -12,10 +12,24 @@
#define SMP_CACHE_BYTES L1_CACHE_BYTES
#endif
+/*
+ * __read_mostly is used to keep rarely changing variables out of frequently
+ * updated cachelines. If an architecture doesn't support it, ignore the
+ * hint.
+ */
#ifndef __read_mostly
#define __read_mostly
#endif
+/*
+ * __ro_after_init is used to mark things that are read-only after init (i.e.
+ * after mark_rodata_ro() has been called). These are effectively read-only,
+ * but may get written to during init, so can't live in .rodata (via "const").
+ */
+#ifndef __ro_after_init
+#define __ro_after_init __attribute__((__section__(".data..ro_after_init")))
+#endif
+
#ifndef ____cacheline_aligned
#define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES)))
#endif
diff --git a/include/linux/init.h b/include/linux/init.h
index b449f37..aedb254 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -142,6 +142,10 @@
void __init load_default_modules(void);
int __init init_rootfs(void);
+#ifdef CONFIG_DEBUG_RODATA
+void mark_rodata_ro(void);
+#endif
+
extern void (*late_time_init)(void);
extern bool initcall_debug;
diff --git a/init/main.c b/init/main.c
index b3008bc..7c27de4 100644
--- a/init/main.c
+++ b/init/main.c
@@ -93,9 +93,6 @@
extern void init_IRQ(void);
extern void fork_init(void);
extern void radix_tree_init(void);
-#ifndef CONFIG_DEBUG_RODATA
-static inline void mark_rodata_ro(void) { }
-#endif
/*
* Debug helper: via this flag we know that we are in 'early bootup code'
@@ -924,6 +921,28 @@
static noinline void __init kernel_init_freeable(void);
+#ifdef CONFIG_DEBUG_RODATA
+static bool rodata_enabled = true;
+static int __init set_debug_rodata(char *str)
+{
+ return strtobool(str, &rodata_enabled);
+}
+__setup("rodata=", set_debug_rodata);
+
+static void mark_readonly(void)
+{
+ if (rodata_enabled)
+ mark_rodata_ro();
+ else
+ pr_info("Kernel memory protection disabled.\n");
+}
+#else
+static inline void mark_readonly(void)
+{
+ pr_warn("This architecture does not have kernel memory protection.\n");
+}
+#endif
+
static int __ref kernel_init(void *unused)
{
int ret;
@@ -932,7 +951,7 @@
/* need to finish all async __init code before freeing the memory */
async_synchronize_full();
free_initmem();
- mark_rodata_ro();
+ mark_readonly();
system_state = SYSTEM_RUNNING;
numa_default_policy();
diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c
index e1dbf4a..90ff129 100644
--- a/kernel/debug/kdb/kdb_bp.c
+++ b/kernel/debug/kdb/kdb_bp.c
@@ -153,13 +153,11 @@
} else {
kdb_printf("%s: failed to set breakpoint at 0x%lx\n",
__func__, bp->bp_addr);
-#ifdef CONFIG_DEBUG_RODATA
if (!bp->bp_type) {
kdb_printf("Software breakpoints are unavailable.\n"
- " Change the kernel CONFIG_DEBUG_RODATA=n\n"
+ " Boot the kernel with rodata=off\n"
" OR use hw breaks: help bph\n");
}
-#endif
return 1;
}
return 0;