Merge branch 'stackprotector' into core/percpu

17 files changed, 134 insertions, 31 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 73f7fe8fd4d1..ef27aed6ff74 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1340,13 +1340,17 @@ config SECCOMP
 
           If unsure, say Y. Only embedded should say N here.
 
+config CC_STACKPROTECTOR_ALL
+        bool
+
 config CC_STACKPROTECTOR
         bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
-        depends on X86_64 && EXPERIMENTAL && BROKEN
+        depends on X86_64
+        select CC_STACKPROTECTOR_ALL
         help
-         This option turns on the -fstack-protector GCC feature. This
-          feature puts, at the beginning of critical functions, a canary
-          value on the stack just before the return address, and validates
+          This option turns on the -fstack-protector GCC feature. This
+          feature puts, at the beginning of functions, a canary value on
+          the stack just before the return address, and validates
           the value just before actually returning.  Stack based buffer
           overflows (that need to overwrite this return address) now also
           overwrite the canary, which gets detected and the attack is then
@@ -1354,15 +1358,8 @@ config CC_STACKPROTECTOR
 
           This feature requires gcc version 4.2 or above, or a distribution
           gcc with the feature backported. Older versions are automatically
-          detected and for those versions, this configuration option is ignored.
-
-config CC_STACKPROTECTOR_ALL
-        bool "Use stack-protector for all functions"
-        depends on CC_STACKPROTECTOR
-        help
-          Normally, GCC only inserts the canary value protection for
-          functions that use large-ish on-stack buffers. By enabling
-          this option, GCC will be asked to do this for ALL functions.
+          detected and for those versions, this configuration option is
+          ignored. (and a warning is printed during bootup)
 
 source kernel/Kconfig.hz
 
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 10d6cc3fd052..28f111461ca8 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -117,6 +117,7 @@ config DEBUG_RODATA
 config DEBUG_RODATA_TEST
         bool "Testcase for the DEBUG_RODATA feature"
         depends on DEBUG_RODATA
+        default y
         help
           This option enables a testcase for the DEBUG_RODATA
           feature as well as for the change_page_attr() infrastructure.
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index d1a47adb5aec..cacee981d166 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -73,7 +73,7 @@ else
 
         stackp := $(CONFIG_SHELL) $(srctree)/scripts/gcc-x86_64-has-stack-protector.sh
         stackp-$(CONFIG_CC_STACKPROTECTOR) := $(shell $(stackp) \
-                "$(CC)" -fstack-protector )
+                "$(CC)" "-fstack-protector -DGCC_HAS_SP" )
         stackp-$(CONFIG_CC_STACKPROTECTOR_ALL) += $(shell $(stackp) \
                 "$(CC)" -fstack-protector-all )
 
diff --git a/arch/x86/include/asm/pda.h b/arch/x86/include/asm/pda.h
index c31ca048a901..5976cd803e9a 100644
--- a/arch/x86/include/asm/pda.h
+++ b/arch/x86/include/asm/pda.h
@@ -17,11 +17,9 @@ struct x8664_pda {
         unsigned long unused4;
         int unused5;
         unsigned int unused6;           /* 36 was cpunumber */
-#ifdef CONFIG_CC_STACKPROTECTOR
         unsigned long stack_canary;     /* 40 stack canary value */
                                         /* gcc-ABI: this canary MUST be at
                                            offset 40!!! */
-#endif
         short in_bootmem;               /* pda lives in bootmem */
 } ____cacheline_aligned_in_smp;
 
@@ -42,4 +40,6 @@ extern void pda_init(int);
 
 #endif
 
+#define refresh_stack_canary() write_pda(stack_canary, current->stack_canary)
+
 #endif /* _ASM_X86_PDA_H */
diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
new file mode 100644
index 000000000000..c7f0d10bae7b
--- /dev/null
+++ b/arch/x86/include/asm/stackprotector.h
@@ -0,0 +1,39 @@
+#ifndef _ASM_STACKPROTECTOR_H
+#define _ASM_STACKPROTECTOR_H 1
+
+#include <asm/tsc.h>
+#include <asm/pda.h>
+
+/*
+ * Initialize the stackprotector canary value.
+ *
+ * NOTE: this must only be called from functions that never return,
+ * and it must always be inlined.
+ */
+static __always_inline void boot_init_stack_canary(void)
+{
+        u64 canary;
+        u64 tsc;
+
+        /*
+         * If we're the non-boot CPU, nothing set the PDA stack
+         * canary up for us - and if we are the boot CPU we have
+         * a 0 stack canary. This is a good place for updating
+         * it, as we wont ever return from this function (so the
+         * invalid canaries already on the stack wont ever
+         * trigger).
+         *
+         * We both use the random pool and the current TSC as a source
+         * of randomness. The TSC only matters for very early init,
+         * there it already has some randomness on most systems. Later
+         * on during the bootup the random pool has true entropy too.
+         */
+        get_random_bytes(&canary, sizeof(canary));
+        tsc = __native_read_tsc();
+        canary += tsc + (tsc << 32UL);
+
+        current->stack_canary = canary;
+        write_pda(stack_canary, canary);
+}
+
+#endif
diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index d1dc27dba36d..8cadfe9b1194 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -95,6 +95,8 @@ do {									\
              ".globl thread_return\n"                                     \
              "thread_return:\n\t"                                         \
              "movq "__percpu_arg([current_task])",%%rsi\n\t"              \
+             "movq %P[task_canary](%%rsi),%%r8\n\t"                       \
+             "movq %%r8,%%gs:%P[pda_canary]\n\t"                          \
              "movq %P[thread_info](%%rsi),%%r8\n\t"                       \
              LOCK_PREFIX "btr  %[tif_fork],%P[ti_flags](%%r8)\n\t"        \
              "movq %%rax,%%rdi\n\t"                                       \
@@ -106,7 +108,9 @@ do {									\
                [ti_flags] "i" (offsetof(struct thread_info, flags)),      \
                [tif_fork] "i" (TIF_FORK),                                 \
                [thread_info] "i" (offsetof(struct task_struct, stack)),   \
-               [current_task] "m" (per_cpu_var(current_task))             \
+               [task_canary] "i" (offsetof(struct task_struct, stack_canary)),\
+               [current_task] "m" (per_cpu_var(current_task)),            \
+               [pda_canary] "i" (offsetof(struct x8664_pda, stack_canary))\
              : "memory", "cc" __EXTRA_CLOBBER)
 #endif
 
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index d364df03c1d6..eb074530c7d3 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -23,6 +23,7 @@ nostackp := $(call cc-option, -fno-stack-protector)
 CFLAGS_vsyscall_64.o    := $(PROFILING) -g0 $(nostackp)
 CFLAGS_hpet.o           := $(nostackp)
 CFLAGS_tsc.o            := $(nostackp)
+CFLAGS_paravirt.o       := $(nostackp)
 
 obj-y                   := process_$(BITS).o signal.o entry_$(BITS).o
 obj-y                   += traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4523ff88a69d..aa89eabf09e0 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -16,6 +16,7 @@
 
 #include <stdarg.h>
 
+#include <linux/stackprotector.h>
 #include <linux/cpu.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
@@ -117,6 +118,17 @@ static inline void play_dead(void)
 void cpu_idle(void)
 {
         current_thread_info()->status |= TS_POLLING;
+
+        /*
+         * If we're the non-boot CPU, nothing set the PDA stack
+         * canary up for us - and if we are the boot CPU we have
+         * a 0 stack canary. This is a good place for updating
+         * it, as we wont ever return from this function (so the
+         * invalid canaries already on the stack wont ever
+         * trigger):
+         */
+        boot_init_stack_canary();
+
         /* endless idle loop with no priority at all */
         while (1) {
                 tick_nohz_stop_sched_tick(1);
@@ -627,7 +639,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
                   (unsigned long)task_stack_page(next_p) +
                   THREAD_SIZE - KERNEL_STACK_OFFSET);
 #ifdef CONFIG_CC_STACKPROTECTOR
-        write_pda(stack_canary, next_p->stack_canary);
         /*
          * Build time only check to make sure the stack_canary is at
          * offset 40 in the pda; this is a gcc ABI requirement
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 90dfae511a41..37242c405f16 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -26,6 +26,7 @@
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
 #include <linux/kdebug.h>
+#include <linux/magic.h>
 
 #include <asm/system.h>
 #include <asm/desc.h>
@@ -589,6 +590,8 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
         unsigned long address;
         int write, si_code;
         int fault;
+        unsigned long *stackend;
+
 #ifdef CONFIG_X86_64
         unsigned long flags;
         int sig;
@@ -841,6 +844,10 @@ no_context:
 
         show_fault_oops(regs, error_code, address);
 
+        stackend = end_of_stack(tsk);
+        if (*stackend != STACK_END_MAGIC)
+                printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
+
         tsk->thread.cr2 = address;
         tsk->thread.trap_no = 14;
         tsk->thread.error_code = error_code;
diff --git a/include/linux/magic.h b/include/linux/magic.h
index 439f6f3cb0c4..561a5ff92c88 100644
--- a/include/linux/magic.h
+++ b/include/linux/magic.h
@@ -47,4 +47,5 @@
 #define FUTEXFS_SUPER_MAGIC     0xBAD1DEA
 #define INOTIFYFS_SUPER_MAGIC   0x2BAD1DEA
 
+#define STACK_END_MAGIC         0x57AC6E9D
 #endif /* __LINUX_MAGIC_H__ */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4cae9b81a1f8..a85b0cec7d12 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1157,10 +1157,9 @@ struct task_struct {
         pid_t pid;
         pid_t tgid;
 
-#ifdef CONFIG_CC_STACKPROTECTOR
         /* Canary value for the -fstack-protector gcc feature */
         unsigned long stack_canary;
-#endif
+
         /* 
          * pointers to (original) parent process, youngest child, younger sibling,
          * older sibling, respectively.  (p->father can be replaced with 
@@ -2066,6 +2065,19 @@ static inline int object_is_on_stack(void *obj)
 
 extern void thread_info_cache_init(void);
 
+#ifdef CONFIG_DEBUG_STACK_USAGE
+static inline unsigned long stack_not_used(struct task_struct *p)
+{
+        unsigned long *n = end_of_stack(p);
+
+        do {    /* Skip over canary */
+                n++;
+        } while (!*n);
+
+        return (unsigned long)n - (unsigned long)end_of_stack(p);
+}
+#endif
+
 /* set thread flags in other task's structures
  * - see asm/thread_info.h for TIF_xxxx flags available
  */
diff --git a/include/linux/stackprotector.h b/include/linux/stackprotector.h
new file mode 100644
index 000000000000..6f3e54c704c0
--- /dev/null
+++ b/include/linux/stackprotector.h
@@ -0,0 +1,16 @@
+#ifndef _LINUX_STACKPROTECTOR_H
+#define _LINUX_STACKPROTECTOR_H 1
+
+#include <linux/compiler.h>
+#include <linux/sched.h>
+#include <linux/random.h>
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+# include <asm/stackprotector.h>
+#else
+static inline void boot_init_stack_canary(void)
+{
+}
+#endif
+
+#endif
diff --git a/init/main.c b/init/main.c
index 844209453c02..bfe4fb0c9842 100644
--- a/init/main.c
+++ b/init/main.c
@@ -14,6 +14,7 @@
 #include <linux/proc_fs.h>
 #include <linux/kernel.h>
 #include <linux/syscalls.h>
+#include <linux/stackprotector.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
 #include <linux/delay.h>
@@ -539,6 +540,12 @@ asmlinkage void __init start_kernel(void)
          */
         lockdep_init();
         debug_objects_early_init();
+
+        /*
+         * Set up the the initial canary ASAP:
+         */
+        boot_init_stack_canary();
+
         cgroup_init_early();
 
         local_irq_disable();
diff --git a/kernel/exit.c b/kernel/exit.c
index c7740fa3252c..2a803c28df9e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -977,12 +977,9 @@ static void check_stack_usage(void)
 {
         static DEFINE_SPINLOCK(low_water_lock);
         static int lowest_to_date = THREAD_SIZE;
-        unsigned long *n = end_of_stack(current);
         unsigned long free;
 
-        while (*n == 0)
-                n++;
-        free = (unsigned long)n - (unsigned long)end_of_stack(current);
+        free = stack_not_used(current);
 
         if (free >= lowest_to_date)
                 return;
diff --git a/kernel/fork.c b/kernel/fork.c
index 1d68f1255dd8..4a9b318dad0d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -61,6 +61,7 @@
 #include <linux/proc_fs.h>
 #include <linux/blkdev.h>
 #include <trace/sched.h>
+#include <linux/magic.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -212,6 +213,8 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 {
         struct task_struct *tsk;
         struct thread_info *ti;
+        unsigned long *stackend;
+
         int err;
 
         prepare_to_copy(orig);
@@ -237,6 +240,8 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
                 goto out;
 
         setup_thread_stack(tsk, orig);
+        stackend = end_of_stack(tsk);
+        *stackend = STACK_END_MAGIC;    /* for overflow detection */
 
 #ifdef CONFIG_CC_STACKPROTECTOR
         tsk->stack_canary = get_random_int();
diff --git a/kernel/panic.c b/kernel/panic.c
index 2a2ff36ff44d..33cab3de1763 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -74,6 +74,9 @@ NORET_TYPE void panic(const char * fmt, ...)
         vsnprintf(buf, sizeof(buf), fmt, args);
         va_end(args);
         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+        dump_stack();
+#endif
         bust_spinlocks(0);
 
         /*
@@ -355,15 +358,22 @@ EXPORT_SYMBOL(warn_slowpath);
 #endif
 
 #ifdef CONFIG_CC_STACKPROTECTOR
+
+#ifndef GCC_HAS_SP
+#warning You have selected the CONFIG_CC_STACKPROTECTOR option, but the gcc used does not support this.
+#endif
+
 /*
  * Called when gcc's -fstack-protector feature is used, and
  * gcc detects corruption of the on-stack canary value
  */
 void __stack_chk_fail(void)
 {
-        panic("stack-protector: Kernel stack is corrupted");
+        panic("stack-protector: Kernel stack is corrupted in: %p\n",
+                __builtin_return_address(0));
 }
 EXPORT_SYMBOL(__stack_chk_fail);
+
 #endif
 
 core_param(panic, panic_timeout, int, 0644);
diff --git a/kernel/sched.c b/kernel/sched.c
index 8be2c13b50d0..1d2909067040 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5939,12 +5939,7 @@ void sched_show_task(struct task_struct *p)
                 printk(KERN_CONT " %016lx ", thread_saved_pc(p));
 #endif
 #ifdef CONFIG_DEBUG_STACK_USAGE
-        {
-                unsigned long *n = end_of_stack(p);
-                while (!*n)
-                        n++;
-                free = (unsigned long)n - (unsigned long)end_of_stack(p);
-        }
+        free = stack_not_used(p);
 #endif
         printk(KERN_CONT "%5lu %5d %6d\n", free,
                 task_pid_nr(p), task_pid_nr(p->real_parent));