4 files changed, 47 insertions, 0 deletions

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 574067194f38..11d5ceda5bb0 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -34,6 +34,7 @@ show up in /proc/sys/kernel:
 - hotplug
 - java-appletviewer           [ binfmt_java, obsolete ]
 - java-interpreter            [ binfmt_java, obsolete ]
+- kptr_restrict
 - kstack_depth_to_print       [ X86 only ]
 - l2cr                        [ PPC only ]
 - modprobe                    ==> Documentation/debugging-modules.txt
@@ -261,6 +262,19 @@ This flag controls the L2 cache of G3 processor boards. If
 
 ==============================================================
 
+kptr_restrict:
+
+This toggle indicates whether restrictions are placed on
+exposing kernel addresses via /proc and other interfaces.  When
+kptr_restrict is set to (0), there are no restrictions.  When
+kptr_restrict is set to (1), the default, kernel pointers
+printed using the %pK format specifier will be replaced with 0's
+unless the user has CAP_SYSLOG.  When kptr_restrict is set to
+(2), kernel pointers printed using %pK will be replaced with 0's
+regardless of privileges.
+
+==============================================================
+
 kstack_depth_to_print: (X86 only)
 
 Controls the number of words to print when dumping the raw
diff --git a/include/linux/printk.h b/include/linux/printk.h
index b772ca5fbdf0..9adfba6ec28a 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -83,6 +83,7 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 
 extern int printk_delay_msec;
 extern int dmesg_restrict;
+extern int kptr_restrict;
 
 /*
  * Print a one-time message (analogous to WARN_ONCE() et al):
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ae5cbb1e3ced..c6811ee2092b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -24,6 +24,7 @@
 #include <linux/slab.h>
 #include <linux/sysctl.h>
 #include <linux/signal.h>
+#include <linux/printk.h>
 #include <linux/proc_fs.h>
 #include <linux/security.h>
 #include <linux/ctype.h>
@@ -710,6 +711,15 @@ static struct ctl_table kern_table[] = {
                 .extra1         = &zero,
                 .extra2         = &one,
         },
+        {
+                .procname       = "kptr_restrict",
+                .data           = &kptr_restrict,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &zero,
+                .extra2         = &two,
+        },
 #endif
         {
                 .procname       = "ngroups_max",
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c150d3dafff4..6ff38524ec16 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -936,6 +936,8 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
         return string(buf, end, uuid, spec);
 }
 
+int kptr_restrict = 1;
+
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
@@ -979,6 +981,7 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
  *       Implements a "recursive vsnprintf".
  *       Do not use this feature without some mechanism to verify the
  *       correctness of the format string and va_list arguments.
+ * - 'K' For a kernel pointer that should be hidden from unprivileged users
  *
  * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
  * function pointers are really function descriptors, which contain a
@@ -1035,6 +1038,25 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
                 return buf + vsnprintf(buf, end - buf,
                                        ((struct va_format *)ptr)->fmt,
                                        *(((struct va_format *)ptr)->va));
+        case 'K':
+                /*
+                 * %pK cannot be used in IRQ context because its test
+                 * for CAP_SYSLOG would be meaningless.
+                 */
+                if (in_irq() || in_serving_softirq() || in_nmi()) {
+                        if (spec.field_width == -1)
+                                spec.field_width = 2 * sizeof(void *);
+                        return string(buf, end, "pK-error", spec);
+                } else if ((kptr_restrict == 0) ||
+                         (kptr_restrict == 1 &&
+                          has_capability_noaudit(current, CAP_SYSLOG)))
+                        break;
+
+                if (spec.field_width == -1) {
+                        spec.field_width = 2 * sizeof(void *);
+                        spec.flags |= ZEROPAD;
+                }
+                return number(buf, end, 0, spec);
         }
         spec.flags |= SMALL;
         if (spec.field_width == -1) {