Yama: add additional ptrace scopes

[~andy/linux] / security / yama / yama_lsm.c

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 573723843a04fa3c3701826519652cea3b46029d..afb04cbb697117e1509de2ff107cfedd53c05ad8 100644 (file)
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -18,7 +18,12 @@
 #include <linux/prctl.h>
 #include <linux/ratelimit.h>
 
-static int ptrace_scope = 1;
+#define YAMA_SCOPE_DISABLED    0
+#define YAMA_SCOPE_RELATIONAL  1
+#define YAMA_SCOPE_CAPABILITY  2
+#define YAMA_SCOPE_NO_ATTACH   3
+
+static int ptrace_scope = YAMA_SCOPE_RELATIONAL;
 
 /* describe a ptrace relationship for potential exception */
 struct ptrace_relation {
@@ -251,17 +256,32 @@ static int yama_ptrace_access_check(struct task_struct *child,
                return rc;
 
        /* require ptrace target be a child of ptracer on attach */
-       if (mode == PTRACE_MODE_ATTACH &&
-           ptrace_scope &&
-           !task_is_descendant(current, child) &&
-           !ptracer_exception_found(current, child) &&
-           !capable(CAP_SYS_PTRACE))
-               rc = -EPERM;
+       if (mode == PTRACE_MODE_ATTACH) {
+               switch (ptrace_scope) {
+               case YAMA_SCOPE_DISABLED:
+                       /* No additional restrictions. */
+                       break;
+               case YAMA_SCOPE_RELATIONAL:
+                       if (!task_is_descendant(current, child) &&
+                           !ptracer_exception_found(current, child) &&
+                           !capable(CAP_SYS_PTRACE))
+                               rc = -EPERM;
+                       break;
+               case YAMA_SCOPE_CAPABILITY:
+                       if (!capable(CAP_SYS_PTRACE))
+                               rc = -EPERM;
+                       break;
+               case YAMA_SCOPE_NO_ATTACH:
+               default:
+                       rc = -EPERM;
+                       break;
+               }
+       }
 
        if (rc) {
                char name[sizeof(current->comm)];
-               printk_ratelimited(KERN_NOTICE "ptrace of non-child"
-                       " pid %d was attempted by: %s (pid %d)\n",
+               printk_ratelimited(KERN_NOTICE
+                       "ptrace of pid %d was attempted by: %s (pid %d)\n",
                        child->pid,
                        get_task_comm(name, current),
                        current->pid);
@@ -279,8 +299,28 @@ static struct security_operations yama_ops = {
 };
 
 #ifdef CONFIG_SYSCTL
+static int yama_dointvec_minmax(struct ctl_table *table, int write,
+                               void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+       int rc;
+
+       if (write && !capable(CAP_SYS_PTRACE))
+               return -EPERM;
+
+       rc = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+       if (rc)
+               return rc;
+
+       /* Lock the max value if it ever gets set. */
+       if (write && *(int *)table->data == *(int *)table->extra2)
+               table->extra1 = table->extra2;
+
+       return rc;
+}
+
 static int zero;
 static int one = 1;
+static int max_scope = YAMA_SCOPE_NO_ATTACH;
 
 struct ctl_path yama_sysctl_path[] = {
        { .procname = "kernel", },
@@ -294,9 +334,9 @@ static struct ctl_table yama_sysctl_table[] = {
                .data           = &ptrace_scope,
                .maxlen         = sizeof(int),
                .mode           = 0644,
-               .proc_handler   = proc_dointvec_minmax,
+               .proc_handler   = yama_dointvec_minmax,
                .extra1         = &zero,
-               .extra2         = &one,
+               .extra2         = &max_scope,
        },
        { }
 };