1 files changed, 19 insertions, 4 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 921c22ad16e4..335c5b932e14 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -120,8 +120,18 @@ int ptrace_check_attach(struct task_struct *child, int kill)
 
 static int may_attach(struct task_struct *task)
 {
-        if (!task->mm)
-                return -EPERM;
+        /* May we inspect the given task?
+         * This check is used both for attaching with ptrace
+         * and for allowing access to sensitive information in /proc.
+         *
+         * ptrace_attach denies several cases that /proc allows
+         * because setting up the necessary parent/child relationship
+         * or halting the specified task is impossible.
+         */
+        int dumpable = 0;
+        /* Don't let security modules deny introspection */
+        if (task == current)
+                return 0;
         if (((current->uid != task->euid) ||
              (current->uid != task->suid) ||
              (current->uid != task->uid) ||
@@ -130,7 +140,9 @@ static int may_attach(struct task_struct *task)
              (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
                 return -EPERM;
         smp_rmb();
-        if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
+        if (task->mm)
+                dumpable = task->mm->dumpable;
+        if (!dumpable && !capable(CAP_SYS_PTRACE))
                 return -EPERM;
 
         return security_ptrace(current, task);
@@ -176,6 +188,8 @@ repeat:
                 goto repeat;
         }
 
+        if (!task->mm)
+                goto bad;
         /* the same process cannot be attached many times */
         if (task->ptrace & PT_PTRACED)
                 goto bad;
@@ -200,7 +214,7 @@ out:
         return retval;
 }
 
-void __ptrace_detach(struct task_struct *child, unsigned int data)
+static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
 {
         child->exit_code = data;
         /* .. re-parent .. */
@@ -219,6 +233,7 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
         ptrace_disable(child);
 
         write_lock_irq(&tasklist_lock);
+        /* protect against de_thread()->release_task() */
         if (child->ptrace)
                 __ptrace_detach(child, data);
         write_unlock_irq(&tasklist_lock);