Merge branch 'for_paulus' of master.kernel.org:/pub/scm/linux/kernel/git/galak/powerpc

[pandora-kernel.git] / kernel / ptrace.c

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4e0f0ec..335c5b9 100644 (file)
--- 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);
@@ -148,11 +160,35 @@ int ptrace_may_attach(struct task_struct *task)
 int ptrace_attach(struct task_struct *task)
 {
        int retval;
-       task_lock(task);
+
        retval = -EPERM;
        if (task->pid <= 1)
-               goto bad;
+               goto out;
        if (task->tgid == current->tgid)
+               goto out;
+
+repeat:
+       /*
+        * Nasty, nasty.
+        *
+        * We want to hold both the task-lock and the
+        * tasklist_lock for writing at the same time.
+        * But that's against the rules (tasklist_lock
+        * is taken for reading by interrupts on other
+        * cpu's that may have task_lock).
+        */
+       task_lock(task);
+       local_irq_disable();
+       if (!write_trylock(&tasklist_lock)) {
+               local_irq_enable();
+               task_unlock(task);
+               do {
+                       cpu_relax();
+               } while (!write_can_lock(&tasklist_lock));
+               goto repeat;
+       }
+
+       if (!task->mm)
                goto bad;
        /* the same process cannot be attached many times */
        if (task->ptrace & PT_PTRACED)
@@ -166,21 +202,19 @@ int ptrace_attach(struct task_struct *task)
                                      ? PT_ATTACHED : 0);
        if (capable(CAP_SYS_PTRACE))
                task->ptrace |= PT_PTRACE_CAP;
-       task_unlock(task);
 
-       write_lock_irq(&tasklist_lock);
        __ptrace_link(task, current);
-       write_unlock_irq(&tasklist_lock);
 
        force_sig_specific(SIGSTOP, task);
-       return 0;
 
 bad:
+       write_unlock_irq(&tasklist_lock);
        task_unlock(task);
+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 .. */
@@ -199,6 +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);
@@ -417,21 +452,22 @@ int ptrace_request(struct task_struct *child, long request,
  */
 int ptrace_traceme(void)
 {
-       int ret;
+       int ret = -EPERM;
 
        /*
         * Are we already being traced?
         */
-       if (current->ptrace & PT_PTRACED)
-               return -EPERM;
-       ret = security_ptrace(current->parent, current);
-       if (ret)
-               return -EPERM;
-       /*
-        * Set the ptrace bit in the process ptrace flags.
-        */
-       current->ptrace |= PT_PTRACED;
-       return 0;
+       task_lock(current);
+       if (!(current->ptrace & PT_PTRACED)) {
+               ret = security_ptrace(current->parent, current);
+               /*
+                * Set the ptrace bit in the process ptrace flags.
+                */
+               if (!ret)
+                       current->ptrace |= PT_PTRACED;
+       }
+       task_unlock(current);
+       return ret;
 }
 
 /**