1 files changed, 59 insertions, 104 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index f6d8b8cb5e34..082c320e4dbf 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -167,67 +167,82 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode)
 int ptrace_attach(struct task_struct *task)
 {
         int retval;
-        unsigned long flags;
 
         audit_ptrace(task);
 
         retval = -EPERM;
+        if (unlikely(task->flags & PF_KTHREAD))
+                goto out;
         if (same_thread_group(task, current))
                 goto out;
 
-        /* Protect the target's credential calculations against our
+        /*
+         * Protect exec's credential calculations against our interference;
          * interference; SUID, SGID and LSM creds get determined differently
          * under ptrace.
          */
-        retval = mutex_lock_interruptible(&task->cred_guard_mutex);
-        if (retval  < 0)
+        retval = -ERESTARTNOINTR;
+        if (mutex_lock_interruptible(&task->cred_guard_mutex))
                 goto out;
 
-        retval = -EPERM;
-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);
-        if (!write_trylock_irqsave(&tasklist_lock, flags)) {
-                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)
-                goto bad;
         retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
+        task_unlock(task);
         if (retval)
-                goto bad;
+                goto unlock_creds;
 
-        /* Go */
-        task->ptrace |= PT_PTRACED;
+        write_lock_irq(&tasklist_lock);
+        retval = -EPERM;
+        if (unlikely(task->exit_state))
+                goto unlock_tasklist;
+        if (task->ptrace)
+                goto unlock_tasklist;
+
+        task->ptrace = PT_PTRACED;
         if (capable(CAP_SYS_PTRACE))
                 task->ptrace |= PT_PTRACE_CAP;
 
         __ptrace_link(task, current);
-
         send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
-bad:
-        write_unlock_irqrestore(&tasklist_lock, flags);
-        task_unlock(task);
+
+        retval = 0;
+unlock_tasklist:
+        write_unlock_irq(&tasklist_lock);
+unlock_creds:
         mutex_unlock(&task->cred_guard_mutex);
 out:
         return retval;
 }
 
+/**
+ * ptrace_traceme  --  helper for PTRACE_TRACEME
+ *
+ * Performs checks and sets PT_PTRACED.
+ * Should be used by all ptrace implementations for PTRACE_TRACEME.
+ */
+int ptrace_traceme(void)
+{
+        int ret = -EPERM;
+
+        write_lock_irq(&tasklist_lock);
+        /* Are we already being traced? */
+        if (!current->ptrace) {
+                ret = security_ptrace_traceme(current->parent);
+                /*
+                 * Check PF_EXITING to ensure ->real_parent has not passed
+                 * exit_ptrace(). Otherwise we don't report the error but
+                 * pretend ->real_parent untraces us right after return.
+                 */
+                if (!ret && !(current->real_parent->flags & PF_EXITING)) {
+                        current->ptrace = PT_PTRACED;
+                        __ptrace_link(current, current->real_parent);
+                }
+        }
+        write_unlock_irq(&tasklist_lock);
+
+        return ret;
+}
+
 /*
  * Called with irqs disabled, returns true if childs should reap themselves.
  */
@@ -409,37 +424,33 @@ static int ptrace_setoptions(struct task_struct *child, long data)
 
 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 {
+        unsigned long flags;
         int error = -ESRCH;
 
-        read_lock(&tasklist_lock);
-        if (likely(child->sighand != NULL)) {
+        if (lock_task_sighand(child, &flags)) {
                 error = -EINVAL;
-                spin_lock_irq(&child->sighand->siglock);
                 if (likely(child->last_siginfo != NULL)) {
                         *info = *child->last_siginfo;
                         error = 0;
                 }
-                spin_unlock_irq(&child->sighand->siglock);
+                unlock_task_sighand(child, &flags);
         }
-        read_unlock(&tasklist_lock);
         return error;
 }
 
 static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 {
+        unsigned long flags;
         int error = -ESRCH;
 
-        read_lock(&tasklist_lock);
-        if (likely(child->sighand != NULL)) {
+        if (lock_task_sighand(child, &flags)) {
                 error = -EINVAL;
-                spin_lock_irq(&child->sighand->siglock);
                 if (likely(child->last_siginfo != NULL)) {
                         *child->last_siginfo = *info;
                         error = 0;
                 }
-                spin_unlock_irq(&child->sighand->siglock);
+                unlock_task_sighand(child, &flags);
         }
-        read_unlock(&tasklist_lock);
         return error;
 }
 
@@ -566,72 +577,16 @@ int ptrace_request(struct task_struct *child, long request,
         return ret;
 }
 
-/**
- * ptrace_traceme  --  helper for PTRACE_TRACEME
- *
- * Performs checks and sets PT_PTRACED.
- * Should be used by all ptrace implementations for PTRACE_TRACEME.
- */
-int ptrace_traceme(void)
-{
-        int ret = -EPERM;
-
-        /*
-         * Are we already being traced?
-         */
-repeat:
-        task_lock(current);
-        if (!(current->ptrace & PT_PTRACED)) {
-                /*
-                 * See ptrace_attach() comments about the locking here.
-                 */
-                unsigned long flags;
-                if (!write_trylock_irqsave(&tasklist_lock, flags)) {
-                        task_unlock(current);
-                        do {
-                                cpu_relax();
-                        } while (!write_can_lock(&tasklist_lock));
-                        goto repeat;
-                }
-
-                ret = security_ptrace_traceme(current->parent);
-
-                /*
-                 * Check PF_EXITING to ensure ->real_parent has not passed
-                 * exit_ptrace(). Otherwise we don't report the error but
-                 * pretend ->real_parent untraces us right after return.
-                 */
-                if (!ret && !(current->real_parent->flags & PF_EXITING)) {
-                        current->ptrace |= PT_PTRACED;
-                        __ptrace_link(current, current->real_parent);
-                }
-
-                write_unlock_irqrestore(&tasklist_lock, flags);
-        }
-        task_unlock(current);
-        return ret;
-}
-
-/**
- * ptrace_get_task_struct  --  grab a task struct reference for ptrace
- * @pid:       process id to grab a task_struct reference of
- *
- * This function is a helper for ptrace implementations.  It checks
- * permissions and then grabs a task struct for use of the actual
- * ptrace implementation.
- *
- * Returns the task_struct for @pid or an ERR_PTR() on failure.
- */
-struct task_struct *ptrace_get_task_struct(pid_t pid)
+static struct task_struct *ptrace_get_task_struct(pid_t pid)
 {
         struct task_struct *child;
 
-        read_lock(&tasklist_lock);
+        rcu_read_lock();
         child = find_task_by_vpid(pid);
         if (child)
                 get_task_struct(child);
+        rcu_read_unlock();
 
-        read_unlock(&tasklist_lock);
         if (!child)
                 return ERR_PTR(-ESRCH);
         return child;