1 files changed, 163 insertions, 140 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index c9cf48b21f05..23bd09cd042e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -21,22 +21,10 @@
 #include <linux/audit.h>
 #include <linux/pid_namespace.h>
 #include <linux/syscalls.h>
-
-#include <asm/pgtable.h>
-#include <asm/uaccess.h>
+#include <linux/uaccess.h>
 
 
 /*
- * Initialize a new task whose father had been ptraced.
- *
- * Called from copy_process().
- */
-void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
-{
-        arch_ptrace_fork(child, clone_flags);
-}
-
-/*
  * ptrace a task: make the debugger its new parent and
  * move it to the ptrace list.
  *
@@ -48,7 +36,7 @@ void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
         list_add(&child->ptrace_entry, &new_parent->ptraced);
         child->parent = new_parent;
 }
- 
+
 /*
  * Turn a tracing stop into a normal stop now, since with no tracer there
  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
@@ -60,11 +48,15 @@ static void ptrace_untrace(struct task_struct *child)
 {
         spin_lock(&child->sighand->siglock);
         if (task_is_traced(child)) {
-                if (child->signal->flags & SIGNAL_STOP_STOPPED) {
+                /*
+                 * If the group stop is completed or in progress,
+                 * this thread was already counted as stopped.
+                 */
+                if (child->signal->flags & SIGNAL_STOP_STOPPED ||
+                    child->signal->group_stop_count)
                         __set_task_state(child, TASK_STOPPED);
-                } else {
+                else
                         signal_wake_up(child, 1);
-                }
         }
         spin_unlock(&child->sighand->siglock);
 }
@@ -160,7 +152,7 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
         if (!dumpable && !capable(CAP_SYS_PTRACE))
                 return -EPERM;
 
-        return security_ptrace_may_access(task, mode);
+        return security_ptrace_access_check(task, mode);
 }
 
 bool ptrace_may_access(struct task_struct *task, unsigned int mode)
@@ -169,84 +161,143 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode)
         task_lock(task);
         err = __ptrace_may_access(task, mode);
         task_unlock(task);
-        return (!err ? true : false);
+        return !err;
 }
 
 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 exec's credential calculations against our interference;
-         * SUID, SGID and LSM creds get determined differently under ptrace.
+        /*
+         * Protect exec's credential calculations against our interference;
+         * interference; SUID, SGID and LSM creds get determined differently
+         * under ptrace.
          */
-        retval = mutex_lock_interruptible(&current->cred_exec_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);
-        mutex_unlock(&current->cred_exec_mutex);
+
+        retval = 0;
+unlock_tasklist:
+        write_unlock_irq(&tasklist_lock);
+unlock_creds:
+        mutex_unlock(&task->cred_guard_mutex);
 out:
         return retval;
 }
 
-static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
+/**
+ * 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)
 {
-        child->exit_code = data;
-        /* .. re-parent .. */
-        __ptrace_unlink(child);
-        /* .. and wake it up. */
-        if (child->exit_state != EXIT_ZOMBIE)
-                wake_up_process(child);
+        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.
+ */
+static int ignoring_children(struct sighand_struct *sigh)
+{
+        int ret;
+        spin_lock(&sigh->siglock);
+        ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
+              (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
+        spin_unlock(&sigh->siglock);
+        return ret;
+}
+
+/*
+ * Called with tasklist_lock held for writing.
+ * Unlink a traced task, and clean it up if it was a traced zombie.
+ * Return true if it needs to be reaped with release_task().
+ * (We can't call release_task() here because we already hold tasklist_lock.)
+ *
+ * If it's a zombie, our attachedness prevented normal parent notification
+ * or self-reaping.  Do notification now if it would have happened earlier.
+ * If it should reap itself, return true.
+ *
+ * If it's our own child, there is no notification to do. But if our normal
+ * children self-reap, then this child was prevented by ptrace and we must
+ * reap it now, in that case we must also wake up sub-threads sleeping in
+ * do_wait().
+ */
+static bool __ptrace_detach(struct task_struct *tracer, struct task_struct *p)
+{
+        __ptrace_unlink(p);
+
+        if (p->exit_state == EXIT_ZOMBIE) {
+                if (!task_detached(p) && thread_group_empty(p)) {
+                        if (!same_thread_group(p->real_parent, tracer))
+                                do_notify_parent(p, p->exit_signal);
+                        else if (ignoring_children(tracer->sighand)) {
+                                __wake_up_parent(p, tracer);
+                                p->exit_signal = -1;
+                        }
+                }
+                if (task_detached(p)) {
+                        /* Mark it as in the process of being reaped. */
+                        p->exit_state = EXIT_DEAD;
+                        return true;
+                }
+        }
+
+        return false;
 }
 
 int ptrace_detach(struct task_struct *child, unsigned int data)
 {
+        bool dead = false;
+
         if (!valid_signal(data))
                 return -EIO;
 
@@ -255,14 +306,47 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 
         write_lock_irq(&tasklist_lock);
-        /* protect against de_thread()->release_task() */
-        if (child->ptrace)
-                __ptrace_detach(child, data);
+        /*
+         * This child can be already killed. Make sure de_thread() or
+         * our sub-thread doing do_wait() didn't do release_task() yet.
+         */
+        if (child->ptrace) {
+                child->exit_code = data;
+                dead = __ptrace_detach(current, child);
+                if (!child->exit_state)
+                        wake_up_process(child);
+        }
         write_unlock_irq(&tasklist_lock);
 
+        if (unlikely(dead))
+                release_task(child);
+
         return 0;
 }
 
+/*
+ * Detach all tasks we were using ptrace on.
+ */
+void exit_ptrace(struct task_struct *tracer)
+{
+        struct task_struct *p, *n;
+        LIST_HEAD(ptrace_dead);
+
+        write_lock_irq(&tasklist_lock);
+        list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
+                if (__ptrace_detach(tracer, p))
+                        list_add(&p->ptrace_entry, &ptrace_dead);
+        }
+        write_unlock_irq(&tasklist_lock);
+
+        BUG_ON(!list_empty(&tracer->ptraced));
+
+        list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
+                list_del_init(&p->ptrace_entry);
+                release_task(p);
+        }
+}
+
 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 {
         int copied = 0;
@@ -283,7 +367,7 @@ int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst
                 copied += retval;
                 src += retval;
                 dst += retval;
-                len -= retval;                  
+                len -= retval;
         }
         return copied;
 }
@@ -308,7 +392,7 @@ int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long ds
                 copied += retval;
                 src += retval;
                 dst += retval;
-                len -= retval;                  
+                len -= retval;
         }
         return copied;
 }
@@ -343,37 +427,33 @@ 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;
 }
 
@@ -421,9 +501,9 @@ static int ptrace_resume(struct task_struct *child, long request, long data)
                 if (unlikely(!arch_has_single_step()))
                         return -EIO;
                 user_enable_single_step(child);
-        }
-        else
+        } else {
                 user_disable_single_step(child);
+        }
 
         child->exit_code = data;
         wake_up_process(child);
@@ -500,71 +580,16 @@ 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);
-
-                /*
-                 * Set the ptrace bit in the process ptrace flags.
-                 * Then link us on our parent's ptraced list.
-                 */
-                if (!ret) {
-                        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;
@@ -612,8 +637,6 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
                 goto out_put_task_struct;
 
         ret = arch_ptrace(child, request, addr, data);
-        if (ret < 0)
-                goto out_put_task_struct;
 
  out_put_task_struct:
         put_task_struct(child);