proc: don't (ab)use ->group_leader in proc_task_readdir() paths

[platform/adaptation/renesas_rcar/renesas_kernel.git] / fs / proc / base.c

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 03c8d74..9b423fe 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1658,13 +1658,18 @@ int pid_revalidate(struct dentry *dentry, unsigned int flags)
        return 0;
 }
 
+static inline bool proc_inode_is_dead(struct inode *inode)
+{
+       return !proc_pid(inode)->tasks[PIDTYPE_PID].first;
+}
+
 int pid_delete_dentry(const struct dentry *dentry)
 {
        /* Is the task we represent dead?
         * If so, then don't put the dentry on the lru list,
         * kill it immediately.
         */
-       return !proc_pid(dentry->d_inode)->tasks[PIDTYPE_PID].first;
+       return proc_inode_is_dead(dentry->d_inode);
 }
 
 const struct dentry_operations pid_dentry_operations =
@@ -3092,34 +3097,38 @@ out_no_task:
  * In the case of a seek we start with the leader and walk nr
  * threads past it.
  */
-static struct task_struct *first_tid(struct task_struct *leader,
-               int tid, int nr, struct pid_namespace *ns)
+static struct task_struct *first_tid(struct pid *pid, int tid,
+                                       int nr, struct pid_namespace *ns)
 {
-       struct task_struct *pos;
+       struct task_struct *pos, *task;
 
        rcu_read_lock();
-       /* Attempt to start with the pid of a thread */
+       task = pid_task(pid, PIDTYPE_PID);
+       if (!task)
+               goto fail;
+
+       /* Attempt to start with the tid of a thread */
        if (tid && (nr > 0)) {
                pos = find_task_by_pid_ns(tid, ns);
-               if (pos && (pos->group_leader == leader))
+               if (pos && same_thread_group(pos, task))
                        goto found;
        }
 
        /* If nr exceeds the number of threads there is nothing todo */
-       pos = NULL;
-       if (nr && nr >= get_nr_threads(leader))
-               goto out;
+       if (nr && nr >= get_nr_threads(task))
+               goto fail;
 
        /* If we haven't found our starting place yet start
         * with the leader and walk nr threads forward.
         */
-       for (pos = leader; nr > 0; --nr) {
-               pos = next_thread(pos);
-               if (pos == leader) {
-                       pos = NULL;
-                       goto out;
-               }
-       }
+       pos = task = task->group_leader;
+       do {
+               if (nr-- <= 0)
+                       goto found;
+       } while_each_thread(task, pos);
+fail:
+       pos = NULL;
+       goto out;
 found:
        get_task_struct(pos);
 out:
@@ -3152,25 +3161,16 @@ static struct task_struct *next_tid(struct task_struct *start)
 /* for the /proc/TGID/task/ directories */
 static int proc_task_readdir(struct file *file, struct dir_context *ctx)
 {
-       struct task_struct *leader = NULL;
-       struct task_struct *task = get_proc_task(file_inode(file));
+       struct inode *inode = file_inode(file);
+       struct task_struct *task;
        struct pid_namespace *ns;
        int tid;
 
-       if (!task)
-               return -ENOENT;
-       rcu_read_lock();
-       if (pid_alive(task)) {
-               leader = task->group_leader;
-               get_task_struct(leader);
-       }
-       rcu_read_unlock();
-       put_task_struct(task);
-       if (!leader)
+       if (proc_inode_is_dead(inode))
                return -ENOENT;
 
        if (!dir_emit_dots(file, ctx))
-               goto out;
+               return 0;
 
        /* f_version caches the tgid value that the last readdir call couldn't
         * return. lseek aka telldir automagically resets f_version to 0.
@@ -3178,7 +3178,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
        ns = file->f_dentry->d_sb->s_fs_info;
        tid = (int)file->f_version;
        file->f_version = 0;
-       for (task = first_tid(leader, tid, ctx->pos - 2, ns);
+       for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
             task;
             task = next_tid(task), ctx->pos++) {
                char name[PROC_NUMBUF];
@@ -3194,8 +3194,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
                        break;
                }
        }
-out:
-       put_task_struct(leader);
+
        return 0;
 }