[PATCH] procfs: Fix listing of /proc/NOT_A_TGID/task

Listing /proc/PID/task were PID is not a TGID should not result in
duplicated entries.

	[g ~]$ pidof thunderbird-bin
	2751
	[g ~]$ ls /proc/2751/task
	2751  2770  2771  2824  2826  2834  2835  2851  2853
	[g ~]$ ls /proc/2770/task
	2751  2770  2771  2824  2826  2834  2835  2851  2853
	2770  2771  2824  2826  2834  2835  2851  2853
	[g ~]$

Signed-off-by: Guillaume Chazarain <guichaz@yahoo.fr>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ff7a66850602cb4fced3a5250d74bd43d42d4d8b..1a979ea3b379931973f79c4b70703df3f237c714 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2328,13 +2328,23 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
 {
        struct dentry *dentry = filp->f_path.dentry;
        struct inode *inode = dentry->d_inode;
-       struct task_struct *leader = get_proc_task(inode);
+       struct task_struct *leader = NULL;
        struct task_struct *task;
        int retval = -ENOENT;
        ino_t ino;
        int tid;
        unsigned long pos = filp->f_pos;  /* avoiding "long long" filp->f_pos */
 
+       task = get_proc_task(inode);
+       if (!task)
+               goto out_no_task;
+       rcu_read_lock();
+       if (pid_alive(task)) {
+               leader = task->group_leader;
+               get_task_struct(leader);
+       }
+       rcu_read_unlock();
+       put_task_struct(task);
        if (!leader)
                goto out_no_task;
        retval = 0;