Commit 66dcca06 authored by Sripathi Kodi's avatar Sripathi Kodi Committed by Linus Torvalds
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[PATCH] Fix invisible threads problem 



When the main thread of a thread group has done pthread_exit() and died,
the other threads are still happily running, but will not be visible
under /proc because their leader is no longer accessible.

This fixes the access control so that we can see the sub-threads again.

Signed-off-by: default avatarSripathi Kodi <sripathik@in.ibm.com>
Acked-by: default avatarAl Viro <viro@ftp.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d79e743e

fs/proc/base.c

+77 −7
Original line number Diff line number Diff line
@@ -340,6 +340,52 @@ static int proc_root_link(struct inode *inode, struct dentry **dentry, struct vf 
	return result;

}





/* Same as proc_root_link, but this addionally tries to get fs from other

 * threads in the group */

static int proc_task_root_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)

{

	struct fs_struct *fs;

	int result = -ENOENT;

	struct task_struct *leader = proc_task(inode);



	task_lock(leader);

	fs = leader->fs;

	if (fs) {

		atomic_inc(&fs->count);

		task_unlock(leader);

	} else {

		/* Try to get fs from other threads */

		task_unlock(leader);

		struct task_struct *task = leader;

		read_lock(&tasklist_lock);

		if (pid_alive(task)) {

			while ((task = next_thread(task)) != leader) {

				task_lock(task);

				fs = task->fs;

				if (fs) {

					atomic_inc(&fs->count);

					task_unlock(task);

					break;

				}

				task_unlock(task);

			}

		}

		read_unlock(&tasklist_lock);

	}



	if (fs) {

		read_lock(&fs->lock);

		*mnt = mntget(fs->rootmnt);

		*dentry = dget(fs->root);

		read_unlock(&fs->lock);

		result = 0;

		put_fs_struct(fs);

	}

	return result;

}





#define MAY_PTRACE(task) \

	(task == current || \

	(task->parent == current && \
@@ -471,14 +517,14 @@ static int proc_oom_score(struct task_struct *task, char *buffer) 


/* permission checks */



static int proc_check_root(struct inode *inode)

/* If the process being read is separated by chroot from the reading process,

 * don't let the reader access the threads.

 */

static int proc_check_chroot(struct dentry *root, struct vfsmount *vfsmnt)

{

	struct dentry *de, *base, *root;

	struct vfsmount *our_vfsmnt, *vfsmnt, *mnt;

	struct dentry *de, *base;

	struct vfsmount *our_vfsmnt, *mnt;

	int res = 0;



	if (proc_root_link(inode, &root, &vfsmnt)) /* Ewww... */

		return -ENOENT;

	read_lock(&current->fs->lock);

	our_vfsmnt = mntget(current->fs->rootmnt);

	base = dget(current->fs->root);
@@ -511,6 +557,16 @@ out: 
	goto exit;

}



static int proc_check_root(struct inode *inode)

{

	struct dentry *root;

	struct vfsmount *vfsmnt;



	if (proc_root_link(inode, &root, &vfsmnt)) /* Ewww... */

		return -ENOENT;

	return proc_check_chroot(root, vfsmnt);

}



static int proc_permission(struct inode *inode, int mask, struct nameidata *nd)

{

	if (generic_permission(inode, mask, NULL) != 0)
@@ -518,6 +574,20 @@ static int proc_permission(struct inode *inode, int mask, struct nameidata *nd) 
	return proc_check_root(inode);

}



static int proc_task_permission(struct inode *inode, int mask, struct nameidata *nd)

{

	struct dentry *root;

	struct vfsmount *vfsmnt;



	if (generic_permission(inode, mask, NULL) != 0)

		return -EACCES;



	if (proc_task_root_link(inode, &root, &vfsmnt))

		return -ENOENT;



	return proc_check_chroot(root, vfsmnt);

}



extern struct seq_operations proc_pid_maps_op;

static int maps_open(struct inode *inode, struct file *file)

{
@@ -1419,7 +1489,7 @@ static struct inode_operations proc_fd_inode_operations = { 


static struct inode_operations proc_task_inode_operations = {

	.lookup		= proc_task_lookup,

	.permission	= proc_permission,

	.permission	= proc_task_permission,

};



#ifdef CONFIG_SECURITY

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