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
......@@ -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 @@ static int proc_check_root(struct inode *inode)
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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