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cgroup: restructure cgroup_procs_write_permission()

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Restructure cgroup_procs_write_permission() to make extending
permission logic easier.

This patch doesn't cause any functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2017-06-25 00:27:59 -04:00
parent 39fd64ae9f
commit 824ecbe01c
1 changed files with 33 additions and 24 deletions
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51
kernel/cgroup/cgroup.c
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@ -2363,27 +2363,12 @@ static int cgroup_procs_write_permission(struct task_struct *task,
struct cgroup *dst_cgrp,
struct kernfs_open_file *of)
{
int ret = 0;
if (cgroup_on_dfl(dst_cgrp)) {
struct super_block *sb = of->file->f_path.dentry->d_sb;
struct cgroup *cgrp;
struct cgroup *src_cgrp, *com_cgrp;
struct inode *inode;
int ret;
spin_lock_irq(&css_set_lock);
cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
spin_unlock_irq(&css_set_lock);
while (!cgroup_is_descendant(dst_cgrp, cgrp))
cgrp = cgroup_parent(cgrp);
ret = -ENOMEM;
inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
if (inode) {
ret = inode_permission(inode, MAY_WRITE);
iput(inode);
}
} else {
if (!cgroup_on_dfl(dst_cgrp)) {
const struct cred *cred = current_cred();
const struct cred *tcred = get_task_cred(task);
@ -2391,14 +2376,38 @@ static int cgroup_procs_write_permission(struct task_struct *task,
* even if we're attaching all tasks in the thread group,
* we only need to check permissions on one of them.
*/
if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
!uid_eq(cred->euid, tcred->uid) &&
!uid_eq(cred->euid, tcred->suid))
if (uid_eq(cred->euid, GLOBAL_ROOT_UID) ||
uid_eq(cred->euid, tcred->uid) ||
uid_eq(cred->euid, tcred->suid))
ret = 0;
else
ret = -EACCES;
put_cred(tcred);
return ret;
}
/* find the source cgroup */
spin_lock_irq(&css_set_lock);
src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
spin_unlock_irq(&css_set_lock);
/* and the common ancestor */
com_cgrp = src_cgrp;
while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
com_cgrp = cgroup_parent(com_cgrp);
/* %current should be authorized to migrate to the common ancestor */
inode = kernfs_get_inode(sb, com_cgrp->procs_file.kn);
if (!inode)
return -ENOMEM;
ret = inode_permission(inode, MAY_WRITE);
iput(inode);
if (ret)
return ret;
return 0;
}
/*