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Commit 68eb94f1 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

proc: Better ownership of files for non-dumpable tasks in user namespaces 



Instead of making the files owned by the GLOBAL_ROOT_USER.  Make
non-dumpable files whose mm has always lived in a user namespace owned
by the user namespace root.  This allows the container root to have
things work as expected in a container.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 9227dd2a

fs/proc/base.c

+58 −44
Original line number Diff line number Diff line
@@ -1667,12 +1667,63 @@ const struct inode_operations proc_pid_link_inode_operations = { 


/* building an inode */



void task_dump_owner(struct task_struct *task, mode_t mode,

		     kuid_t *ruid, kgid_t *rgid)

{

	/* Depending on the state of dumpable compute who should own a

	 * proc file for a task.

	 */

	const struct cred *cred;

	kuid_t uid;

	kgid_t gid;



	/* Default to the tasks effective ownership */

	rcu_read_lock();

	cred = __task_cred(task);

	uid = cred->euid;

	gid = cred->egid;

	rcu_read_unlock();



	/*

	 * Before the /proc/pid/status file was created the only way to read

	 * the effective uid of a /process was to stat /proc/pid.  Reading

	 * /proc/pid/status is slow enough that procps and other packages

	 * kept stating /proc/pid.  To keep the rules in /proc simple I have

	 * made this apply to all per process world readable and executable

	 * directories.

	 */

	if (mode != (S_IFDIR|S_IRUGO|S_IXUGO)) {

		struct mm_struct *mm;

		task_lock(task);

		mm = task->mm;

		/* Make non-dumpable tasks owned by some root */

		if (mm) {

			if (get_dumpable(mm) != SUID_DUMP_USER) {

				struct user_namespace *user_ns = mm->user_ns;



				uid = make_kuid(user_ns, 0);

				if (!uid_valid(uid))

					uid = GLOBAL_ROOT_UID;



				gid = make_kgid(user_ns, 0);

				if (!gid_valid(gid))

					gid = GLOBAL_ROOT_GID;

			}

		} else {

			uid = GLOBAL_ROOT_UID;

			gid = GLOBAL_ROOT_GID;

		}

		task_unlock(task);

	}

	*ruid = uid;

	*rgid = gid;

}



struct inode *proc_pid_make_inode(struct super_block * sb,

				  struct task_struct *task, umode_t mode)

{

	struct inode * inode;

	struct proc_inode *ei;

	const struct cred *cred;



	/* We need a new inode */
@@ -1694,13 +1745,7 @@ struct inode *proc_pid_make_inode(struct super_block * sb, 
	if (!ei->pid)

		goto out_unlock;



	if (task_dumpable(task)) {

		rcu_read_lock();

		cred = __task_cred(task);

		inode->i_uid = cred->euid;

		inode->i_gid = cred->egid;

		rcu_read_unlock();

	}

	task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);

	security_task_to_inode(task, inode);



out:
@@ -1715,7 +1760,6 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) 
{

	struct inode *inode = d_inode(dentry);

	struct task_struct *task;

	const struct cred *cred;

	struct pid_namespace *pid = dentry->d_sb->s_fs_info;



	generic_fillattr(inode, stat);
@@ -1733,12 +1777,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) 
			 */

			return -ENOENT;

		}

		if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||

		    task_dumpable(task)) {

			cred = __task_cred(task);

			stat->uid = cred->euid;

			stat->gid = cred->egid;

		}

		task_dump_owner(task, inode->i_mode, &stat->uid, &stat->gid);

	}

	rcu_read_unlock();

	return 0;
@@ -1754,18 +1793,11 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) 
 * Rewrite the inode's ownerships here because the owning task may have

 * performed a setuid(), etc.

 *

 * Before the /proc/pid/status file was created the only way to read

 * the effective uid of a /process was to stat /proc/pid.  Reading

 * /proc/pid/status is slow enough that procps and other packages

 * kept stating /proc/pid.  To keep the rules in /proc simple I have

 * made this apply to all per process world readable and executable

 * directories.

 */

int pid_revalidate(struct dentry *dentry, unsigned int flags)

{

	struct inode *inode;

	struct task_struct *task;

	const struct cred *cred;



	if (flags & LOOKUP_RCU)

		return -ECHILD;
@@ -1774,17 +1806,8 @@ int pid_revalidate(struct dentry *dentry, unsigned int flags) 
	task = get_proc_task(inode);



	if (task) {

		if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||

		    task_dumpable(task)) {

			rcu_read_lock();

			cred = __task_cred(task);

			inode->i_uid = cred->euid;

			inode->i_gid = cred->egid;

			rcu_read_unlock();

		} else {

			inode->i_uid = GLOBAL_ROOT_UID;

			inode->i_gid = GLOBAL_ROOT_GID;

		}

		task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);



		inode->i_mode &= ~(S_ISUID | S_ISGID);

		security_task_to_inode(task, inode);

		put_task_struct(task);
@@ -1881,7 +1904,6 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags) 
	bool exact_vma_exists = false;

	struct mm_struct *mm = NULL;

	struct task_struct *task;

	const struct cred *cred;

	struct inode *inode;

	int status = 0;
@@ -1906,16 +1928,8 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags) 
	mmput(mm);



	if (exact_vma_exists) {

		if (task_dumpable(task)) {

			rcu_read_lock();

			cred = __task_cred(task);

			inode->i_uid = cred->euid;

			inode->i_gid = cred->egid;

			rcu_read_unlock();

		} else {

			inode->i_uid = GLOBAL_ROOT_UID;

			inode->i_gid = GLOBAL_ROOT_GID;

		}

		task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);



		security_task_to_inode(task, inode);

		status = 1;

	}

fs/proc/fd.c

+1 −11
Original line number Diff line number Diff line
@@ -84,7 +84,6 @@ static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags) 
{

	struct files_struct *files;

	struct task_struct *task;

	const struct cred *cred;

	struct inode *inode;

	unsigned int fd;
@@ -108,16 +107,7 @@ static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags) 
				rcu_read_unlock();

				put_files_struct(files);



				if (task_dumpable(task)) {

					rcu_read_lock();

					cred = __task_cred(task);

					inode->i_uid = cred->euid;

					inode->i_gid = cred->egid;

					rcu_read_unlock();

				} else {

					inode->i_uid = GLOBAL_ROOT_UID;

					inode->i_gid = GLOBAL_ROOT_GID;

				}

				task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);



				if (S_ISLNK(inode->i_mode)) {

					unsigned i_mode = S_IFLNK;

fs/proc/internal.h

+2 −14
Original line number Diff line number Diff line
@@ -97,20 +97,8 @@ static inline struct task_struct *get_proc_task(struct inode *inode) 
	return get_pid_task(proc_pid(inode), PIDTYPE_PID);

}



static inline int task_dumpable(struct task_struct *task)

{

	int dumpable = 0;

	struct mm_struct *mm;



	task_lock(task);

	mm = task->mm;

	if (mm)

		dumpable = get_dumpable(mm);

	task_unlock(task);

	if (dumpable == SUID_DUMP_USER)

		return 1;

	return 0;

}

void task_dump_owner(struct task_struct *task, mode_t mode,

		     kuid_t *ruid, kgid_t *rgid);



static inline unsigned name_to_int(const struct qstr *qstr)

{