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proc: Better ownership of files for non-dumpable tasks in user namesp…
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…aces

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: "Eric W. Biederman" <[email protected]>
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@ebiederm
ebiederm committed Jan 23, 2017
1 parent 9227dd2 commit 68eb94f
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Showing 3 changed files with 61 additions and 69 deletions.
102 changes: 58 additions & 44 deletions fs/proc/base.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */

Expand All @@ -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:
Expand All @@ -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);
Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -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);
Expand Down Expand Up @@ -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;

Expand All @@ -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;
}
Expand Down
12 changes: 1 addition & 11 deletions fs/proc/fd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand All @@ -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;
Expand Down
16 changes: 2 additions & 14 deletions fs/proc/internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down

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