linux/fs/proc/fd.c
Christian Brauner 549c729771
fs: make helpers idmap mount aware
Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.

As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.

Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2021-01-24 14:27:20 +01:00

347 lines
7.5 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/sched/signal.h>
#include <linux/errno.h>
#include <linux/dcache.h>
#include <linux/path.h>
#include <linux/fdtable.h>
#include <linux/namei.h>
#include <linux/pid.h>
#include <linux/security.h>
#include <linux/file.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include "../mount.h"
#include "internal.h"
#include "fd.h"
static int seq_show(struct seq_file *m, void *v)
{
struct files_struct *files = NULL;
int f_flags = 0, ret = -ENOENT;
struct file *file = NULL;
struct task_struct *task;
task = get_proc_task(m->private);
if (!task)
return -ENOENT;
task_lock(task);
files = task->files;
if (files) {
unsigned int fd = proc_fd(m->private);
spin_lock(&files->file_lock);
file = files_lookup_fd_locked(files, fd);
if (file) {
struct fdtable *fdt = files_fdtable(files);
f_flags = file->f_flags;
if (close_on_exec(fd, fdt))
f_flags |= O_CLOEXEC;
get_file(file);
ret = 0;
}
spin_unlock(&files->file_lock);
}
task_unlock(task);
put_task_struct(task);
if (ret)
return ret;
seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
(long long)file->f_pos, f_flags,
real_mount(file->f_path.mnt)->mnt_id);
/* show_fd_locks() never deferences files so a stale value is safe */
show_fd_locks(m, file, files);
if (seq_has_overflowed(m))
goto out;
if (file->f_op->show_fdinfo)
file->f_op->show_fdinfo(m, file);
out:
fput(file);
return 0;
}
static int seq_fdinfo_open(struct inode *inode, struct file *file)
{
return single_open(file, seq_show, inode);
}
static const struct file_operations proc_fdinfo_file_operations = {
.open = seq_fdinfo_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
{
struct file *file;
rcu_read_lock();
file = task_lookup_fd_rcu(task, fd);
if (file)
*mode = file->f_mode;
rcu_read_unlock();
return !!file;
}
static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
fmode_t f_mode)
{
task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
if (S_ISLNK(inode->i_mode)) {
unsigned i_mode = S_IFLNK;
if (f_mode & FMODE_READ)
i_mode |= S_IRUSR | S_IXUSR;
if (f_mode & FMODE_WRITE)
i_mode |= S_IWUSR | S_IXUSR;
inode->i_mode = i_mode;
}
security_task_to_inode(task, inode);
}
static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
{
struct task_struct *task;
struct inode *inode;
unsigned int fd;
if (flags & LOOKUP_RCU)
return -ECHILD;
inode = d_inode(dentry);
task = get_proc_task(inode);
fd = proc_fd(inode);
if (task) {
fmode_t f_mode;
if (tid_fd_mode(task, fd, &f_mode)) {
tid_fd_update_inode(task, inode, f_mode);
put_task_struct(task);
return 1;
}
put_task_struct(task);
}
return 0;
}
static const struct dentry_operations tid_fd_dentry_operations = {
.d_revalidate = tid_fd_revalidate,
.d_delete = pid_delete_dentry,
};
static int proc_fd_link(struct dentry *dentry, struct path *path)
{
struct task_struct *task;
int ret = -ENOENT;
task = get_proc_task(d_inode(dentry));
if (task) {
unsigned int fd = proc_fd(d_inode(dentry));
struct file *fd_file;
fd_file = fget_task(task, fd);
if (fd_file) {
*path = fd_file->f_path;
path_get(&fd_file->f_path);
ret = 0;
fput(fd_file);
}
put_task_struct(task);
}
return ret;
}
struct fd_data {
fmode_t mode;
unsigned fd;
};
static struct dentry *proc_fd_instantiate(struct dentry *dentry,
struct task_struct *task, const void *ptr)
{
const struct fd_data *data = ptr;
struct proc_inode *ei;
struct inode *inode;
inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
if (!inode)
return ERR_PTR(-ENOENT);
ei = PROC_I(inode);
ei->fd = data->fd;
inode->i_op = &proc_pid_link_inode_operations;
inode->i_size = 64;
ei->op.proc_get_link = proc_fd_link;
tid_fd_update_inode(task, inode, data->mode);
d_set_d_op(dentry, &tid_fd_dentry_operations);
return d_splice_alias(inode, dentry);
}
static struct dentry *proc_lookupfd_common(struct inode *dir,
struct dentry *dentry,
instantiate_t instantiate)
{
struct task_struct *task = get_proc_task(dir);
struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
struct dentry *result = ERR_PTR(-ENOENT);
if (!task)
goto out_no_task;
if (data.fd == ~0U)
goto out;
if (!tid_fd_mode(task, data.fd, &data.mode))
goto out;
result = instantiate(dentry, task, &data);
out:
put_task_struct(task);
out_no_task:
return result;
}
static int proc_readfd_common(struct file *file, struct dir_context *ctx,
instantiate_t instantiate)
{
struct task_struct *p = get_proc_task(file_inode(file));
unsigned int fd;
if (!p)
return -ENOENT;
if (!dir_emit_dots(file, ctx))
goto out;
rcu_read_lock();
for (fd = ctx->pos - 2;; fd++) {
struct file *f;
struct fd_data data;
char name[10 + 1];
unsigned int len;
f = task_lookup_next_fd_rcu(p, &fd);
ctx->pos = fd + 2LL;
if (!f)
break;
data.mode = f->f_mode;
rcu_read_unlock();
data.fd = fd;
len = snprintf(name, sizeof(name), "%u", fd);
if (!proc_fill_cache(file, ctx,
name, len, instantiate, p,
&data))
goto out;
cond_resched();
rcu_read_lock();
}
rcu_read_unlock();
out:
put_task_struct(p);
return 0;
}
static int proc_readfd(struct file *file, struct dir_context *ctx)
{
return proc_readfd_common(file, ctx, proc_fd_instantiate);
}
const struct file_operations proc_fd_operations = {
.read = generic_read_dir,
.iterate_shared = proc_readfd,
.llseek = generic_file_llseek,
};
static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
}
/*
* /proc/pid/fd needs a special permission handler so that a process can still
* access /proc/self/fd after it has executed a setuid().
*/
int proc_fd_permission(struct user_namespace *mnt_userns,
struct inode *inode, int mask)
{
struct task_struct *p;
int rv;
rv = generic_permission(&init_user_ns, inode, mask);
if (rv == 0)
return rv;
rcu_read_lock();
p = pid_task(proc_pid(inode), PIDTYPE_PID);
if (p && same_thread_group(p, current))
rv = 0;
rcu_read_unlock();
return rv;
}
const struct inode_operations proc_fd_inode_operations = {
.lookup = proc_lookupfd,
.permission = proc_fd_permission,
.setattr = proc_setattr,
};
static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
struct task_struct *task, const void *ptr)
{
const struct fd_data *data = ptr;
struct proc_inode *ei;
struct inode *inode;
inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUSR);
if (!inode)
return ERR_PTR(-ENOENT);
ei = PROC_I(inode);
ei->fd = data->fd;
inode->i_fop = &proc_fdinfo_file_operations;
tid_fd_update_inode(task, inode, 0);
d_set_d_op(dentry, &tid_fd_dentry_operations);
return d_splice_alias(inode, dentry);
}
static struct dentry *
proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
}
static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
{
return proc_readfd_common(file, ctx,
proc_fdinfo_instantiate);
}
const struct inode_operations proc_fdinfo_inode_operations = {
.lookup = proc_lookupfdinfo,
.setattr = proc_setattr,
};
const struct file_operations proc_fdinfo_operations = {
.read = generic_read_dir,
.iterate_shared = proc_readfdinfo,
.llseek = generic_file_llseek,
};