linux/fs/overlayfs/file.c
Amir Goldstein f567377e40 fs: factor out backing_file_mmap() helper
Assert that the file object is allocated in a backing_file container
so that file_user_path() could be used to display the user path and
not the backing file's path in /proc/<pid>/maps.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
2023-12-23 16:35:09 +02:00

616 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017 Red Hat, Inc.
*/
#include <linux/cred.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/xattr.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
#include <linux/security.h>
#include <linux/fs.h>
#include <linux/backing-file.h>
#include "overlayfs.h"
static char ovl_whatisit(struct inode *inode, struct inode *realinode)
{
if (realinode != ovl_inode_upper(inode))
return 'l';
if (ovl_has_upperdata(inode))
return 'u';
else
return 'm';
}
/* No atime modification on underlying */
#define OVL_OPEN_FLAGS (O_NOATIME)
static struct file *ovl_open_realfile(const struct file *file,
const struct path *realpath)
{
struct inode *realinode = d_inode(realpath->dentry);
struct inode *inode = file_inode(file);
struct mnt_idmap *real_idmap;
struct file *realfile;
const struct cred *old_cred;
int flags = file->f_flags | OVL_OPEN_FLAGS;
int acc_mode = ACC_MODE(flags);
int err;
if (flags & O_APPEND)
acc_mode |= MAY_APPEND;
old_cred = ovl_override_creds(inode->i_sb);
real_idmap = mnt_idmap(realpath->mnt);
err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
if (err) {
realfile = ERR_PTR(err);
} else {
if (!inode_owner_or_capable(real_idmap, realinode))
flags &= ~O_NOATIME;
realfile = backing_file_open(&file->f_path, flags, realpath,
current_cred());
}
revert_creds(old_cred);
pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
file, file, ovl_whatisit(inode, realinode), file->f_flags,
realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
return realfile;
}
#define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
static int ovl_change_flags(struct file *file, unsigned int flags)
{
struct inode *inode = file_inode(file);
int err;
flags &= OVL_SETFL_MASK;
if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
return -EPERM;
if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))
return -EINVAL;
if (file->f_op->check_flags) {
err = file->f_op->check_flags(flags);
if (err)
return err;
}
spin_lock(&file->f_lock);
file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
file->f_iocb_flags = iocb_flags(file);
spin_unlock(&file->f_lock);
return 0;
}
static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
bool allow_meta)
{
struct dentry *dentry = file_dentry(file);
struct path realpath;
int err;
real->flags = 0;
real->file = file->private_data;
if (allow_meta) {
ovl_path_real(dentry, &realpath);
} else {
/* lazy lookup and verify of lowerdata */
err = ovl_verify_lowerdata(dentry);
if (err)
return err;
ovl_path_realdata(dentry, &realpath);
}
if (!realpath.dentry)
return -EIO;
/* Has it been copied up since we'd opened it? */
if (unlikely(file_inode(real->file) != d_inode(realpath.dentry))) {
real->flags = FDPUT_FPUT;
real->file = ovl_open_realfile(file, &realpath);
return PTR_ERR_OR_ZERO(real->file);
}
/* Did the flags change since open? */
if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
return ovl_change_flags(real->file, file->f_flags);
return 0;
}
static int ovl_real_fdget(const struct file *file, struct fd *real)
{
if (d_is_dir(file_dentry(file))) {
real->flags = 0;
real->file = ovl_dir_real_file(file, false);
return PTR_ERR_OR_ZERO(real->file);
}
return ovl_real_fdget_meta(file, real, false);
}
static int ovl_open(struct inode *inode, struct file *file)
{
struct dentry *dentry = file_dentry(file);
struct file *realfile;
struct path realpath;
int err;
/* lazy lookup and verify lowerdata */
err = ovl_verify_lowerdata(dentry);
if (err)
return err;
err = ovl_maybe_copy_up(dentry, file->f_flags);
if (err)
return err;
/* No longer need these flags, so don't pass them on to underlying fs */
file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
ovl_path_realdata(dentry, &realpath);
if (!realpath.dentry)
return -EIO;
realfile = ovl_open_realfile(file, &realpath);
if (IS_ERR(realfile))
return PTR_ERR(realfile);
file->private_data = realfile;
return 0;
}
static int ovl_release(struct inode *inode, struct file *file)
{
fput(file->private_data);
return 0;
}
static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
{
struct inode *inode = file_inode(file);
struct fd real;
const struct cred *old_cred;
loff_t ret;
/*
* The two special cases below do not need to involve real fs,
* so we can optimizing concurrent callers.
*/
if (offset == 0) {
if (whence == SEEK_CUR)
return file->f_pos;
if (whence == SEEK_SET)
return vfs_setpos(file, 0, 0);
}
ret = ovl_real_fdget(file, &real);
if (ret)
return ret;
/*
* Overlay file f_pos is the master copy that is preserved
* through copy up and modified on read/write, but only real
* fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
* limitations that are more strict than ->s_maxbytes for specific
* files, so we use the real file to perform seeks.
*/
ovl_inode_lock(inode);
real.file->f_pos = file->f_pos;
old_cred = ovl_override_creds(inode->i_sb);
ret = vfs_llseek(real.file, offset, whence);
revert_creds(old_cred);
file->f_pos = real.file->f_pos;
ovl_inode_unlock(inode);
fdput(real);
return ret;
}
static void ovl_file_modified(struct file *file)
{
/* Update size/mtime */
ovl_copyattr(file_inode(file));
}
static void ovl_file_accessed(struct file *file)
{
struct inode *inode, *upperinode;
struct timespec64 ctime, uctime;
struct timespec64 mtime, umtime;
if (file->f_flags & O_NOATIME)
return;
inode = file_inode(file);
upperinode = ovl_inode_upper(inode);
if (!upperinode)
return;
ctime = inode_get_ctime(inode);
uctime = inode_get_ctime(upperinode);
mtime = inode_get_mtime(inode);
umtime = inode_get_mtime(upperinode);
if ((!timespec64_equal(&mtime, &umtime)) ||
!timespec64_equal(&ctime, &uctime)) {
inode_set_mtime_to_ts(inode, inode_get_mtime(upperinode));
inode_set_ctime_to_ts(inode, uctime);
}
touch_atime(&file->f_path);
}
static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct fd real;
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ovl_creds(file_inode(file)->i_sb),
.user_file = file,
.accessed = ovl_file_accessed,
};
if (!iov_iter_count(iter))
return 0;
ret = ovl_real_fdget(file, &real);
if (ret)
return ret;
ret = backing_file_read_iter(real.file, iter, iocb, iocb->ki_flags,
&ctx);
fdput(real);
return ret;
}
static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
struct fd real;
ssize_t ret;
int ifl = iocb->ki_flags;
struct backing_file_ctx ctx = {
.cred = ovl_creds(inode->i_sb),
.user_file = file,
.end_write = ovl_file_modified,
};
if (!iov_iter_count(iter))
return 0;
inode_lock(inode);
/* Update mode */
ovl_copyattr(inode);
ret = ovl_real_fdget(file, &real);
if (ret)
goto out_unlock;
if (!ovl_should_sync(OVL_FS(inode->i_sb)))
ifl &= ~(IOCB_DSYNC | IOCB_SYNC);
/*
* Overlayfs doesn't support deferred completions, don't copy
* this property in case it is set by the issuer.
*/
ifl &= ~IOCB_DIO_CALLER_COMP;
ret = backing_file_write_iter(real.file, iter, iocb, ifl, &ctx);
fdput(real);
out_unlock:
inode_unlock(inode);
return ret;
}
static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
struct fd real;
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ovl_creds(file_inode(in)->i_sb),
.user_file = in,
.accessed = ovl_file_accessed,
};
ret = ovl_real_fdget(in, &real);
if (ret)
return ret;
ret = backing_file_splice_read(real.file, ppos, pipe, len, flags, &ctx);
fdput(real);
return ret;
}
/*
* Calling iter_file_splice_write() directly from overlay's f_op may deadlock
* due to lock order inversion between pipe->mutex in iter_file_splice_write()
* and file_start_write(real.file) in ovl_write_iter().
*
* So do everything ovl_write_iter() does and call iter_file_splice_write() on
* the real file.
*/
static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
struct fd real;
struct inode *inode = file_inode(out);
ssize_t ret;
struct backing_file_ctx ctx = {
.cred = ovl_creds(inode->i_sb),
.user_file = out,
.end_write = ovl_file_modified,
};
inode_lock(inode);
/* Update mode */
ovl_copyattr(inode);
ret = ovl_real_fdget(out, &real);
if (ret)
goto out_unlock;
ret = backing_file_splice_write(pipe, real.file, ppos, len, flags, &ctx);
fdput(real);
out_unlock:
inode_unlock(inode);
return ret;
}
static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
struct fd real;
const struct cred *old_cred;
int ret;
ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
if (ret <= 0)
return ret;
ret = ovl_real_fdget_meta(file, &real, !datasync);
if (ret)
return ret;
/* Don't sync lower file for fear of receiving EROFS error */
if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fsync_range(real.file, start, end, datasync);
revert_creds(old_cred);
}
fdput(real);
return ret;
}
static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
{
struct file *realfile = file->private_data;
struct backing_file_ctx ctx = {
.cred = ovl_creds(file_inode(file)->i_sb),
.user_file = file,
.accessed = ovl_file_accessed,
};
return backing_file_mmap(realfile, vma, &ctx);
}
static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
struct inode *inode = file_inode(file);
struct fd real;
const struct cred *old_cred;
int ret;
inode_lock(inode);
/* Update mode */
ovl_copyattr(inode);
ret = file_remove_privs(file);
if (ret)
goto out_unlock;
ret = ovl_real_fdget(file, &real);
if (ret)
goto out_unlock;
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fallocate(real.file, mode, offset, len);
revert_creds(old_cred);
/* Update size */
ovl_file_modified(file);
fdput(real);
out_unlock:
inode_unlock(inode);
return ret;
}
static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
{
struct fd real;
const struct cred *old_cred;
int ret;
ret = ovl_real_fdget(file, &real);
if (ret)
return ret;
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = vfs_fadvise(real.file, offset, len, advice);
revert_creds(old_cred);
fdput(real);
return ret;
}
enum ovl_copyop {
OVL_COPY,
OVL_CLONE,
OVL_DEDUPE,
};
static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int flags, enum ovl_copyop op)
{
struct inode *inode_out = file_inode(file_out);
struct fd real_in, real_out;
const struct cred *old_cred;
loff_t ret;
inode_lock(inode_out);
if (op != OVL_DEDUPE) {
/* Update mode */
ovl_copyattr(inode_out);
ret = file_remove_privs(file_out);
if (ret)
goto out_unlock;
}
ret = ovl_real_fdget(file_out, &real_out);
if (ret)
goto out_unlock;
ret = ovl_real_fdget(file_in, &real_in);
if (ret) {
fdput(real_out);
goto out_unlock;
}
old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
switch (op) {
case OVL_COPY:
ret = vfs_copy_file_range(real_in.file, pos_in,
real_out.file, pos_out, len, flags);
break;
case OVL_CLONE:
ret = vfs_clone_file_range(real_in.file, pos_in,
real_out.file, pos_out, len, flags);
break;
case OVL_DEDUPE:
ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
real_out.file, pos_out, len,
flags);
break;
}
revert_creds(old_cred);
/* Update size */
ovl_file_modified(file_out);
fdput(real_in);
fdput(real_out);
out_unlock:
inode_unlock(inode_out);
return ret;
}
static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
size_t len, unsigned int flags)
{
return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
OVL_COPY);
}
static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int remap_flags)
{
enum ovl_copyop op;
if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
return -EINVAL;
if (remap_flags & REMAP_FILE_DEDUP)
op = OVL_DEDUPE;
else
op = OVL_CLONE;
/*
* Don't copy up because of a dedupe request, this wouldn't make sense
* most of the time (data would be duplicated instead of deduplicated).
*/
if (op == OVL_DEDUPE &&
(!ovl_inode_upper(file_inode(file_in)) ||
!ovl_inode_upper(file_inode(file_out))))
return -EPERM;
return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
remap_flags, op);
}
static int ovl_flush(struct file *file, fl_owner_t id)
{
struct fd real;
const struct cred *old_cred;
int err;
err = ovl_real_fdget(file, &real);
if (err)
return err;
if (real.file->f_op->flush) {
old_cred = ovl_override_creds(file_inode(file)->i_sb);
err = real.file->f_op->flush(real.file, id);
revert_creds(old_cred);
}
fdput(real);
return err;
}
const struct file_operations ovl_file_operations = {
.open = ovl_open,
.release = ovl_release,
.llseek = ovl_llseek,
.read_iter = ovl_read_iter,
.write_iter = ovl_write_iter,
.fsync = ovl_fsync,
.mmap = ovl_mmap,
.fallocate = ovl_fallocate,
.fadvise = ovl_fadvise,
.flush = ovl_flush,
.splice_read = ovl_splice_read,
.splice_write = ovl_splice_write,
.copy_file_range = ovl_copy_file_range,
.remap_file_range = ovl_remap_file_range,
};