On Mon, Apr 29, 2024 at 4:26 PM Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote:
>
> Combine inode creation with opening a file.
>
> There are six separate objects that are being set up: the backing inode,
> dentry and file, and the overlay inode, dentry and file. Cleanup in case
> of an error is a bit of a challenge and is difficult to test, so careful
> review is needed.
>
> All tmpfile testcases except generic/509 now run/pass, and no regressions
> are observed with full xfstests.
>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
I have nothing queued in the overlayfs tree for 6.10 and no plans
of driving any ovl work for 6.10, so feel free to use the overlayfs-next
branch to queue this patch.
Thanks,
Amir.
> ---
> v2:
> - don't pass real_idmap to backing_tmpfile_open()
> - move ovl_dir_modified() from ovl_instantiate() to callers
> - use ovl_instantiate() for tmpfile
> - call d_mark_tmpfile() before d_instantiate() in ovl_instantiate();
> no longer need to mess with nlink
> - extract helper ovl_setup_cred_for_create() from ovl_create_or_link()
> - don't apply umask to mode, VFS will do that when creating the tmpfile
> - add comment above file->private_data cleanup
>
> ---
> fs/backing-file.c | 23 ++++++
> fs/internal.h | 3 +
> fs/namei.c | 6 +-
> fs/overlayfs/dir.c | 145 ++++++++++++++++++++++++++++++-----
> fs/overlayfs/file.c | 3 -
> fs/overlayfs/overlayfs.h | 3 +
> include/linux/backing-file.h | 3 +
> 7 files changed, 161 insertions(+), 25 deletions(-)
>
> diff --git a/fs/backing-file.c b/fs/backing-file.c
> index 740185198db3..afb557446c27 100644
> --- a/fs/backing-file.c
> +++ b/fs/backing-file.c
> @@ -52,6 +52,29 @@ struct file *backing_file_open(const struct path *user_path, int flags,
> }
> EXPORT_SYMBOL_GPL(backing_file_open);
>
> +struct file *backing_tmpfile_open(const struct path *user_path, int flags,
> + const struct path *real_parentpath,
> + umode_t mode, const struct cred *cred)
> +{
> + struct mnt_idmap *real_idmap = mnt_idmap(real_parentpath->mnt);
> + struct file *f;
> + int error;
> +
> + f = alloc_empty_backing_file(flags, cred);
> + if (IS_ERR(f))
> + return f;
> +
> + path_get(user_path);
> + *backing_file_user_path(f) = *user_path;
> + error = vfs_tmpfile(real_idmap, real_parentpath, f, mode);
> + if (error) {
> + fput(f);
> + f = ERR_PTR(error);
> + }
> + return f;
> +}
> +EXPORT_SYMBOL(backing_tmpfile_open);
> +
> struct backing_aio {
> struct kiocb iocb;
> refcount_t ref;
> diff --git a/fs/internal.h b/fs/internal.h
> index 7ca738904e34..ab2225136f60 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -62,6 +62,9 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode);
> int do_symlinkat(struct filename *from, int newdfd, struct filename *to);
> int do_linkat(int olddfd, struct filename *old, int newdfd,
> struct filename *new, int flags);
> +int vfs_tmpfile(struct mnt_idmap *idmap,
> + const struct path *parentpath,
> + struct file *file, umode_t mode);
>
> /*
> * namespace.c
> diff --git a/fs/namei.c b/fs/namei.c
> index c5b2a25be7d0..13e50b0a49d2 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3668,9 +3668,9 @@ static int do_open(struct nameidata *nd,
> * On non-idmapped mounts or if permission checking is to be performed on the
> * raw inode simply pass @nop_mnt_idmap.
> */
> -static int vfs_tmpfile(struct mnt_idmap *idmap,
> - const struct path *parentpath,
> - struct file *file, umode_t mode)
> +int vfs_tmpfile(struct mnt_idmap *idmap,
> + const struct path *parentpath,
> + struct file *file, umode_t mode)
> {
> struct dentry *child;
> struct inode *dir = d_inode(parentpath->dentry);
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index 0f8b4a719237..cac21ef546fe 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -14,6 +14,7 @@
> #include <linux/posix_acl_xattr.h>
> #include <linux/atomic.h>
> #include <linux/ratelimit.h>
> +#include <linux/backing-file.h>
> #include "overlayfs.h"
>
> static unsigned short ovl_redirect_max = 256;
> @@ -260,14 +261,13 @@ static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
> * may not use to instantiate the new dentry.
> */
> static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
> - struct dentry *newdentry, bool hardlink)
> + struct dentry *newdentry, bool hardlink, struct file *tmpfile)
> {
> struct ovl_inode_params oip = {
> .upperdentry = newdentry,
> .newinode = inode,
> };
>
> - ovl_dir_modified(dentry->d_parent, false);
> ovl_dentry_set_upper_alias(dentry);
> ovl_dentry_init_reval(dentry, newdentry, NULL);
>
> @@ -295,6 +295,9 @@ static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
> inc_nlink(inode);
> }
>
> + if (tmpfile)
> + d_mark_tmpfile(tmpfile, inode);
> +
> d_instantiate(dentry, inode);
> if (inode != oip.newinode) {
> pr_warn_ratelimited("newly created inode found in cache (%pd2)\n",
> @@ -345,7 +348,8 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
> ovl_set_opaque(dentry, newdentry);
> }
>
> - err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);
> + ovl_dir_modified(dentry->d_parent, false);
> + err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink, NULL);
> if (err)
> goto out_cleanup;
> out_unlock:
> @@ -529,7 +533,8 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
> if (err)
> goto out_cleanup;
> }
> - err = ovl_instantiate(dentry, inode, newdentry, hardlink);
> + ovl_dir_modified(dentry->d_parent, false);
> + err = ovl_instantiate(dentry, inode, newdentry, hardlink, NULL);
> if (err) {
> ovl_cleanup(ofs, udir, newdentry);
> dput(newdentry);
> @@ -551,12 +556,35 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
> goto out_dput;
> }
>
> +static int ovl_setup_cred_for_create(struct dentry *dentry, struct inode *inode,
> + umode_t mode, const struct cred *old_cred)
> +{
> + int err;
> + struct cred *override_cred;
> +
> + override_cred = prepare_creds();
> + if (!override_cred)
> + return -ENOMEM;
> +
> + override_cred->fsuid = inode->i_uid;
> + override_cred->fsgid = inode->i_gid;
> + err = security_dentry_create_files_as(dentry, mode, &dentry->d_name,
> + old_cred, override_cred);
> + if (err) {
> + put_cred(override_cred);
> + return err;
> + }
> + put_cred(override_creds(override_cred));
> + put_cred(override_cred);
> +
> + return 0;
> +}
> +
> static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
> struct ovl_cattr *attr, bool origin)
> {
> int err;
> const struct cred *old_cred;
> - struct cred *override_cred;
> struct dentry *parent = dentry->d_parent;
>
> old_cred = ovl_override_creds(dentry->d_sb);
> @@ -572,10 +600,6 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
> }
>
> if (!attr->hardlink) {
> - err = -ENOMEM;
> - override_cred = prepare_creds();
> - if (!override_cred)
> - goto out_revert_creds;
> /*
> * In the creation cases(create, mkdir, mknod, symlink),
> * ovl should transfer current's fs{u,g}id to underlying
> @@ -589,17 +613,9 @@ static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
> * create a new inode, so just use the ovl mounter's
> * fs{u,g}id.
> */
> - override_cred->fsuid = inode->i_uid;
> - override_cred->fsgid = inode->i_gid;
> - err = security_dentry_create_files_as(dentry,
> - attr->mode, &dentry->d_name, old_cred,
> - override_cred);
> - if (err) {
> - put_cred(override_cred);
> + err = ovl_setup_cred_for_create(dentry, inode, attr->mode, old_cred);
> + if (err)
> goto out_revert_creds;
> - }
> - put_cred(override_creds(override_cred));
> - put_cred(override_cred);
> }
>
> if (!ovl_dentry_is_whiteout(dentry))
> @@ -1290,6 +1306,96 @@ static int ovl_rename(struct mnt_idmap *idmap, struct inode *olddir,
> return err;
> }
>
> +static int ovl_create_tmpfile(struct file *file, struct dentry *dentry,
> + struct inode *inode, umode_t mode)
> +{
> + const struct cred *old_cred;
> + struct path realparentpath;
> + struct file *realfile;
> + struct dentry *newdentry;
> + /* It's okay to set O_NOATIME, since the owner will be current fsuid */
> + int flags = file->f_flags | OVL_OPEN_FLAGS;
> + int err;
> +
> + err = ovl_copy_up(dentry->d_parent);
> + if (err)
> + return err;
> +
> + old_cred = ovl_override_creds(dentry->d_sb);
> + err = ovl_setup_cred_for_create(dentry, inode, mode, old_cred);
> + if (err)
> + goto out_revert_creds;
> +
> + ovl_path_upper(dentry->d_parent, &realparentpath);
> + realfile = backing_tmpfile_open(&file->f_path, flags, &realparentpath,
> + mode, current_cred());
> + err = PTR_ERR(realfile);
> + if (IS_ERR(realfile))
> + goto out_revert_creds;
> +
> + /* ovl_instantiate() consumes the newdentry reference on success */
> + newdentry = dget(realfile->f_path.dentry);
> + err = ovl_instantiate(dentry, inode, newdentry, false, file);
> + if (!err) {
> + file->private_data = realfile;
> + } else {
> + dput(newdentry);
> + fput(realfile);
> + }
> +out_revert_creds:
> + revert_creds(old_cred);
> + return err;
> +}
> +
> +static int ovl_dummy_open(struct inode *inode, struct file *file)
> +{
> + return 0;
> +}
> +
> +static int ovl_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
> + struct file *file, umode_t mode)
> +{
> + int err;
> + struct dentry *dentry = file->f_path.dentry;
> + struct inode *inode;
> +
> + err = ovl_want_write(dentry);
> + if (err)
> + return err;
> +
> + err = -ENOMEM;
> + inode = ovl_new_inode(dentry->d_sb, mode, 0);
> + if (!inode)
> + goto drop_write;
> +
> + inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
> + err = ovl_create_tmpfile(file, dentry, inode, inode->i_mode);
> + if (err)
> + goto put_inode;
> +
> + /*
> + * Check if the preallocated inode was actually used. Having something
> + * else assigned to the dentry shouldn't happen as that would indicate
> + * that the backing tmpfile "leaked" out of overlayfs.
> + */
> + err = -EIO;
> + if (WARN_ON(inode != d_inode(dentry)))
> + goto put_realfile;
> +
> + /* inode reference was transferred to dentry */
> + inode = NULL;
> + err = finish_open(file, dentry, ovl_dummy_open);
> +put_realfile:
> + /* Without FMODE_OPENED ->release() won't be called on @file */
> + if (!(file->f_mode & FMODE_OPENED))
> + fput(file->private_data);
> +put_inode:
> + iput(inode);
> +drop_write:
> + ovl_drop_write(dentry);
> + return err;
> +}
> +
> const struct inode_operations ovl_dir_inode_operations = {
> .lookup = ovl_lookup,
> .mkdir = ovl_mkdir,
> @@ -1310,4 +1416,5 @@ const struct inode_operations ovl_dir_inode_operations = {
> .update_time = ovl_update_time,
> .fileattr_get = ovl_fileattr_get,
> .fileattr_set = ovl_fileattr_set,
> + .tmpfile = ovl_tmpfile,
> };
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 05536964d37f..1a411cae57ed 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -24,9 +24,6 @@ static char ovl_whatisit(struct inode *inode, struct inode *realinode)
> 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)
> {
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index ee949f3e7c77..0bfe35da4b7b 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -175,6 +175,9 @@ static inline int ovl_metadata_digest_size(const struct ovl_metacopy *metacopy)
> return (int)metacopy->len - OVL_METACOPY_MIN_SIZE;
> }
>
> +/* No atime modification on underlying */
> +#define OVL_OPEN_FLAGS (O_NOATIME)
> +
> extern const char *const ovl_xattr_table[][2];
> static inline const char *ovl_xattr(struct ovl_fs *ofs, enum ovl_xattr ox)
> {
> diff --git a/include/linux/backing-file.h b/include/linux/backing-file.h
> index 3f1fe1774f1b..4b61b0e57720 100644
> --- a/include/linux/backing-file.h
> +++ b/include/linux/backing-file.h
> @@ -22,6 +22,9 @@ struct backing_file_ctx {
> struct file *backing_file_open(const struct path *user_path, int flags,
> const struct path *real_path,
> const struct cred *cred);
> +struct file *backing_tmpfile_open(const struct path *user_path, int flags,
> + const struct path *real_parentpath,
> + umode_t mode, const struct cred *cred);
> ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
> struct kiocb *iocb, int flags,
> struct backing_file_ctx *ctx);
> --
> 2.44.0
>
