| Message ID | 20210727104900.829215-2-brauner@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: support idmapped mounts | expand |
On Tue, Jul 27, 2021 at 12:48:40PM +0200, Christian Brauner wrote: > From: Christian Brauner <christian.brauner@ubuntu.com> > > Various filesystems rely on the lookup_one_len() helper to lookup a single path > component relative to a well-known starting point. Allow such filesystems to > support idmapped mounts by adding a version of this helper to take the idmap > into account when calling inode_permission(). This change is a required to let > btrfs (and other filesystems) support idmapped mounts. > > Cc: Christoph Hellwig <hch@infradead.org> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: Matthew Wilcox (Oracle) <willy@infradead.org> > Cc: linux-fsdevel@vger.kernel.org > Reviewed-by: Josef Bacik <josef@toxicpanda.com> > Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> > --- Christoph, Matthew are you ok with this now? Christian > /* v2 */ > - Al Viro <viro@zeniv.linux.org.uk>: > - Add a new lookup helper instead of changing the old ones. > > /* v3 */ > unchanged > > /* v4 */ > - Christoph Hellwig <hch@infradead.org>, > Matthew Wilcox (Oracle) <willy@infradead.org>: > - Simplify the name of lookup_mapped_one_len() to either lookup_one_mapped() > or lookup_one(). The *_len() prefix in all those helper apparently just > exists for historical reasons because we used to have lookup_dentry(), then > grew lookup_one(), and then grew lookup_one_len(). > --- > fs/namei.c | 43 +++++++++++++++++++++++++++++++++++++------ > include/linux/namei.h | 2 ++ > 2 files changed, 39 insertions(+), 6 deletions(-) > > diff --git a/fs/namei.c b/fs/namei.c > index bf6d8a738c59..902df46e7dd3 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -2575,8 +2575,9 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, > } > EXPORT_SYMBOL(vfs_path_lookup); > > -static int lookup_one_len_common(const char *name, struct dentry *base, > - int len, struct qstr *this) > +static int lookup_one_common(struct user_namespace *mnt_userns, > + const char *name, struct dentry *base, int len, > + struct qstr *this) > { > this->name = name; > this->len = len; > @@ -2604,7 +2605,7 @@ static int lookup_one_len_common(const char *name, struct dentry *base, > return err; > } > > - return inode_permission(&init_user_ns, base->d_inode, MAY_EXEC); > + return inode_permission(mnt_userns, base->d_inode, MAY_EXEC); > } > > /** > @@ -2628,7 +2629,7 @@ struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len > > WARN_ON_ONCE(!inode_is_locked(base->d_inode)); > > - err = lookup_one_len_common(name, base, len, &this); > + err = lookup_one_common(&init_user_ns, name, base, len, &this); > if (err) > return ERR_PTR(err); > > @@ -2655,7 +2656,7 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) > > WARN_ON_ONCE(!inode_is_locked(base->d_inode)); > > - err = lookup_one_len_common(name, base, len, &this); > + err = lookup_one_common(&init_user_ns, name, base, len, &this); > if (err) > return ERR_PTR(err); > > @@ -2664,6 +2665,36 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) > } > EXPORT_SYMBOL(lookup_one_len); > > +/** > + * lookup_one - filesystem helper to lookup single pathname component > + * @mnt_userns: user namespace of the mount the lookup is performed from > + * @name: pathname component to lookup > + * @base: base directory to lookup from > + * @len: maximum length @len should be interpreted to > + * > + * Note that this routine is purely a helper for filesystem usage and should > + * not be called by generic code. > + * > + * The caller must hold base->i_mutex. > + */ > +struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name, > + struct dentry *base, int len) > +{ > + struct dentry *dentry; > + struct qstr this; > + int err; > + > + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); > + > + err = lookup_one_common(mnt_userns, name, base, len, &this); > + if (err) > + return ERR_PTR(err); > + > + dentry = lookup_dcache(&this, base, 0); > + return dentry ? dentry : __lookup_slow(&this, base, 0); > +} > +EXPORT_SYMBOL(lookup_one); > + > /** > * lookup_one_len_unlocked - filesystem helper to lookup single pathname component > * @name: pathname component to lookup > @@ -2683,7 +2714,7 @@ struct dentry *lookup_one_len_unlocked(const char *name, > int err; > struct dentry *ret; > > - err = lookup_one_len_common(name, base, len, &this); > + err = lookup_one_common(&init_user_ns, name, base, len, &this); > if (err) > return ERR_PTR(err); > > diff --git a/include/linux/namei.h b/include/linux/namei.h > index be9a2b349ca7..df106b6d3cc5 100644 > --- a/include/linux/namei.h > +++ b/include/linux/namei.h > @@ -68,6 +68,8 @@ extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int); > extern struct dentry *lookup_one_len(const char *, struct dentry *, int); > extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int); > extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int); > +extern struct dentry *lookup_one(struct user_namespace *, const char *, > + struct dentry *, int); > > extern int follow_down_one(struct path *); > extern int follow_down(struct path *); > -- > 2.30.2 >
No need for the extern on the prototype, but otherwise looks good:
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/namei.c b/fs/namei.c index bf6d8a738c59..902df46e7dd3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2575,8 +2575,9 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, } EXPORT_SYMBOL(vfs_path_lookup); -static int lookup_one_len_common(const char *name, struct dentry *base, - int len, struct qstr *this) +static int lookup_one_common(struct user_namespace *mnt_userns, + const char *name, struct dentry *base, int len, + struct qstr *this) { this->name = name; this->len = len; @@ -2604,7 +2605,7 @@ static int lookup_one_len_common(const char *name, struct dentry *base, return err; } - return inode_permission(&init_user_ns, base->d_inode, MAY_EXEC); + return inode_permission(mnt_userns, base->d_inode, MAY_EXEC); } /** @@ -2628,7 +2629,7 @@ struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len WARN_ON_ONCE(!inode_is_locked(base->d_inode)); - err = lookup_one_len_common(name, base, len, &this); + err = lookup_one_common(&init_user_ns, name, base, len, &this); if (err) return ERR_PTR(err); @@ -2655,7 +2656,7 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) WARN_ON_ONCE(!inode_is_locked(base->d_inode)); - err = lookup_one_len_common(name, base, len, &this); + err = lookup_one_common(&init_user_ns, name, base, len, &this); if (err) return ERR_PTR(err); @@ -2664,6 +2665,36 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) } EXPORT_SYMBOL(lookup_one_len); +/** + * lookup_one - filesystem helper to lookup single pathname component + * @mnt_userns: user namespace of the mount the lookup is performed from + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * The caller must hold base->i_mutex. + */ +struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name, + struct dentry *base, int len) +{ + struct dentry *dentry; + struct qstr this; + int err; + + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); + + err = lookup_one_common(mnt_userns, name, base, len, &this); + if (err) + return ERR_PTR(err); + + dentry = lookup_dcache(&this, base, 0); + return dentry ? dentry : __lookup_slow(&this, base, 0); +} +EXPORT_SYMBOL(lookup_one); + /** * lookup_one_len_unlocked - filesystem helper to lookup single pathname component * @name: pathname component to lookup @@ -2683,7 +2714,7 @@ struct dentry *lookup_one_len_unlocked(const char *name, int err; struct dentry *ret; - err = lookup_one_len_common(name, base, len, &this); + err = lookup_one_common(&init_user_ns, name, base, len, &this); if (err) return ERR_PTR(err); diff --git a/include/linux/namei.h b/include/linux/namei.h index be9a2b349ca7..df106b6d3cc5 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -68,6 +68,8 @@ extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int); extern struct dentry *lookup_one_len(const char *, struct dentry *, int); extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int); extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int); +extern struct dentry *lookup_one(struct user_namespace *, const char *, + struct dentry *, int); extern int follow_down_one(struct path *); extern int follow_down(struct path *);