Commit c2fd68b6 authored by Christian Brauner's avatar Christian Brauner Committed by David Sterba
Browse files

namei: add mapping aware lookup helper 



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: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent e7849e33

fs/namei.c

+37 −6
Original line number Diff line number Diff line
@@ -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);

include/linux/namei.h

+1 −0
Original line number Diff line number Diff line
@@ -68,6 +68,7 @@ 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);

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 *);