Provide a type-safe interface for setting filesystem capabilities and a generic implementation suitable for most filesystems.
Signed-off-by: Seth Forshee (DigitalOcean) <[email protected]> --- fs/xattr.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 2 ++ 2 files changed, 89 insertions(+) diff --git a/fs/xattr.c b/fs/xattr.c index 3abaf9bef0a5..03cc824e4f87 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -247,6 +247,93 @@ int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, } EXPORT_SYMBOL(vfs_get_fscaps); +static int generic_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + const struct vfs_caps *caps, int flags) +{ + struct inode *inode = d_inode(dentry); + struct vfs_ns_cap_data nscaps; + int size; + + size = vfs_caps_to_xattr(idmap, i_user_ns(inode), caps, + &nscaps, sizeof(nscaps)); + if (size < 0) + return size; + + return __vfs_setxattr_noperm(idmap, dentry, XATTR_NAME_CAPS, + &nscaps, size, flags); +} + +/** + * vfs_set_fscaps - set filesystem capabilities + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry on which to set filesystem capabilities + * @caps: the filesystem capabilities to be written + * @flags: setxattr flags to use when writing the capabilities xattr + * + * This function writes the supplied filesystem capabilities to the dentry. + * + * Return: 0 on success, a negative errno on error. + */ +int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + const struct vfs_caps *caps, int flags) +{ + struct inode *inode = d_inode(dentry); + struct inode *delegated_inode = NULL; + struct vfs_ns_cap_data nscaps; + int size, error; + + /* + * Unfortunately EVM wants to have the raw xattr value to compare to + * the on-disk version, so we need to pass the raw xattr to the + * security hooks. But we also want to do security checks before + * breaking leases, so that means a conversion to the raw xattr here + * which will usually be reduntant with the conversion we do for + * writing the xattr to disk. + */ + size = vfs_caps_to_xattr(idmap, i_user_ns(inode), caps, &nscaps, + sizeof(nscaps)); + if (size < 0) + return size; + +retry_deleg: + inode_lock(inode); + + error = xattr_permission(idmap, inode, XATTR_NAME_CAPS, MAY_WRITE); + if (error) + goto out_inode_unlock; + error = security_inode_setxattr(idmap, dentry, XATTR_NAME_CAPS, &nscaps, + size, flags); + if (error) + goto out_inode_unlock; + + error = try_break_deleg(inode, &delegated_inode); + if (error) + goto out_inode_unlock; + + if (inode->i_opflags & IOP_XATTR) { + if (inode->i_op->set_fscaps) + error = inode->i_op->set_fscaps(idmap, dentry, caps, flags); + else + error = generic_set_fscaps(idmap, dentry, caps, flags); + } else if (unlikely(is_bad_inode(inode))) { + error = -EIO; + } else { + error = -EOPNOTSUPP; + } + +out_inode_unlock: + inode_unlock(inode); + + if (delegated_inode) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } + + return error; +} +EXPORT_SYMBOL(vfs_set_fscaps); + int __vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, struct inode *inode, const char *name, const void *value, diff --git a/include/linux/fs.h b/include/linux/fs.h index e25b39e4017a..80992e210b83 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2059,6 +2059,8 @@ extern int __vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, struct vfs_caps *caps); extern int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, struct vfs_caps *caps); +extern int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, + const struct vfs_caps *caps, int flags); enum freeze_holder { FREEZE_HOLDER_KERNEL = (1U << 0), -- 2.43.0
