Provide a type-safe interface for setting filesystem capabilities and a
generic implementation suitable for most filesystems.
Signed-off-by: Seth Forshee (DigitalOcean) <sforshee@xxxxxxxxxx>
---
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
