attr: handle idmapped mounts
When file attributes are changed most filesystems rely on the
setattr_prepare(), setattr_copy(), and notify_change() helpers for
initialization and permission checking. Let them handle idmapped mounts.
If the inode is accessed through an idmapped mount map it into the
mount's user namespace. Afterwards the checks are identical to
non-idmapped mounts. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.
Helpers that perform checks on the ia_uid and ia_gid fields in struct
iattr assume that ia_uid and ia_gid are intended values and have already
been mapped correctly at the userspace-kernelspace boundary as we
already do today. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index a83b3a8..27554f7 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -2610,7 +2610,7 @@ cifs_setattr_unix(struct dentry *direntry, struct iattr *attrs)
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_PERM)
attrs->ia_valid |= ATTR_FORCE;
- rc = setattr_prepare(direntry, attrs);
+ rc = setattr_prepare(&init_user_ns, direntry, attrs);
if (rc < 0)
goto out;
@@ -2715,7 +2715,7 @@ cifs_setattr_unix(struct dentry *direntry, struct iattr *attrs)
attrs->ia_size != i_size_read(inode))
truncate_setsize(inode, attrs->ia_size);
- setattr_copy(inode, attrs);
+ setattr_copy(&init_user_ns, inode, attrs);
mark_inode_dirty(inode);
/* force revalidate when any of these times are set since some
@@ -2757,7 +2757,7 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs)
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_PERM)
attrs->ia_valid |= ATTR_FORCE;
- rc = setattr_prepare(direntry, attrs);
+ rc = setattr_prepare(&init_user_ns, direntry, attrs);
if (rc < 0) {
free_xid(xid);
return rc;
@@ -2913,7 +2913,7 @@ cifs_setattr_nounix(struct dentry *direntry, struct iattr *attrs)
attrs->ia_size != i_size_read(inode))
truncate_setsize(inode, attrs->ia_size);
- setattr_copy(inode, attrs);
+ setattr_copy(&init_user_ns, inode, attrs);
mark_inode_dirty(inode);
cifs_setattr_exit:
