Re: [Linux-ima-user] [PATCH] evm: add exceptions for inodes without getxattr() support.

[Mikhail K. <vie...@vi...>]

I found this kernel upstream patch:
https://github.com/torvalds/linux/commit/6c6ef9f26e598fb977f60935e109cd5b266c941a
From this patch description:
...
Filesystems that do not support xattrs on some inodes should clear the
IOP_XATTR i_opflags flag in those inodes.  (Right now, some filesystems
have checks to disable xattrs on some inodes in the ->list, ->get, and
->set xattr handler operations instead.)  The IOP_XATTR flag is
automatically cleared in inodes of filesystems that don't have xattr
support.
...


I was digging a little bit more in getxattr() in my kernel v4.7 (that
don't have IOP_XATTR related patches), and looks like this is true.
xattr_resolve_name() could not find ->get handler operation for inode
and return EOPNOTSUPP error.

We have inode->i_op->getxattr test that return true (since FS have
xattrs support), but as soon as inode->i_op->getxattr() called,
generic_getxattr() will be called (for ext4), that will call
xattr_resolve_name(), xattr_resolve_name() don't find ->get handler
operation and return EOPNOTSUPP error.

From one side we have FS will xattrs support, from another side,
we could have inode without ->list, ->get, and ->set xattr handler
operations, that probably should mean "xattrs is disabled for
this inode".


-- 
Best regards,
Mikhail Kurinnoi