On Mon, 2022-11-21 at 18:55 -0500, Paul Moore wrote:

On Mon, Nov 21, 2022 at 3:54 PM Mimi Zohar [off-list ref] wrote:

quoted

On Mon, 2022-11-21 at 10:45 +0100, Roberto Sassu wrote:

quoted

quoted

As ocfs2 already defines initxattrs, that leaves only reiserfs missing
initxattrs().  A better, cleaner solution would be to define one.

If I understood why security_old_inode_init_security() is called
instead of security_inode_init_security(), the reason seems that the
filesystem code uses the length of the obtained xattr to make some
calculations (e.g. reserve space). The xattr is written at a later
time.

Since for reiserfs there is a plan to deprecate it, it probably
wouldn't be worth to support the creation of multiple xattrs. I would
define a callback to take the first xattr and make a copy, so that
calling security_inode_init_security() + reiserfs_initxattrs() is
equivalent to calling security_old_inode_init_security().

FWIW, reiserfs isn't going to be removed until 2025, I'm hopeful we
can remove the IMA/EVM special cases before then :)

Well, we are not that far...

quoted

quoted

But then, this is what anyway I was doing with the
security_initxattrs() callback, for all callers of security_old_inode_i
nit_security().

Also, security_old_inode_init_security() is exported to kernel modules.
Maybe, it is used somewhere. So, unless we plan to remove it
completely, it should be probably be fixed to avoid multiple LSMs
successfully setting an xattr, and losing the memory of all except the
last (which this patch fixes by calling security_inode_init_security()).

I would much rather remove security_old_inode_init_security() then
worry about what out-of-tree modules might be using it.  Hopefully we
can resolve the ocfs2 usage and get ocfs2 exclusively on the new hook
without too much trouble, which means all we have left is reiserfs ...
how difficult would you expect the conversion to be for reiserfs?

Ok for removing security_old_inode_init_security().

For reiserfs, I guess maintaining the current behavior of setting only
one xattr should be easy. For multiple xattrs, I need to understand
exactly how many blocks need to be reserved.

quoted

quoted

If there is still the preference, I will implement the reiserfs
callback and make a fix for security_old_inode_init_security().

There's no sense in doing both, as the purpose of defining a reiserfs
initxattrs function was to clean up this code making it more readable.

The fix for security_old_inode_init_security(), stopping at the first
LSM returning zero, was to avoid the memory leak. Will not be needed if
the function is removed.

Roberto