Re: [PATCH 1/3] ima: Remove inode lock

[Roberto Sassu <roberto.sassu@huaweicloud.com>]

On Wed, 2024-10-09 at 23:59 +0800, Shu Han wrote:
> > Finally, expand the critical region in process_measurement()
> > guarded by
> > iint->mutex up to where the inode was locked, use only one iint
> > lock in
> > __ima_inode_hash(), since the mutex is now in the inode security
> > blob, and
> > replace the inode_lock()/inode_unlock() calls in
> > ima_check_last_writer().
> 
> I am not familiar with this, so the following statement may be
> inaccurate:
> 
> I suspect that modifying the `i_flags` field through
> `inode->i_flags |= S_IMA;` in `ima_inode_get` may cause a
> race, as this patch removes the write lock for inodes in
> process_measurement().
> 
> For example, swapon() adds the S_SWAPFILE tag under inode write
> lock's
> protection.
> 
> Perhaps this initialization tag(`S_IMA`) can also be moved into
> inode's
> security blob.

It would not even be necessary, since after making IMA as a regular LSM
the S_IMA check can be replaced by testing whether or not the pointer
of inode integrity metadata in the security blob is NULL.

Will remove S_IMA.

Thanks

Roberto