[syzbot] [integrity?] [lsm?] possible deadlock in process_measurement (4)

[Shu Han]

> My apologies for the delay on this, I was traveling for a bit and
> missed this issue while away.
>
> Looking quickly at the report, I don't believe this is a false positive.

This is the mistake I made when I first watched the report.

It should be a deadlock.

> Looking at the IMA code, specifically the process_measurement()
> function which is called from the security_mmap_file() LSM hook, I'm
> not sure why there is the inode_lock() protected region.  Mimi?
> Roberto?  My best guess is that locking the inode may have been
> necessary before we moved the IMA inode state into the inode's LSM
> security blob, but I'm not certain.
>
> Mimi and Roberto, can we safely remove the inode locking in
> process_measurement()?

It would be better if IMA could avoid acqurie inode_lock().

If not, then we may need to consider solutions I mentioned in my
previous reply.