Re: [RESEND][PATCH] ima: Set and clear FMODE_CAN_READ in ima_calc_file_hash()

[Mimi Zohar]

On Tue, 2020-11-17 at 15:36 -0800, Linus Torvalds wrote:
> Another alternative is to change the policy and say "any write-only
> open gets turned into a read-write open".
> 
> But it needs to be done at *OPEN* time, not randomly afterwards by
> just lying to the 'struct file'.

The ima_file_check hook is at open, but it is immediately after
vfs_open().   Only after the file is opened can we determine if the
file is in policy.  If the file was originally opened without read
permission, a new file instance (dentry_open) with read permission is
opened.  Would limiting opening a new file instance with read
permission to just the ima_file_check hook be acceptable?

thanks,

Mimi