Re: FTS not ready for a remount during traversal

[Jim Meyering]

Kamil Dudka wrote:
...
>> > Any idea how to solve the problem? Thanks in advance!
>>
>> I don't see how we can justify any such change.
>> Being able to detect whether the traversal returns to a previously
>> visited directory is required for security and reliability.  Weakening
>> that device/inode equality check by removing the device comparison part
>> would leave every fts-using tool open to a particularly subtle -- but
>> nonetheless serious -- type of attack.
>
> That's exactly why I've written another patch. The patch proposed by me does
> not bypass the ino/dev check on the return. It only updates the stat data
> right after opening a directory.

Oh!  I didn't look carefully enough at that one.
Have you measured the performance penalty it incurs?
I hope it is possible to do the same thing, but with less of a penalty.

I'm afraid we'll have to do something like that one way or
another.  At best, the impact will be so small that we won't
even have to provide a new "flag" to enable it.