Miloslav Trmač writes:
On Tue, Jul 17, 2012 at 4:37 AM, Sam Varshavchik <mrsam@xxxxxxxxxxxxxxx> wrote:> Scott Schmit writes: >> And what's the pathname of a deleted file? > > My point exactly. There is none. Thanks, prelink! "Thanks, UNIX". What is the pathname of a file with several links?
Doesn't matter, either one of them is fine.
The pathnames just doesn't mean much in UNIX, and this case is _not_ particularly special.
Yes, let's get rid of filesystems, and store everything in a relational database. Isn't that something that a convicted monopolist tried to do, the other day?
> > Can you explain, then, the "correctly" approach by which an executable can > affirm whether another pid is either running the same executable, or the > post-prelinked version of the same executable. The executable _doesn't_ affirm that. This affirmation has zero security value due to ptrace(2) (or plain mmap(2) replacing the old executable with something different), and I can't see any non-security purpose of this check either.
Just because that you see zero value of this, and that you see no purpose from it, doesn't mean that there is none.
If you don't tell us what you are
_actually_ trying to do, instead of fixating on a sub-task that is
impossible or meaningless in UNIX, I'm afraid you'll stay
disappointed.
I already described what I'm doing, but I don't really feel like listening again to someone who firmly believes that they know what I'm doing better than me.
> P.P.S. And I'm still trying to process the concept of a symbolic link> pointing to a non-existent pathname; yet an open() on that somehow succeeds,> nevertheless. That's one a headscratcher, even though I'm told that's how > "UNIX" worked for decades. You always learn something new. Other traditional examples: /dev/std{in,out,err} (OK, these used to be devices rather than symlinks, but that's a trivial difference),
Really? An example of a "symbolic link pointing to a non-existent pathname"?
lrwxrwxrwx. 1 root root 15 Jul 17 18:02 /dev/stderr → /proc/self/fd/2
lrwxrwxrwx. 1 root root 15 Jul 17 18:02 /dev/stdin → /proc/self/fd/0
lrwxrwxrwx. 1 root root 15 Jul 17 18:02 /dev/stdout → /proc/self/fd/1
You mean to tell me that none of those symlinks exist? Could've fooled me:
[mrsam@eee900 /]$ ls -al /proc/self/fd/{0,1,2}
lrwx------. 1 mrsam mrsam 64 Jul 17 18:31 /proc/self/fd/0 → /dev/pts/1
lrwx------. 1 mrsam mrsam 64 Jul 17 18:31 /proc/self/fd/1 → /dev/pts/1
lrwx------. 1 mrsam mrsam 64 Jul 17 18:31 /proc/self/fd/2 → /dev/pts/1
But they do!
crw--w----. 1 mrsam tty 136, 1 Jul 17 18:31 /dev/pts/1
And that symlink exists as well! And I can even open it!
[mrsam@eee900 /]$ cat /dev/pts/1
Wow, what a novel concept.
So, can you try again, with an example of a symlink that points to a non-
existent pathname, yet one that can be open(), like /proc/self/exe →
"$filename (deleted)" can.
But, again, that's a sideshow and a distraction. That's not a problem, or an issue, of course. The problem is prelink invalidating the symlink, with the sorry excuses from the "duh… but you can still open it" crowd, who are incapable of understanding what the issue is.
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