On 12.08.21 20:10, Linus Torvalds wrote:
On Thu, Aug 12, 2021 at 7:48 AM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:
Given that MAP_PRIVATE for shared libraries is our strategy for handling
writes to shared libraries perhaps we just need to use MAP_POPULATE or a
new related flag (perhaps MAP_PRIVATE_NOW)
No. That would be horrible for the usual bloated GUI libraries. It
might help some (dynamic page faults are not cheap either), but it
would hurt a lot.
Right, we most certainly don't want to waste system ram / swap space,
memory for page tables, and degrade performance just because some
corner-case nasty user space could harm itself.
This is definitely a "if you overwrite a system library while it's
being used, you get to keep both pieces" situation.
Right, play stupid games, win stupid prices. I agree that if there would
be an efficient way to detect+handle such overwrites gracefully, it
would be great to have the kernel support that. ETXTBUSY as implemented
with this series (but also before this series) is really only a
minimalistic approach to help detect some issues regarding the main
executable.
--
Thanks,
David / dhildenb
