Re: [PATCH net-next] modules: allow modprobe load regular elf binaries

[Linus Torvalds]

On Fri, Mar 9, 2018 at 10:48 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>> On Mar 9, 2018, at 10:17 AM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>>
>> Hmm. I wish we had an "execute blob" model, but we really don't, and
>> it would be hard/impossible to do without pinning the pages in memory.
>>
>
> Why so hard?  We can already execute a struct file for execveat, and Alexei already has this working for umh.
> Surely we can make an immutable (as in even root canât write it) kernel-internal tmpfs file, execveat it, then unlink it.

And what do you think that does? It pins the memory for the whole
time. As a *copy* of the original file.

Anyway, see my other suggestion that makes this all irrelevant. Just
wait synchronously (until the exit), and just use deny_write_access().

The "synchronous wait" means that you don't have the semantic change
(and really., it's *required* anyway for the whole mutual exclusion
against another thread racing to load the same module), and the
deny_write_access() means that we don't neeed to make another copy.

                Linus