On Mon, Sep 2, 2024, at 07:06, Aleksa Sarai wrote:

While we do currently return -EFAULT in this case, it seems prudent to
follow the behaviour of other syscalls like clone3. It seems quite
unlikely that anyone depends on this error code being EFAULT, but we can
always revert this if it turns out to be an issue.

Right, it's probably a good idea to have a limit there rather than
having a busy loop with a user-provided length when the only bound is
the available virtual memory.

 	if (unlikely(usize < OPEN_HOW_SIZE_VER0))
 		return -EINVAL;
+	if (unlikely(usize > PAGE_SIZE))
+		return -E2BIG;

Is PAGE_SIZE significant here? If there is a need to enforce a limit,
I would expect this to be the same regardless of kernel configuration,
since the structure layout is also independent of the configuration.

Where is the current -EFAULT for users passing more than a page?
I only see it for reads beyond the VMA, but not e.g. when checking
terabytes of zero pages from an anonymous mapping.

    Arnd