Re: [PATCH v3 1/4] kexec: simplify compat_sys_kexec_load

From: Christoph Hellwig
Date: Tue May 18 2021 - 02:41:52 EST

On Mon, May 17, 2021 at 10:57:24PM -0500, Eric W. Biederman wrote:
> We open ourselves up to bugs whenever we lie to the type system.
> Skimming through the code it looks like it should be possible
> to not need the in_compat_syscall and the casts to the wrong
> type by changing the order of the code a little bit.

What kind of bug do you expect? We must only copy from user addresses
once anyway. I've never seen bugs due the use of in_compat_syscall,
but plenty due to cruft code trying to avoid it.