Re: remove set_fs calls from the exec and coredump code v2

Christoph Hellwig [off-list ref] writes:

On Fri, Apr 17, 2020 at 05:41:52PM -0500, Eric W. Biederman wrote:

quoted

quoted

this series gets rid of playing with the address limit in the exec and
coredump code.  Most of this was fairly trivial, the biggest changes are
those to the spufs coredump code.

Changes since v1:
 - properly spell NUL
 - properly handle the compat siginfo case in ELF coredumps

Quick question is exec from a kernel thread within the scope of what you
are looking at?

There is a set_fs(USER_DS) in flush_old_exec whose sole purpose appears
to be to allow exec from kernel threads.  Where the kernel threads
run with set_fs(KERNEL_DS) until they call exec.

This series doesn't really look at that area.  But I don't think exec
from a kernel thread makes any sense, and cleaning up how to set the
initial USER_DS vs KERNEL_DS state is something I'll eventually get to,
it seems like a major mess at the moment.

Fair enough.  I just wanted to make certain that it is on people's radar
that when the kernel exec's init the arguments are read from kernel
memory and the set_fs(USER_DS) in flush_old_exec() that makes that not
work later.

It is subtle and easy to miss.  So I figured I would mention it since
I have been staring at the exec code a lot lately.

Eric