Re: [PATCH] coredump - as root not only if euid switched

[Andrew Morton <akpm@osdl.org>]

Peter Wächtler <pwaechtler@mac.com> wrote:
>
> While it's more secure to not dump core at all if the program has
>  switched euid, it's also very unpractical. Since only programs 
>  started from root, being setuid root or have CAP_SETUID it's far 
>  more practical to dump as root.root mode 600. This is the bahavior 
>  of Solaris.
> 
>  The current implementation does not ensure that an existing core
>  file is only readable as root, i.e. after dumping the ownership 
>  and mode is unchanged.
> 
>  Besides mm->dumpable to avoid recursive core dumps, on setuid files 
>  the dumpable flag still prevents a core dump while seteuid & co will
>  result in a core only readable as root.

It's a bit sad to add another function call level to sys_unlink() simply
because the core dumping code needs it.

Is it not possible to call sys_unlink() directly from there?  Something like

long kernel_unlink(const char *name)
{
	mm_segment_t old_fs = get_fs();
	long ret;

	set_fs(KERNEL_DS);
	ret = sys_unlink(name);
	set_fs(old_fs);
	return ret;
}