On Fri, Jan 03, 2014 at 04:41:10PM +0100, Andreas Schwab wrote: > Heiko Carstens <heiko.carstens@xxxxxxxxxx> writes: > > > There is also other code that relies on this: e.g. copy_mount_options() my be > > called with KERNEL_DS. > > With KERNEL_DS you can *only* access kernel memory, which is unpagable. > If you want to access user memory, you _must_ use USER_DS. I didn't say anything else. copy_mount_options() will be called with KERNEL_DS from e.g. do_mount_root(). > > If DEBUG_PAGEALLOC is turned on, it would crash badly in kernel space > > if it crosses page boundaries and touches an invalid page, even though > > it should survive... > > Accessing an invalid page in kernel space is _always_ a bug. Even though the current futex check relies on working exception handling for this case. If the patch I posted gets merged as well, it really doesn't matter for me. Martin and I discussed this today and we will change the s390 code so that it will also survive very early USER_DS accesses (without valid current->mm) since we also discovered a couple of other oddities in our code. But theses changes would be too complex for -stable, imho. -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
