Re: [PATCH 11/18] maccess: remove strncpy_from_unsafe

On Wed, 13 May 2020 16:59:40 -0700
Linus Torvalds [off-list ref] wrote:

On Wed, May 13, 2020 at 4:21 PM Masami Hiramatsu [off-list ref] wrote:

quoted

For trace_kprobe.c current order (kernel -> user fallback) is preferred
because it has another function dedicated for user memory.

Well, then it should just use the "strict" kernel-only one for the
non-user memory.

But yes, if there are legacy interfaces, then we might want to say
"these continue to work for the legacy case on platforms where we can
tell which kind of pointer it is from the bit pattern".

Yes, that was why I changed my mind and send reviewed-by last time.

https://lore.kernel.org/bpf/20200511142716.f1ff6fc55220012982c47fec@kernel.org/ (local)

But we should likely at least disallow it entirely on platforms where
we really can't - or pick one hardcoded choice. On sparc, you really
_have_ to specify one or the other.

OK. BTW, is there any way to detect the kernel/user space overlap on
memory layout statically? If there, I can do it. (I don't like
"if (CONFIG_X86)" thing....)
Or, maybe we need CONFIG_ARCH_OVERLAP_ADDRESS_SPACE?

Thank you,

-- 
Masami Hiramatsu [off-list ref]