Re: [PATCH v8 07/10] x86, mpx: decode MPX instruction to get bound violation information

[Thomas Gleixner]

On Fri, 12 Sep 2014, H. Peter Anvin wrote:
> The correct limit is 15 bytes, not anything else, so this is a bug in
> the existing decoder.  A sequence of bytes longer than 15 bytes will

Fine. Lets fix it there.

> #UD, regardless of being "otherwise valid".

> Keep in mind the instruction may not be aligned, and you could fit an
> instruction plus a jump and still overrun a page in 15 bytes.

Fair enough. OTOH, I doubt that a text mapping will end exactly at
that jump after the MPX instruction.

So that's simple to fix.

Kill the hardcoded limit in lib/insn.c and let the callsites hand in a
lenght argument. So you can still use it for MPX and avoid 200 lines
of blindly copied and slightly different decoder code.

Thanks,

	tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/