On Mon, May 04 2015, Alexey Dobriyan <adobri...@gmail.com> wrote: >> There are lots of callers of memparse(), and I don't think any of them >> are prepared to handle *endp ending up pointing before the passed-in >> string (-EINVAL == -22, -ERANGE == -34). I can easily see how that could >> lead to an infinite loop, maybe worse. > > Yeah, possible bug could become worse, I'll add error checking, > but, seriously, you're defending this :^) > > case Opt_nr_inodes: > ===> /* memparse() will accept a K/M/G without a digit */ > ===> if (!isdigit(*args[0].from)) > ===> goto bad_val; > pconfig->nr_inodes = memparse(args[0].from, &rest); > break; >
No, I'm not defending memparse(), simple_strto* or any of their callers. I'm just trying to say that you can't change the semantics of memparse() without considering all its callers. I don't think there's any way to "add error checking" and preserve the exact memparse() semantic - in other words, I don't think simple_strto* can actually be implemented in terms of parse_integer. But that's not a bad thing - we want to get rid of those. > memparse() is misdesigned in the same sense strtoul() is misdesigned. > Every "memparse(s, NULL)" user is a bug for example. Yes, memparse is misdesigned, since it doesn't have a way to indicate error. That leads me to: There's no point in adding error checking to the integer parsing part without also checking the left shifts for overflow. I think the right approach is to rename memparse to legacy_memparse and introduce a memparse with semantics that allow error checking. One could start by introducing that under the name sane_memparse. But there are probably lots of simple_strto*() uses that are easier to eliminate. Rasmus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
