Re: [PATCH] vsprintf: drop comment claiming %n is ignored

[George Spelvin]

> Why would you want to artificially make the function diverge
> from the spec?

Because %n make it easy to convert a not-uncommon format string bug into
a code injection.  Thus, poses a significant security vulnerability.

Since it's an obscure and  rarely-used feature, it is straightforward
to eliminate all users in the Linux kernel, making removing it possible.

I agree that if it were harmless, it would be useful to leave it
implemented just for simplicity (it's a trivial amount of code), but
it's not harmless.

> People shouldn't be caught by surprises if at all
> possible, and one can certainly not expect people to go look at
> the comment before the function implementation to find out
> what basic (standard) features _do not_ work (one can expect
> so when trying to find out about _extensions_).

This is why people propose implementing it as a kernel warning.

Strongly support this change.
--
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/