Messages in this thread | | | Date | Sun, 3 Jul 2011 22:10:31 +0100 | From | Alan Cox <> | Subject | Re: [PATCH v2] kernel: escape non-ASCII and control characters in printk() |
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> That said, if we really want to do this, I think doing it with %s > filtering is the only way, and it would make the default case where > people really don't think about possible user-supplied strings be > safe. > > So saying "%s is for pure 7-bit ASCII with no control codes" is > annoying, but would really fix it.
It's fairly easy for the console in question to provide a filter but 7bit ascii wouldn't be a bad default for a printing console, definitely a wrong default for the log file though.
> That said, I think it should be unconditional. None of this "safe vs > unsafe" flags, and none of this "printk format strings are different > from other vsprintf format strings". If special characters are a > potential security problem for printk(), then they are a potential > security problem for other things (eg /proc filenames or content etc).
In which case we can't do it because we need \n in proc content so that's a complete and utter non starter. In addition we have things with filenames in it and filenames are unicode so we'd break apps that look filenames up via /proc for things like monitoring.
It depends how much you care as well - any idiot can figure out how to simply use spaces and/or tabs to build multiple lines of fake looking output like say a spoofed Oops.
As Lars can no doubt remind people spoofing oopses can be fun ;)
Alan
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