Re: [patch -next] ath5k: snprintf() returns largish values

[Linus Torvalds]

On Fri, Jul 23, 2010 at 10:48 AM, Joe Perches <joe@xxxxxxxxxxx> wrote:
>
> There are also many repeated uses of snprintf in kernel sources
> that could similarly be a problem.
>
>        bar += snprintf(foo + bar, ...)
>        bar += snprintf(foo + bar, ...)
> or
>        foo += snprintf(foo, ...)
>        foo += snprintf(foo, ...)

As long as the number of bytes is updated correctly, this won't be a
security problem, although it can cause a (single) warning. The kernel
vsnprintf does

        if (WARN_ON_ONCE((int) size < 0))
                return 0;

so if somebody overflows a buffer with multiple snprintf calls, it
will all be ok as long as the buffer size thing is updated the natural
way (possibly using pointer arithmetic, eg "end - bar").

                Linus
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