Messages in this thread | | | From | Andy Shevchenko <> | Date | Tue, 19 Feb 2019 13:06:17 +0200 | Subject | Re: [PATCH v6 9/9] vsprintf: Avoid confusion between invalid address and value |
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On Tue, Feb 19, 2019 at 5:07 AM Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote:
> Suppose, in my driver I want to sprintf() IPv4 address. The longest > possible address is 3 * 4 (%d%d%d) + 3 bytes (dots) + terminating NULL. > E.g. 111.111.111.111 > > So I can allocate a 16-bytes buffer (stack or slab) and accidentally > do an %piS sprintf() on a corrupted in_addr struct: > > char buf[16]; > sprintf(buf, "%piS", in_addr); > > forcing sprintf() to write "(invalid address)" to a 16-bytes buffer, > but the thing is - strlen("(invalid address)") > 16.
It would print as many characters as buffer allows. In your case above the use of sprintf() is a bit fragile.
But yes, the error messages should not be longer than 8 / 16 bytes depending on 32- or 64-bit build we have.
-- With Best Regards, Andy Shevchenko
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