RE: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'

Justin He
2021-06-15T07:06:37Z

Hi Rasmus

> -----Original Message-----
> From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Sent: Saturday, June 12, 2021 5:40 AM
> To: Justin He <Justin.He@arm.com>; Petr Mladek <pmladek@suse.com>; Steven
> Rostedt <rostedt@goodmis.org>; Sergey Senozhatsky
> <senozhatsky@chromium.org>; Andy Shevchenko
> <andriy.shevchenko@linux.intel.com>; Jonathan Corbet <corbet@lwn.net>;
> Alexander Viro <viro@zeniv.linux.org.uk>; Linus Torvalds <torvalds@linux-
> foundation.org>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>; Eric Biggers
> <ebiggers@google.com>; Ahmed S. Darwish <a.darwish@linutronix.de>; linux-
> doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
> fsdevel@vger.kernel.org
> Subject: Re: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'
>
> On 11/06/2021 17.59, Jia He wrote:
> > After the behaviour of specifier '%pD' is changed to print full path
> > of struct file, the related test cases are also updated.
> >
> > Given the string is prepended from the end of the buffer, the check
> > of "wrote beyond the nul-terminator" should be skipped.
>
> Sorry, that is far from enough justification.
>
> I should probably have split the "wrote beyond nul-terminator" check in two:
>
> One that checks whether any memory beyond the buffer given to
> vsnprintf() was touched (including all the padding, but possibly more
> for the cases where we pass a known-too-short buffer), symmetric to the
> "wrote before buffer" check.
>
> And then another that checks the area between the '\0' and the end of
> the given buffer - I suppose that it's fair game for vsnprintf to use
> all of that as scratch space, and for that it could be ok to add that
> boolean knob.
>
Sorry, I could have thought sth like "write beyond the buffer" had been checked by
old test cases, but seems not.
I will split the "wrote beyond nul-terminator" check into 2 parts. One for
Non-%pD case, the other for %pD.

For %pD, it needs to check whether the space beyond test_buffer[] is written

--
Cheers,
Justin (Jia He)

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