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

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Date:   Tue, 15 Jun 2021 07:06:03 +0000
From:   Justin He <Justin.He@....com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
CC:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH RFCv3 3/3] lib/test_printf: add test cases for '%pD'

Hi Rasmus

> -----Original Message-----
> From: Rasmus Villemoes <linux@...musvillemoes.dk>
> Sent: Saturday, June 12, 2021 5:40 AM
> To: Justin He <Justin.He@....com>; Petr Mladek <pmladek@...e.com>; Steven
> Rostedt <rostedt@...dmis.org>; Sergey Senozhatsky
> <senozhatsky@...omium.org>; Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com>; Jonathan Corbet <corbet@....net>;
> Alexander Viro <viro@...iv.linux.org.uk>; Linus Torvalds <torvalds@...ux-
> foundation.org>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>; Eric Biggers
> <ebiggers@...gle.com>; Ahmed S. Darwish <a.darwish@...utronix.de>; linux-
> doc@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> fsdevel@...r.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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