linux-kernel - Re: [PATCH v7 00/10] vsprintf: Prevent silent crashes and consolidate error handling

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Message-ID: <20190426130204.GS9224@smile.fi.intel.com>
Date:   Fri, 26 Apr 2019 16:02:04 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Tobin C . Harding" <me@...in.cc>, Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 00/10] vsprintf: Prevent silent crashes and
 consolidate error handling

On Wed, Apr 24, 2019 at 03:53:06PM +0200, Petr Mladek wrote:
> On Fri 2019-04-19 10:51:12, Sergey Senozhatsky wrote:
> > On (04/17/19 13:53), Petr Mladek wrote:
> > > Crash in vsprintf() might be silent when it happens under logbuf_lock
> > > in vprintk_emit(). This patch set prevents most of the crashes by probing
> > > the address. The check is done only by %s and some %p* specifiers that need
> > > to dereference the address.
> > >
> > > Only the first byte of the address is checked to keep it simple. It should
> > > be enough to catch most problems.
> > >
> > > The check is explicitly done in each function that does the dereference.
> > > It helps to avoid the questionable strchr() of affected specifiers. This
> > > change motivated me to do some preparation patches that consolidated
> > > the error handling and cleaned the code a bit.
> > 
> > The patch set looks OK to me.
> > 
> > I got confused by 'pC?' error string, but once you start looking
> > at it as a regex (? - zero or one occurrences) things look OK.
> > Regex in dmesg/serial output might be something very new to people,
> > stack traces, after all, is a rather common error reporting mechanism.
> > So the previous "WARN_ON() + exact unrecognized fmt[N] char" was not
> > totally awful or wrong (well, it was, before we introduced printk_safe()),
> > but I don't have strong objections against that new regex thing.
> > 
> > FWIW,
> > Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> 
> Thanks a lot for review.
> 
> I have pushed the entire patchset into printk.git,
> branch for-5.2-vsprintf-hardening to get some
> test coverage via linux-next.
> 
> I still expect some feedback, especially from Andy
> who seems to have a vacation these days.
> I think that Andy wanted these changes rather sooner
> than later, so I hope that he would be fine with it.
> I could take it back in case of disagreement.

They are good enough to me, thanks!
FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko