linux-kernel - Re: [PATCH][serial-next] serial: 8250: don't dereference em485 until it has been null checked

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Date:   Tue, 29 Aug 2017 23:22:04 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Colin King <colin.king@...onical.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Phil Elwell <phil@...pberrypi.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Eric Anholt <eric@...olt.net>,
        Thor Thayer <tthayer@...nsource.altera.com>,
        Rafael Gago <rafael.gago@...il.com>,
        David Lechner <david@...hnology.com>,
        linux-serial@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][serial-next] serial: 8250: don't dereference em485
 until it has been null checked

On Tue, 2017-08-29 at 23:04 +0300, Dan Carpenter wrote:
> On Tue, Aug 29, 2017 at 05:58:15PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > Currently, the pointer em485 is dereferenced to get p and then later
> > em485 is checked to see if it is null before calling __start_tx. In
> > the case where em485 is null, we get a null pointer dereference. Fix
> > this by moving the deference and the associated spinlock/unlocks on
> > p to the code block where em485 is known to be not null.
> > 
> > Detected by CoverityScan, CID#14555001 ("Dereference before null
> > check")
> > 
> > Fixes 6e0a5de2136b ("serial: 8250: Use hrtimers for rs485 delays")
> 
> I don't understand which tree this commit is from.  I have it fetched
> but when I do a git log on drivers/tty/serial/8250/8250_port.c then I
> don't see it.  I have today's linux-next.

I see it, though I have tty-next as well.


> I'm pretty sure "t" isn't ever NULL.

(I'm pretty sure there is a false positive, though code would be cleaned
to avoid such reports)

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy