linux-kernel - Re: [PATCH 1/2] staging: iio replaced kmalloc with local variables.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 06 Jun 2011 15:49:17 -0700
From:	Joe Perches <joe@...ches.com>
To:	Greg KH <gregkh@...e.de>
Cc:	anish <anish198519851985@...il.com>, devel@...verdev.osuosl.org,
	arnd@...db.de, lucas.demarchi@...fusion.mobi,
	linux-kernel@...r.kernel.org, jic23@....ac.uk,
	manuel.stahl@....fraunhofer.de
Subject: Re: [PATCH 1/2] staging: iio replaced kmalloc with local variables.

On Mon, 2011-06-06 at 15:41 -0700, Greg KH wrote:
> On Mon, Jun 06, 2011 at 03:28:29PM -0700, Joe Perches wrote:
> > On Mon, 2011-06-06 at 15:21 -0700, Greg KH wrote:
> > > On Mon, Jun 06, 2011 at 03:10:57PM -0700, Joe Perches wrote:
> > > > On Mon, 2011-06-06 at 14:55 -0700, Greg KH wrote:
> > > > > On Tue, Jun 07, 2011 at 12:37:37AM +0530, anish wrote:
> > > > > > From: anish kumar <anish198519851985@...il.com>
> > > > > > Replace kmalloc with local variables as it was un-necessary and
> > > > > > also removed the redudant code after this change.
> > > > > SPI data, like USB data, has to come from kmalloced data, not from the
> > > > > stack, or bad things can, and will, happen.
> > > > Perhaps just add a comment like:
> > > > +       u8 *tx = kmalloc(2, GFP_KERNEL);	/* can't be on stack */
> > > You really want to do to that for _EVERY_ SPI and USB driver?  I don't
> > > think so.
> > Nope, only the ones that look especially odd because 
> > 	kmalloc(sizeof(struct foo), ...)
> > or
> > 	kmalloc(sizeof("type), ...)
> > is not used.
> > It might be better to just declare a 2 byte struct.
> No, this is a very common thing for all USB and SPI drivers.  It's so
> obvious that once I saw the Subject: line, I knew this patch was going
> to be wrong.

As did I.
I seek to find a way to avoid seeing them in the future too.

> This is something that the USB and SPI developers know all about, it's
> the way things work, and this driver works, so why are people trying to
> "clean" it up in ways that will break it, or cause extra work with
> structures where they are not needed at all?
> odd.

Because people perform pattern recognition as a means to avoid
the work required for complete understanding.

Comments akin to the one in drivers/usb/serial/io_ti.c:

	lsr = kmalloc(1, GFP_KERNEL);	/* Sigh, that's right, just one byte,
					   as not all platforms can do DMA
					   from stack */

help people avoid applying patterns to inappropriate uses.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/