From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Subject: Re: fbcmap: non working tests on unsigned cmap->start Date: Sun, 26 Apr 2009 16:15:05 +0300 Message-ID: <20090426131505.GG7134@sci.fi> References: <49EDD799.8060607@gmail.com> <20090423134110.51ea8df2.akpm@linux-foundation.org> <20090423214738.GF7134@sci.fi> <49F4519F.4090003@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Received: from sfi-mx-1.v28.ch3.sourceforge.com ([172.29.28.121] helo=mx.sourceforge.net) by h25xhf1.ch3.sourceforge.com with esmtp (Exim 4.69) (envelope-from ) id 1Ly4CY-0003e9-0v for linux-fbdev-devel@lists.sourceforge.net; Sun, 26 Apr 2009 13:15:22 +0000 Received: from smtp6.welho.com ([213.243.153.40]) by 29vjzd1.ch3.sourceforge.com with esmtp (Exim 4.69) id 1Ly4CN-0006hD-OO for linux-fbdev-devel@lists.sourceforge.net; Sun, 26 Apr 2009 13:15:21 +0000 Content-Disposition: inline In-Reply-To: <49F4519F.4090003@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-fbdev-devel-bounces@lists.sourceforge.net To: Roel Kluin Cc: Andrew Morton , linux-fbdev-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, adaplas@gmail.com On Sun, Apr 26, 2009 at 02:20:47PM +0200, Roel Kluin wrote: > cmap->start is unsigned, A negative start could result in incorrect > colors. `start' is used as the starting index for the hardware palette, > 'start+len-1' is the last index. > = > Signed-off-by: Roel Kluin > --- > >>> vi include/linux/fb.h +478 > >>> > >>> Note that struct fb_cmap_user cmap->start in fb_set_user_cmap() is un= signed. > >>> Should there maybe be a test: > >>> > >>> if (cmap->start > MAX || ...) > >>> > >>> (and what should MAX be then?) > >>> > = > > On Thu, Apr 23, 2009 at 01:41:10PM -0700, Andrew Morton wrote: > >> argh. > >> > >> - Perhaps userspace can kill the kernel by sending a "negative" > >> `start'. Removing the test will make it even less likely that we'll > >> fix this bug. > > = > > Shouldn't happen. 'start' is used as the starting index for the hardware > > palette, 'start+len-1' is the last index. All drivers should already ch= eck > > the passed values since the maximum index depends on the display mode. > > And I suppose the worst thing that could happen if the driver fails to > > check the values would be incorrect colors. > = > Thanks for your explanation, I think this should fix it? > = > diff --git a/drivers/video/fbcmap.c b/drivers/video/fbcmap.c > index f53b9f1..ea62d87 100644 > --- a/drivers/video/fbcmap.c > +++ b/drivers/video/fbcmap.c > @@ -266,7 +266,7 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struc= t fb_info *info) > rc =3D -ENODEV; > goto out; > } > - if (cmap->start < 0 || (!info->fbops->fb_setcolreg && > + if (cmap->start >=3D cmap->len || (!info->fbops->fb_setcolreg && > !info->fbops->fb_setcmap)) { > rc =3D -EINVAL; > goto out1; That's not correct. There's nothing wrong with having 'start' >=3D 'len'. You would rather need something like 'if (start+len > 1 << max(red.len, green.len, blue.len, transp.len))' and a check to make sure that start+len doesn't overflow. Oh and I guess it should also check that the visual is pseudocolor or directcolor. -- = Ville Syrj=E4l=E4 syrjala@sci.fi http://www.sci.fi/~syrjala/ ---------------------------------------------------------------------------= --- Crystal Reports - New Free Runtime and 30 Day Trial Check out the new simplified licensign option that enables unlimited royalty-free distribution of the report engine for externally facing = server and web deployment. http://p.sf.net/sfu/businessobjects