Date: Thu, 14 Nov 2013 16:25:39 +0300 From: Dan Carpenter <dan.carpenter@...cle.com> To: Nico Golde <oss-security+ml@...lde.de>, oss-security@...ts.openwall.com, security@...nel.org, "Hans J. Koch" <hjk@...sjkoch.de> Subject: Re: some unstracked linux kernel security fixes On Thu, Nov 14, 2013 at 11:33:10AM +0100, Petr Matousek wrote: > On Tue, Nov 12, 2013 at 11:10:32AM +0100, Petr Matousek wrote: > > Hi, > > > > On Sun, Nov 03, 2013 at 05:32:52PM +0100, Nico Golde wrote: > > > drivers/uio/uio.c: mapping of physical memory to user space without proper size check > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7314e613d5ff > > > > there is a size check in uio_mmap() (the only caller of uio_mmap_physical()): > > > > requested_pages = vma_pages(vma); > > actual_pages = ((idev->info->mem[mi].addr & ~PAGE_MASK) > > + idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT; > > if (requested_pages > actual_pages) > > return -EINVAL; > > > > why it wasn't sufficient? > > Apparently there was a CVE split  and this is now CVE-2013-6763. > > http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-6763 > > I still think this is a non-issue based on the above mentioned size > check. Can I please get second opinion from someone more knowledgeable > on this? > > Added Hans to the CC list since he's the maintainer. Petr is asking if the size checks in uio_mmap() and uio_mmap_physical() are duplicative. > Isn't the size check redundant because of > > requested_pages = vma_pages(vma); > actual_pages = ((idev->info->mem[mi].addr & ~PAGE_MASK) > + idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT; > if (requested_pages > actual_pages) > return -EINVAL; That check is worrying requested_pages is rounded down to the nearest page but actual_pages is rounded up. I don't understand why we are adding "(mem[mi]addr % PAGE_SIZE)" to the pre rounded up actual_pages. So, yeah, it seems like we do check the size twice now except the first time we do it wrong. regards, dan carpenter
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