On Fri, Mar 15, 2013 at 2:04 AM, Ric Mason <ric.masonn@xxxxxxxxx> wrote: > On 03/12/2013 07:57 AM, Luigi Semenzato wrote: >> >> Greetings linux-mmers, >> >> before we can fully deploy zram, we must ensure it conforms to the >> Chrome OS security requirements. In particular, we do not want to >> allow user space to read/write the swap device---not even root-owned >> processes. > > > Interesting. Thank you. >> >> A similar restriction is available for /dev/mem under >> CONFIG_STRICT_DEVMEM. > > > Sorry, what's /dev/mem used for? and why relevant your topic? I don't know what it's used for Chrome OS, but I don't think it matters. The point is that /dev/mem is compiled in the kernel, and without CONFIG_STRICT_DEVMEM it offers a way for a root-owned process to read/write all of physical memory. The situation is not as dire with a swap device, but currently a root-owned process can open a block device used for swap and peek and poke its data, which means that a root-owned process has now potential access to the data segment of any other process, among other things. >> >> There are a few possible approaches to this, but before we go ahead >> I'd like to ask if anything has happened or is planned in this >> direction. >> >> Otherwise, one idea I am playing with is to add a CONFIG_STRICT_SWAP >> option that would do this for any swap device (i.e. not specific to >> zram) and possibly also when swapping to a file. We would add an >> "internal" open flag, O_KERN_SWAP, as well as clean up a little bit >> the FMODE_NONOTIFY confusion by adding the kernel flag O_KERN_NONOTIFY >> and formalizing the sets of external (O_*) and internal (O_KERN_*) >> open flags. >> >> Swapon() and swapoff() would use O_KERN_SWAP internally, and a device >> opened with that flag would reject user-level opens. >> >> Thank you in advance for any input/suggestion! >> Luigi >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@xxxxxxxxx. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>