Messages in this thread | | | Date | Mon, 19 Nov 2012 10:14:46 -0800 | Subject | Re: [PATCH] devtmpfs: mount with noexec and nosuid | From | Kees Cook <> |
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On Fri, Nov 16, 2012 at 4:39 PM, Kay Sievers <kay@vrfy.org> wrote: > On Sat, Nov 17, 2012 at 1:27 AM, Greg Kroah-Hartman > <gregkh@linuxfoundation.org> wrote: >> On Fri, Nov 16, 2012 at 04:20:16PM -0800, Kees Cook wrote: >>> Since devtmpfs is writable, make the default noexec nosuid as well. This >>> protects from the case of a privileged process having an arbitrary file >>> write flaw and an argumentless arbitrary execution (i.e. it would lack >>> the ability to run "mount -o remount,exec,suid /dev"), with a system >>> that already has nosuid,noexec on all other writable mounts. >>> >>> Cc: ellyjones@chromium.org >>> Signed-off-by: Kees Cook <keescook@chromium.org> >>> --- >>> drivers/base/devtmpfs.c | 6 ++++-- >>> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> Have you tested this to verify that it doesn't break anything? >> >> Kay, could this cause any problems that you could think of? > > It breaks all sorts of old, possibly outdated, stuff, that does things > like mapping /dev/mem executable. It for sure used to break X drivers, > that fiddle with the BIOS of cards.
Ah, yeah, you're totally right. Attempting an mmap with PROT_EXEC on /dev/mem would be denied.
Is this something we could put behind a CONFIG?
-Kees
-- Kees Cook Chrome OS Security
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