lkml.org 
[lkml]   [2012]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] devtmpfs: mount with noexec and nosuid
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?

thanks,

greg k-h

>
> diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
> index 147d1a4..b7e2e57 100644
> --- a/drivers/base/devtmpfs.c
> +++ b/drivers/base/devtmpfs.c
> @@ -340,6 +340,7 @@ static int handle_remove(const char *nodename, struct device *dev)
> int devtmpfs_mount(const char *mntdir)
> {
> int err;
> + int mflags = MS_SILENT | MS_NOEXEC | MS_NOSUID;
>
> if (!mount_dev)
> return 0;
> @@ -347,7 +348,7 @@ int devtmpfs_mount(const char *mntdir)
> if (!thread)
> return 0;
>
> - err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
> + err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", mflags, NULL);
> if (err)
> printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
> else
> @@ -368,11 +369,12 @@ static int handle(const char *name, umode_t mode, struct device *dev)
> static int devtmpfsd(void *p)
> {
> char options[] = "mode=0755";
> + int mflags = MS_SILENT | MS_NOEXEC | MS_NOSUID;
> int *err = p;
> *err = sys_unshare(CLONE_NEWNS);
> if (*err)
> goto out;
> - *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
> + *err = sys_mount("devtmpfs", "/", "devtmpfs", mflags, options);
> if (*err)
> goto out;
> sys_chdir("/.."); /* will traverse into overmounted root */
> --
> 1.7.9.5
>
>
> --
> Kees Cook
> Chrome OS Security


\
 
 \ /
  Last update: 2012-11-17 03:01    [W:0.056 / U:0.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site