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: ellyjo...@chromium.org
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
drivers/base/devtmpfs.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
