do_add_mount() should sanitize mnt_flags

MNT_WRITE_HOLD shouldn't leak into new vfsmount and neither
should MNT_SHARED (the latter will be set properly, along with
the rest of shared-subtree data structures)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 779293e29b85..c768f733c8d6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1671,6 +1671,8 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path,
 {
         int err;
 
+        mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD);
+
         down_write(&namespace_sem);
         /* Something was mounted here while we slept */
         while (d_mountpoint(path->dentry) &&