vfs: open() with O_CREAT should not create inodes with unknown ids

may_create() rejects creation of inodes with ids which lack a
mapping into s_user_ns. However for O_CREAT may_o_create() is
is used instead. Add a similar check there.

Fixes: 036d523641c6 ("vfs: Don't create inodes with a uid or gid unknown to the vfs")
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/namei.c b/fs/namei.c
index ad74877e1442..6fa3e9138fe4 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2941,10 +2941,16 @@ static inline int open_to_namei_flags(int flag)
 
 static int may_o_create(const struct path *dir, struct dentry *dentry, umode_t mode)
 {
+        struct user_namespace *s_user_ns;
         int error = security_path_mknod(dir, dentry, mode, 0);
         if (error)
                 return error;
 
+        s_user_ns = dir->dentry->d_sb->s_user_ns;
+        if (!kuid_has_mapping(s_user_ns, current_fsuid()) ||
+            !kgid_has_mapping(s_user_ns, current_fsgid()))
+                return -EOVERFLOW;
+
         error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
         if (error)
                 return error;