fs: relax permissions for listmount()

It is sufficient to have capabilities in the owning user namespace of
the mount namespace to list all mounts regardless of whether they are
reachable or not.

Link: https://lore.kernel.org/r/8adc0d3f4f7495faacc6a7c63095961f7f1637c7.1719243756.git.josef@toxicpanda.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 02a697287da5466818af9348ccfd767ff0427952..22274f74beb0ed37bdfb723d0229cc11bf95bc23 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5104,7 +5104,7 @@ static ssize_t do_listmount(u64 mnt_parent_id, u64 last_mnt_id, u64 *mnt_ids,
         * mounts to show users.
         */
        if (!is_path_reachable(real_mount(orig.mnt), orig.dentry, &root) &&
-           !ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN))
+           !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
                return -EPERM;
 
        ret = security_sb_statfs(orig.dentry);