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-rw-r--r--fs/namespace.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 9786a38d1681..aabe8e397fc3 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3280,6 +3280,19 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
return !mnt_already_visible(ns, mnt, new_mnt_flags);
}
+bool mnt_may_suid(struct vfsmount *mnt)
+{
+ /*
+ * Foreign mounts (accessed via fchdir or through /proc
+ * symlinks) are always treated as if they are nosuid. This
+ * prevents namespaces from trusting potentially unsafe
+ * suid/sgid bits, file caps, or security labels that originate
+ * in other namespaces.
+ */
+ return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
+ current_in_userns(mnt->mnt_sb->s_user_ns);
+}
+
static struct ns_common *mntns_get(struct task_struct *task)
{
struct ns_common *ns = NULL;