1 files changed, 10 insertions, 1 deletions

diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index a7934ac75e5b..5f9e689dc8f0 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -153,10 +153,19 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
                         goto err_unlock;
                 ret = -EPERM;
                 pcred = __task_cred(p);
+                /* If victim is in different user_ns, then uids are not
+                   comparable, so we must have CAP_SYS_PTRACE */
+                if (cred->user->user_ns != pcred->user->user_ns) {
+                        if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
+                                goto err_unlock;
+                        goto ok;
+                }
+                /* If victim is in same user_ns, then uids are comparable */
                 if (cred->euid != pcred->euid &&
                     cred->euid != pcred->uid &&
-                    !capable(CAP_SYS_PTRACE))
+                    !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
                         goto err_unlock;
+ok:
                 head = p->compat_robust_list;
                 rcu_read_unlock();
         }