[PATCH 6/8] ns: add asserts for active refcount underflow
From: Christian Brauner <brauner@kernel.org>
Date: 2025-11-09 21:13:48
Also in:
bpf, cgroups, linux-fsdevel, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
Add a few more assert to detect active reference count underflows. Signed-off-by: Christian Brauner <brauner@kernel.org> --- include/linux/ns_common.h | 1 - kernel/nscommon.c | 18 ++++++++++++++---- 2 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index 3aaba2ca31d7..66ea09b48377 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h@@ -294,7 +294,6 @@ void __ns_ref_active_put(struct ns_common *ns); static __always_inline struct ns_common *__must_check ns_get_unless_inactive(struct ns_common *ns) { - VFS_WARN_ON_ONCE(__ns_ref_active_read(ns) && !__ns_ref_read(ns)); if (!__ns_ref_active_read(ns)) { VFS_WARN_ON_ONCE(is_ns_init_id(ns)); return NULL;
diff --git a/kernel/nscommon.c b/kernel/nscommon.c
index bfd2d6805776..c910b979e433 100644
--- a/kernel/nscommon.c
+++ b/kernel/nscommon.c@@ -170,8 +170,10 @@ void __ns_ref_active_put(struct ns_common *ns) if (is_ns_init_id(ns)) return; - if (!atomic_dec_and_test(&ns->__ns_ref_active)) + if (!atomic_dec_and_test(&ns->__ns_ref_active)) { + VFS_WARN_ON_ONCE(__ns_ref_active_read(ns) < 0); return; + } VFS_WARN_ON_ONCE(is_ns_init_id(ns)); VFS_WARN_ON_ONCE(!__ns_ref_read(ns));
@@ -181,8 +183,10 @@ void __ns_ref_active_put(struct ns_common *ns) if (!ns) return; VFS_WARN_ON_ONCE(is_ns_init_id(ns)); - if (!atomic_dec_and_test(&ns->__ns_ref_active)) + if (!atomic_dec_and_test(&ns->__ns_ref_active)) { + VFS_WARN_ON_ONCE(__ns_ref_active_read(ns) < 0); return; + } } }
@@ -280,12 +284,16 @@ void __ns_ref_active_put(struct ns_common *ns) */ void __ns_ref_active_get(struct ns_common *ns) { + int prev; + /* Initial namespaces are always active. */ if (is_ns_init_id(ns)) return; /* If we didn't resurrect the namespace we're done. */ - if (atomic_fetch_add(1, &ns->__ns_ref_active)) + prev = atomic_fetch_add(1, &ns->__ns_ref_active); + VFS_WARN_ON_ONCE(prev < 0); + if (likely(prev)) return; /*
@@ -298,7 +306,9 @@ void __ns_ref_active_get(struct ns_common *ns) return; VFS_WARN_ON_ONCE(is_ns_init_id(ns)); - if (atomic_fetch_add(1, &ns->__ns_ref_active)) + prev = atomic_fetch_add(1, &ns->__ns_ref_active); + VFS_WARN_ON_ONCE(prev < 0); + if (likely(prev)) return; } }
--
2.47.3