[PATCH] fs/namespace: correctly handle errors returned by grab_requested_mnt_ns

Andrei Vagin
2025-11-11T06:28:32Z

grab_requested_mnt_ns was changed to return error codes on failure, but
its callers were not updated to check for error pointers, still checking
only for a NULL return value.

This commit updates the callers to use IS_ERR() or IS_ERR_OR_NULL() and
PTR_ERR() to correctly check for and propagate errors.

Fixes: 7b9d14af8777 ("fs: allow mount namespace fd")
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrei Vagin <avagin@google.com>
---
fs/namespace.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index d82910f33dc4..9124465dca55 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -144,8 +144,10 @@ static inline struct mnt_namespace *node_to_mnt_ns(const struct rb_node *node)

static void mnt_ns_release(struct mnt_namespace *ns)
{
+ if (IS_ERR_OR_NULL(ns))
+ return;
/* keep alive for {list,stat}mount() */
- if (ns && refcount_dec_and_test(&ns->passive)) {
+ if (refcount_dec_and_test(&ns->passive)) {
fsnotify_mntns_delete(ns);
put_user_ns(ns->user_ns);
kfree(ns);
@@ -5756,8 +5758,10 @@ static struct mnt_namespace *grab_requested_mnt_ns(const struct mnt_id_req *kreq
if (kreq->mnt_ns_id && kreq->spare)
return ERR_PTR(-EINVAL);

- if (kreq->mnt_ns_id)
- return lookup_mnt_ns(kreq->mnt_ns_id);
+ if (kreq->mnt_ns_id) {
+ mnt_ns = lookup_mnt_ns(kreq->mnt_ns_id);
+ return mnt_ns ? : ERR_PTR(-ENOENT);
+ }

if (kreq->spare) {
struct ns_common *ns;
@@ -5801,8 +5805,8 @@ SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,
return ret;

ns = grab_requested_mnt_ns(&kreq);
- if (!ns)
- return -ENOENT;
+ if (IS_ERR(ns))
+ return PTR_ERR(ns);

if (kreq.mnt_ns_id && (ns != current->nsproxy->mnt_ns) &&
!ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
@@ -5912,8 +5916,8 @@ static void __free_klistmount_free(const struct klistmount *kls)
static inline int prepare_klistmount(struct klistmount *kls, struct mnt_id_req *kreq,
size_t nr_mnt_ids)
{
-
u64 last_mnt_id = kreq->param;
+ struct mnt_namespace *ns;

/* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */
if (last_mnt_id != 0 && last_mnt_id <= MNT_UNIQUE_ID_OFFSET)
@@ -5927,9 +5931,10 @@ static inline int prepare_klistmount(struct klistmount *kls, struct mnt_id_req *
if (!kls->kmnt_ids)
return -ENOMEM;

- kls->ns = grab_requested_mnt_ns(kreq);
- if (!kls->ns)
- return -ENOENT;
+ ns = grab_requested_mnt_ns(kreq);
+ if (IS_ERR(ns))
+ return PTR_ERR(ns);
+ kls->ns = ns;

kls->mnt_parent_id = kreq->mnt_id;
return 0;
--
2.51.2.1041.gc1ab5b90ca-goog