From cefd55bd2159f427228d44864747243946296739 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Tue, 11 Nov 2025 22:29:44 +0100 Subject: [PATCH] nsproxy: fix free_nsproxy() and simplify create_new_namespaces() Make it possible to handle NULL being passed to the reference count helpers instead of forcing the caller to handle this. Afterwards we can nicely allow a cleanup guard to handle nsproxy freeing. Active reference count handling is not done in nsproxy_free() but rather in free_nsproxy() as nsproxy_free() is also called from setns() failure paths where a new nsproxy has been prepared but has not been marked as active via switch_task_namespaces(). Link: https://lore.kernel.org/690bfb9e.050a0220.2e3c35.0013.GAE@google.com Link: https://patch.msgid.link/20251111-sakralbau-guthaben-7dcc277d337f@brauner Fixes: 3c9820d5c64a ("ns: add active reference count") Reported-by: syzbot+0b2e79f91ff6579bfa5b@syzkaller.appspotmail.com Reported-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com Signed-off-by: Christian Brauner --- include/linux/ns_common.h | 11 +++++++---- include/linux/nsproxy.h | 4 ++-- kernel/nsproxy.c | 36 ++++++++++++++++++++---------------- 3 files changed, 29 insertions(+), 22 deletions(-) diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h index 136f6a322e53..825f5865bfc5 100644 --- a/include/linux/ns_common.h +++ b/include/linux/ns_common.h @@ -114,11 +114,14 @@ static __always_inline __must_check bool __ns_ref_dec_and_lock(struct ns_common } #define ns_ref_read(__ns) __ns_ref_read(to_ns_common((__ns))) -#define ns_ref_inc(__ns) __ns_ref_inc(to_ns_common((__ns))) -#define ns_ref_get(__ns) __ns_ref_get(to_ns_common((__ns))) -#define ns_ref_put(__ns) __ns_ref_put(to_ns_common((__ns))) +#define ns_ref_inc(__ns) \ + do { if (__ns) __ns_ref_inc(to_ns_common((__ns))); } while (0) +#define ns_ref_get(__ns) \ + ((__ns) ? __ns_ref_get(to_ns_common((__ns))) : false) +#define ns_ref_put(__ns) \ + ((__ns) ? __ns_ref_put(to_ns_common((__ns))) : false) #define ns_ref_put_and_lock(__ns, __ns_lock) \ - __ns_ref_dec_and_lock(to_ns_common((__ns)), __ns_lock) + ((__ns) ? __ns_ref_dec_and_lock(to_ns_common((__ns)), __ns_lock) : false) #define ns_ref_active_read(__ns) \ ((__ns) ? __ns_ref_active_read(to_ns_common(__ns)) : 0) diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h index ac825eddec59..5a67648721c7 100644 --- a/include/linux/nsproxy.h +++ b/include/linux/nsproxy.h @@ -99,7 +99,7 @@ void get_cred_namespaces(struct task_struct *tsk); void exit_cred_namespaces(struct task_struct *tsk); void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new); int exec_task_namespaces(void); -void free_nsproxy(struct nsproxy *ns); +void deactivate_nsproxy(struct nsproxy *ns); int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **, struct cred *, struct fs_struct *); int __init nsproxy_cache_init(void); @@ -107,7 +107,7 @@ int __init nsproxy_cache_init(void); static inline void put_nsproxy(struct nsproxy *ns) { if (refcount_dec_and_test(&ns->count)) - free_nsproxy(ns); + deactivate_nsproxy(ns); } static inline void get_nsproxy(struct nsproxy *ns) diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c index 94c2cfe0afa1..259c4b4f1eeb 100644 --- a/kernel/nsproxy.c +++ b/kernel/nsproxy.c @@ -60,6 +60,25 @@ static inline struct nsproxy *create_nsproxy(void) return nsproxy; } +static inline void nsproxy_free(struct nsproxy *ns) +{ + put_mnt_ns(ns->mnt_ns); + put_uts_ns(ns->uts_ns); + put_ipc_ns(ns->ipc_ns); + put_pid_ns(ns->pid_ns_for_children); + put_time_ns(ns->time_ns); + put_time_ns(ns->time_ns_for_children); + put_cgroup_ns(ns->cgroup_ns); + put_net(ns->net_ns); + kmem_cache_free(nsproxy_cachep, ns); +} + +void deactivate_nsproxy(struct nsproxy *ns) +{ + nsproxy_ns_active_put(ns); + nsproxy_free(ns); +} + /* * Create new nsproxy and all of its the associated namespaces. * Return the newly created nsproxy. Do not attach this to the task, @@ -185,21 +204,6 @@ int copy_namespaces(u64 flags, struct task_struct *tsk) return 0; } -void free_nsproxy(struct nsproxy *ns) -{ - nsproxy_ns_active_put(ns); - - put_mnt_ns(ns->mnt_ns); - put_uts_ns(ns->uts_ns); - put_ipc_ns(ns->ipc_ns); - put_pid_ns(ns->pid_ns_for_children); - put_time_ns(ns->time_ns); - put_time_ns(ns->time_ns_for_children); - put_cgroup_ns(ns->cgroup_ns); - put_net(ns->net_ns); - kmem_cache_free(nsproxy_cachep, ns); -} - /* * Called from unshare. Unshare all the namespaces part of nsproxy. * On success, returns the new nsproxy. @@ -338,7 +342,7 @@ static void put_nsset(struct nsset *nsset) if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) free_fs_struct(nsset->fs); if (nsset->nsproxy) - free_nsproxy(nsset->nsproxy); + nsproxy_free(nsset->nsproxy); } static int prepare_nsset(unsigned flags, struct nsset *nsset) -- 2.47.3