Unverified Commit cefd55bd authored by Christian Brauner's avatar Christian Brauner
Browse files

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: default avatar <syzbot+0b2e79f91ff6579bfa5b@syzkaller.appspotmail.com>
Reported-by: default avatar <syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 18b5c400

include/linux/ns_common.h

+7 −4
Original line number Diff line number Diff line
@@ -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)

include/linux/nsproxy.h

+2 −2
Original line number Diff line number Diff line
@@ -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)

kernel/nsproxy.c

+20 −16
Original line number Diff line number Diff line
@@ -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)