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60e6a983e5
Assign a unique proc inode to each namespace, and use that
inode number to ensure we only allocate at most one proc
inode for every namespace in proc.
A single proc inode per namespace allows userspace to test
to see if two processes are in the same namespace.
This has been a long requested feature and only blocked because
a naive implementation would put the id in a global space and
would ultimately require having a namespace for the names of
namespaces, making migration and certain virtualization tricks
impossible.
We still don't have per superblock inode numbers for proc, which
appears necessary for application unaware checkpoint/restart and
migrations (if the application is using namespace file descriptors)
but that is now allowd by the design if it becomes important.
I have preallocated the ipc and uts initial proc inode numbers so
their structures can be statically initialized.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
(cherry picked from commit 98f842e675)
72 lines
1.5 KiB
C
72 lines
1.5 KiB
C
#ifndef _LINUX_USER_NAMESPACE_H
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#define _LINUX_USER_NAMESPACE_H
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#include <linux/kref.h>
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#include <linux/nsproxy.h>
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#include <linux/sched.h>
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#include <linux/err.h>
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#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
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#define UIDHASH_SZ (1 << UIDHASH_BITS)
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struct user_namespace {
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struct kref kref;
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struct hlist_head uidhash_table[UIDHASH_SZ];
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struct user_struct *creator;
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struct work_struct destroyer;
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unsigned int proc_inum;
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};
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extern struct user_namespace init_user_ns;
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#ifdef CONFIG_USER_NS
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static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
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{
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if (ns)
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kref_get(&ns->kref);
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return ns;
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}
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extern int create_user_ns(struct cred *new);
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extern void free_user_ns(struct kref *kref);
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static inline void put_user_ns(struct user_namespace *ns)
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{
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if (ns)
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kref_put(&ns->kref, free_user_ns);
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}
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uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid);
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gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid);
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#else
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static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
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{
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return &init_user_ns;
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}
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static inline int create_user_ns(struct cred *new)
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{
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return -EINVAL;
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}
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static inline void put_user_ns(struct user_namespace *ns)
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{
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}
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static inline uid_t user_ns_map_uid(struct user_namespace *to,
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const struct cred *cred, uid_t uid)
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{
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return uid;
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}
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static inline gid_t user_ns_map_gid(struct user_namespace *to,
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const struct cred *cred, gid_t gid)
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{
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return gid;
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}
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#endif
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#endif /* _LINUX_USER_H */
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