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userns: Make the count of user namespaces per user

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Add a structure that is per user and per user ns and use it to hold
the count of user namespaces.  This makes prevents one user from
creating denying service to another user by creating the maximum
number of user namespaces.

Rename the sysctl export of the maximum count from
/proc/sys/userns/max_user_namespaces to /proc/sys/user/max_user_namespaces
to reflect that the count is now per user.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-08-08 13:54:50 -05:00
parent b376c3e1b6
commit f6b2db1a3e
4 changed files with 117 additions and 30 deletions
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18
include/linux/user_namespace.h
View file

@ -22,6 +22,7 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
struct ucounts;
struct user_namespace {
struct uid_gid_map uid_map;
struct uid_gid_map gid_map;
@ -44,15 +45,24 @@ struct user_namespace {
struct ctl_table_set set;
struct ctl_table_header *sysctls;
#endif
struct ucounts *ucounts;
int max_user_namespaces;
};
struct ucounts {
struct hlist_node node;
struct user_namespace *ns;
kuid_t uid;
atomic_t count;
atomic_t user_namespaces;
};
extern struct user_namespace init_user_ns;
extern bool setup_userns_sysctls(struct user_namespace *ns);
extern void retire_userns_sysctls(struct user_namespace *ns);
extern bool inc_user_namespaces(struct user_namespace *ns);
extern void dec_user_namespaces(struct user_namespace *ns);
bool setup_userns_sysctls(struct user_namespace *ns);
void retire_userns_sysctls(struct user_namespace *ns);
struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid);
void dec_user_namespaces(struct ucounts *ucounts);
#ifdef CONFIG_USER_NS