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Cache user_ns in struct cred 

If !CONFIG_USERNS, have current_user_ns() defined to (&init_user_ns).

Get rid of _current_user_ns.  This requires nsown_capable() to be
defined in capability.c rather than as static inline in capability.h,
so do that.

Request_key needs init_user_ns defined at current_user_ns if
!CONFIG_USERNS, so forward-declare that in cred.h if !CONFIG_USERNS
at current_user_ns() define.

Compile-tested with and without CONFIG_USERNS.

Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
[ This makes a huge performance difference for acl_permission_check(),
  up to 30%.  And that is one of the hottest kernel functions for loads
  that are pathname-lookup heavy.  ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Serge E. Hallyn 2011-05-13 04:27:54 +01:00 committed by Linus Torvalds
parent 381e7863d9
commit 47a150edc2
4 changed files with 27 additions and 20 deletions
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13
include/linux/capability.h
View File

@ -546,18 +546,7 @@ extern bool has_capability_noaudit(struct task_struct *t, int cap);
extern bool capable(int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
extern bool task_ns_capable(struct task_struct *t, int cap);
/**
* nsown_capable - Check superior capability to one's own user_ns
* @cap: The capability in question
*
* Return true if the current task has the given superior capability
* targeted at its own user namespace.
*/
static inline bool nsown_capable(int cap)
{
return ns_capable(current_user_ns(), cap);
}
extern bool nsown_capable(int cap);
/* audit system wants to get cap info from files as well */
extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);

10
include/linux/cred.h
View File

@ -146,6 +146,7 @@ struct cred {
void *security; /* subjective LSM security */
#endif
struct user_struct *user; /* real user ID subscription */
struct user_namespace *user_ns; /* cached user->user_ns */
struct group_info *group_info; /* supplementary groups for euid/fsgid */
struct rcu_head rcu; /* RCU deletion hook */
};
@ -354,10 +355,15 @@ static inline void put_cred(const struct cred *_cred)
#define current_fsgid() (current_cred_xxx(fsgid))
#define current_cap() (current_cred_xxx(cap_effective))
#define current_user() (current_cred_xxx(user))
#define _current_user_ns() (current_cred_xxx(user)->user_ns)
#define current_security() (current_cred_xxx(security))
extern struct user_namespace *current_user_ns(void);
#ifdef CONFIG_USER_NS
#define current_user_ns() (current_cred_xxx(user_ns))
#else
extern struct user_namespace init_user_ns;
#define current_user_ns() (&init_user_ns)
#endif
#define current_uid_gid(_uid, _gid) \
do { \

12
kernel/capability.c
View File

@ -399,3 +399,15 @@ bool task_ns_capable(struct task_struct *t, int cap)
return ns_capable(task_cred_xxx(t, user)->user_ns, cap);
}
EXPORT_SYMBOL(task_ns_capable);
/**
* nsown_capable - Check superior capability to one's own user_ns
* @cap: The capability in question
*
* Return true if the current task has the given superior capability
* targeted at its own user namespace.
*/
bool nsown_capable(int cap)
{
return ns_capable(current_user_ns(), cap);
}

12
kernel/cred.c
View File

@ -54,6 +54,7 @@ struct cred init_cred = {
.cap_effective = CAP_INIT_EFF_SET,
.cap_bset = CAP_INIT_BSET,
.user = INIT_USER,
.user_ns = &init_user_ns,
.group_info = &init_groups,
#ifdef CONFIG_KEYS
.tgcred = &init_tgcred,
@ -410,6 +411,11 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
goto error_put;
}
/* cache user_ns in cred. Doesn't need a refcount because it will
* stay pinned by cred->user
*/
new->user_ns = new->user->user_ns;
#ifdef CONFIG_KEYS
/* new threads get their own thread keyrings if their parent already
* had one */
@ -741,12 +747,6 @@ int set_create_files_as(struct cred *new, struct inode *inode)
}
EXPORT_SYMBOL(set_create_files_as);
struct user_namespace *current_user_ns(void)
{
return _current_user_ns();
}
EXPORT_SYMBOL(current_user_ns);
#ifdef CONFIG_DEBUG_CREDENTIALS
bool creds_are_invalid(const struct cred *cred)