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Commit 98f368e9 authored by Tyler Hicks's avatar Tyler Hicks Committed by James Morris
Browse files

kernel: Add noaudit variant of ns_capable() 



When checking the current cred for a capability in a specific user
namespace, it isn't always desirable to have the LSMs audit the check.
This patch adds a noaudit variant of ns_capable() for when those
situations arise.

The common logic between ns_capable() and the new ns_capable_noaudit()
is moved into a single, shared function to keep duplicated code to a
minimum and ease maintainability.

Signed-off-by: default avatarTyler Hicks <tyhicks@canonical.com>
Acked-by: default avatarSerge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: default avatarJames Morris <james.l.morris@oracle.com>
parent 2885c1e3

include/linux/capability.h

+5 −0
Original line number Diff line number Diff line
@@ -206,6 +206,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t, 
				      struct user_namespace *ns, int cap);

extern bool capable(int cap);

extern bool ns_capable(struct user_namespace *ns, int cap);

extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);

#else

static inline bool has_capability(struct task_struct *t, int cap)

{
@@ -233,6 +234,10 @@ static inline bool ns_capable(struct user_namespace *ns, int cap) 
{

	return true;

}

static inline bool ns_capable_noaudit(struct user_namespace *ns, int cap)

{

	return true;

}

#endif /* CONFIG_MULTIUSER */

extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);

extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);

kernel/capability.c

+36 −10
Original line number Diff line number Diff line
@@ -361,6 +361,24 @@ bool has_capability_noaudit(struct task_struct *t, int cap) 
	return has_ns_capability_noaudit(t, &init_user_ns, cap);

}



static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)

{

	int capable;



	if (unlikely(!cap_valid(cap))) {

		pr_crit("capable() called with invalid cap=%u\n", cap);

		BUG();

	}



	capable = audit ? security_capable(current_cred(), ns, cap) :

			  security_capable_noaudit(current_cred(), ns, cap);

	if (capable == 0) {

		current->flags |= PF_SUPERPRIV;

		return true;

	}

	return false;

}



/**

 * ns_capable - Determine if the current task has a superior capability in effect

 * @ns:  The usernamespace we want the capability in
@@ -374,19 +392,27 @@ bool has_capability_noaudit(struct task_struct *t, int cap) 
 */

bool ns_capable(struct user_namespace *ns, int cap)

{

	if (unlikely(!cap_valid(cap))) {

		pr_crit("capable() called with invalid cap=%u\n", cap);

		BUG();

	}



	if (security_capable(current_cred(), ns, cap) == 0) {

		current->flags |= PF_SUPERPRIV;

		return true;

	}

	return false;

	return ns_capable_common(ns, cap, true);

}

EXPORT_SYMBOL(ns_capable);



/**

 * ns_capable_noaudit - Determine if the current task has a superior capability

 * (unaudited) in effect

 * @ns:  The usernamespace we want the capability in

 * @cap: The capability to be tested for

 *

 * Return true if the current task has the given superior capability currently

 * available for use, false if not.

 *

 * This sets PF_SUPERPRIV on the task if the capability is available on the

 * assumption that it's about to be used.

 */

bool ns_capable_noaudit(struct user_namespace *ns, int cap)

{

	return ns_capable_common(ns, cap, false);

}

EXPORT_SYMBOL(ns_capable_noaudit);



/**

 * capable - Determine if the current task has a superior capability in effect