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Commit 26a41cd1 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-3.15-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 

Pull cgroup fixes from Tejun Heo:
 "During recent restructuring, device_cgroup unified config input check
  and enforcement logic; unfortunately, it turned out to share too much.
  Aristeu's patches fix the breakage and marked for -stable backport.

  The other two patches are fallouts from kernfs conversion.  The blkcg
  change is temporary and will go away once kernfs internal locking gets
  simplified (patches pending)"

* 'for-3.15-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  blkcg: use trylock on blkcg_pol_mutex in blkcg_reset_stats()
  device_cgroup: check if exception removal is allowed
  device_cgroup: fix the comment format for recently added functions
  device_cgroup: rework device access check and exception checking
  cgroup: fix the retry path of cgroup_mount()
parents 619b5891 36c38fb7

block/blk-cgroup.c

+14 −1
Original line number Diff line number Diff line
@@ -451,7 +451,20 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css, 
	struct blkcg_gq *blkg;

	int i;



	mutex_lock(&blkcg_pol_mutex);

	/*

	 * XXX: We invoke cgroup_add/rm_cftypes() under blkcg_pol_mutex

	 * which ends up putting cgroup's internal cgroup_tree_mutex under

	 * it; however, cgroup_tree_mutex is nested above cgroup file

	 * active protection and grabbing blkcg_pol_mutex from a cgroup

	 * file operation creates a possible circular dependency.  cgroup

	 * internal locking is planned to go through further simplification

	 * and this issue should go away soon.  For now, let's trylock

	 * blkcg_pol_mutex and restart the write on failure.

	 *

	 * http://lkml.kernel.org/g/5363C04B.4010400@oracle.com

	 */

	if (!mutex_trylock(&blkcg_pol_mutex))

		return restart_syscall();

	spin_lock_irq(&blkcg->lock);



	/*

kernel/cgroup.c

+4 −4
Original line number Diff line number Diff line
@@ -1495,7 +1495,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	 */

	if (!use_task_css_set_links)

		cgroup_enable_task_cg_lists();

retry:



	mutex_lock(&cgroup_tree_mutex);

	mutex_lock(&cgroup_mutex);
@@ -1503,7 +1503,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	ret = parse_cgroupfs_options(data, &opts);

	if (ret)

		goto out_unlock;



retry:

	/* look for a matching existing root */

	if (!opts.subsys_mask && !opts.none && !opts.name) {

		cgrp_dfl_root_visible = true;
@@ -1562,9 +1562,9 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		if (!atomic_inc_not_zero(&root->cgrp.refcnt)) {

			mutex_unlock(&cgroup_mutex);

			mutex_unlock(&cgroup_tree_mutex);

			kfree(opts.release_agent);

			kfree(opts.name);

			msleep(10);

			mutex_lock(&cgroup_tree_mutex);

			mutex_lock(&cgroup_mutex);

			goto retry;

		}

security/device_cgroup.c

+159 −43
Original line number Diff line number Diff line
@@ -306,57 +306,138 @@ static int devcgroup_seq_show(struct seq_file *m, void *v) 
}



/**

 * may_access - verifies if a new exception is part of what is allowed

 *		by a dev cgroup based on the default policy +

 *		exceptions. This is used to make sure a child cgroup

 *		won't have more privileges than its parent or to

 *		verify if a certain access is allowed.

 * @dev_cgroup: dev cgroup to be tested against

 * @refex: new exception

 * @behavior: behavior of the exception

 * match_exception	- iterates the exception list trying to find a complete match

 * @exceptions: list of exceptions

 * @type: device type (DEV_BLOCK or DEV_CHAR)

 * @major: device file major number, ~0 to match all

 * @minor: device file minor number, ~0 to match all

 * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD)

 *

 * It is considered a complete match if an exception is found that will

 * contain the entire range of provided parameters.

 *

 * Return: true in case it matches an exception completely

 */

static bool may_access(struct dev_cgroup *dev_cgroup,

		       struct dev_exception_item *refex,

		       enum devcg_behavior behavior)

static bool match_exception(struct list_head *exceptions, short type,

			    u32 major, u32 minor, short access)

{

	struct dev_exception_item *ex;

	bool match = false;



	rcu_lockdep_assert(rcu_read_lock_held() ||

			   lockdep_is_held(&devcgroup_mutex),

			   "device_cgroup::may_access() called without proper synchronization");

	list_for_each_entry_rcu(ex, exceptions, list) {

		if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))

			continue;

		if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR))

			continue;

		if (ex->major != ~0 && ex->major != major)

			continue;

		if (ex->minor != ~0 && ex->minor != minor)

			continue;

		/* provided access cannot have more than the exception rule */

		if (access & (~ex->access))

			continue;

		return true;

	}

	return false;

}



/**

 * match_exception_partial - iterates the exception list trying to find a partial match

 * @exceptions: list of exceptions

 * @type: device type (DEV_BLOCK or DEV_CHAR)

 * @major: device file major number, ~0 to match all

 * @minor: device file minor number, ~0 to match all

 * @access: permission mask (ACC_READ, ACC_WRITE, ACC_MKNOD)

 *

 * It is considered a partial match if an exception's range is found to

 * contain *any* of the devices specified by provided parameters. This is

 * used to make sure no extra access is being granted that is forbidden by

 * any of the exception list.

 *

 * Return: true in case the provided range mat matches an exception completely

 */

static bool match_exception_partial(struct list_head *exceptions, short type,

				    u32 major, u32 minor, short access)

{

	struct dev_exception_item *ex;



	list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {

		if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))

	list_for_each_entry_rcu(ex, exceptions, list) {

		if ((type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))

			continue;

		if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))

		if ((type & DEV_CHAR) && !(ex->type & DEV_CHAR))

			continue;

		if (ex->major != ~0 && ex->major != refex->major)

		/*

		 * We must be sure that both the exception and the provided

		 * range aren't masking all devices

		 */

		if (ex->major != ~0 && major != ~0 && ex->major != major)

			continue;

		if (ex->minor != ~0 && ex->minor != refex->minor)

		if (ex->minor != ~0 && minor != ~0 && ex->minor != minor)

			continue;

		if (refex->access & (~ex->access))

		/*

		 * In order to make sure the provided range isn't matching

		 * an exception, all its access bits shouldn't match the

		 * exception's access bits

		 */

		if (!(access & ex->access))

			continue;

		match = true;

		break;

		return true;

	}

	return false;

}



/**

 * verify_new_ex - verifies if a new exception is allowed by parent cgroup's permissions

 * @dev_cgroup: dev cgroup to be tested against

 * @refex: new exception

 * @behavior: behavior of the exception's dev_cgroup

 *

 * This is used to make sure a child cgroup won't have more privileges

 * than its parent

 */

static bool verify_new_ex(struct dev_cgroup *dev_cgroup,

		          struct dev_exception_item *refex,

		          enum devcg_behavior behavior)

{

	bool match = false;



	rcu_lockdep_assert(rcu_read_lock_held() ||

			   lockdep_is_held(&devcgroup_mutex),

			   "device_cgroup:verify_new_ex called without proper synchronization");



	if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {

		if (behavior == DEVCG_DEFAULT_ALLOW) {

			/* the exception will deny access to certain devices */

			/*

			 * new exception in the child doesn't matter, only

			 * adding extra restrictions

			 */ 

			return true;

		} else {

			/* the exception will allow access to certain devices */

			if (match)

			/*

				 * a new exception allowing access shouldn't

				 * match an parent's exception

			 * new exception in the child will add more devices

			 * that can be acessed, so it can't match any of

			 * parent's exceptions, even slightly

			 */ 

			match = match_exception_partial(&dev_cgroup->exceptions,

							refex->type,

							refex->major,

							refex->minor,

							refex->access);



			if (match)

				return false;

			return true;

		}

	} else {

		/* only behavior == DEVCG_DEFAULT_DENY allowed here */

		/*

		 * Only behavior == DEVCG_DEFAULT_DENY allowed here, therefore

		 * the new exception will add access to more devices and must

		 * be contained completely in an parent's exception to be

		 * allowed

		 */

		match = match_exception(&dev_cgroup->exceptions, refex->type,

					refex->major, refex->minor,

					refex->access);



		if (match)

			/* parent has an exception that matches the proposed */

			return true;
@@ -378,7 +459,38 @@ static int parent_has_perm(struct dev_cgroup *childcg, 


	if (!parent)

		return 1;

	return may_access(parent, ex, childcg->behavior);

	return verify_new_ex(parent, ex, childcg->behavior);

}



/**

 * parent_allows_removal - verify if it's ok to remove an exception

 * @childcg: child cgroup from where the exception will be removed

 * @ex: exception being removed

 *

 * When removing an exception in cgroups with default ALLOW policy, it must

 * be checked if removing it will give the child cgroup more access than the

 * parent.

 *

 * Return: true if it's ok to remove exception, false otherwise

 */

static bool parent_allows_removal(struct dev_cgroup *childcg,

				  struct dev_exception_item *ex)

{

	struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));



	if (!parent)

		return true;



	/* It's always allowed to remove access to devices */

	if (childcg->behavior == DEVCG_DEFAULT_DENY)

		return true;



	/*

	 * Make sure you're not removing part or a whole exception existing in

	 * the parent cgroup

	 */

	return !match_exception_partial(&parent->exceptions, ex->type,

					ex->major, ex->minor, ex->access);

}



/**
@@ -616,17 +728,21 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, 


	switch (filetype) {

	case DEVCG_ALLOW:

		if (!parent_has_perm(devcgroup, &ex))

			return -EPERM;

		/*

		 * If the default policy is to allow by default, try to remove

		 * an matching exception instead. And be silent about it: we

		 * don't want to break compatibility

		 */

		if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {

			/* Check if the parent allows removing it first */

			if (!parent_allows_removal(devcgroup, &ex))

				return -EPERM;

			dev_exception_rm(devcgroup, &ex);

			return 0;

			break;

		}



		if (!parent_has_perm(devcgroup, &ex))

			return -EPERM;

		rc = dev_exception_add(devcgroup, &ex);

		break;

	case DEVCG_DENY:
@@ -704,18 +820,18 @@ static int __devcgroup_check_permission(short type, u32 major, u32 minor, 
				        short access)

{

	struct dev_cgroup *dev_cgroup;

	struct dev_exception_item ex;

	int rc;



	memset(&ex, 0, sizeof(ex));

	ex.type = type;

	ex.major = major;

	ex.minor = minor;

	ex.access = access;

	bool rc;



	rcu_read_lock();

	dev_cgroup = task_devcgroup(current);

	rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior);

	if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW)

		/* Can't match any of the exceptions, even partially */

		rc = !match_exception_partial(&dev_cgroup->exceptions,

					      type, major, minor, access);

	else

		/* Need to match completely one exception to be allowed */

		rc = match_exception(&dev_cgroup->exceptions, type, major,

				     minor, access);

	rcu_read_unlock();



	if (!rc)