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author | Aristeu Rozanski <aris@redhat.com> | 2013-02-15 11:55:45 -0500 |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2013-03-20 07:50:13 -0700 |
commit | c39a2a3018f8065cb5ea38b0314c1bbedb2cfa0d (patch) | |
tree | a930f23ff557c701e91e826940d37ad0c9b38fd0 /security | |
parent | 26898fdff371d78f122cf15d8732d1d37f2d1338 (diff) | |
download | lwn-c39a2a3018f8065cb5ea38b0314c1bbedb2cfa0d.tar.gz lwn-c39a2a3018f8065cb5ea38b0314c1bbedb2cfa0d.zip |
devcg: prepare may_access() for hierarchy support
Currently may_access() is only able to verify if an exception is valid for the
current cgroup, which has the same behavior. With hierarchy, it'll be also used
to verify if a cgroup local exception is valid towards its cgroup parent, which
might have different behavior.
v2:
- updated patch description
- rebased on top of a new patch to expand the may_access() logic to make it
more clear
- fixed argument description order in may_access()
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'security')
-rw-r--r-- | security/device_cgroup.c | 49 |
1 files changed, 31 insertions, 18 deletions
diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 4ad55a9c6920..ddf3c709c0c2 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -25,6 +25,12 @@ static DEFINE_MUTEX(devcgroup_mutex); +enum devcg_behavior { + DEVCG_DEFAULT_NONE, + DEVCG_DEFAULT_ALLOW, + DEVCG_DEFAULT_DENY, +}; + /* * exception list locking rules: * hold devcgroup_mutex for update/read. @@ -42,10 +48,7 @@ struct dev_exception_item { struct dev_cgroup { struct cgroup_subsys_state css; struct list_head exceptions; - enum { - DEVCG_DEFAULT_ALLOW, - DEVCG_DEFAULT_DENY, - } behavior; + enum devcg_behavior behavior; }; static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s) @@ -304,9 +307,11 @@ static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft, * verify if a certain access is allowed. * @dev_cgroup: dev cgroup to be tested against * @refex: new exception + * @behavior: behavior of the exception */ static bool may_access(struct dev_cgroup *dev_cgroup, - struct dev_exception_item *refex) + struct dev_exception_item *refex, + enum devcg_behavior behavior) { struct dev_exception_item *ex; bool match = false; @@ -330,19 +335,27 @@ static bool may_access(struct dev_cgroup *dev_cgroup, break; } - /* - * In two cases we'll consider this new exception valid: - * - the dev cgroup has its default policy to deny + exception list: - * the new exception *should* match the exceptions - * - the dev cgroup has its default policy to allow + exception list: - * the new exception should *not* match any of the exceptions - */ - if (dev_cgroup->behavior == DEVCG_DEFAULT_DENY) { - if (match) + if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { + if (behavior == DEVCG_DEFAULT_ALLOW) { + /* the exception will deny access to certain devices */ + 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 + */ + return false; return true; + } } else { - if (!match) + /* only behavior == DEVCG_DEFAULT_DENY allowed here */ + if (match) + /* parent has an exception that matches the proposed */ return true; + else + return false; } return false; } @@ -361,7 +374,7 @@ static int parent_has_perm(struct dev_cgroup *childcg, if (!pcg) return 1; parent = cgroup_to_devcgroup(pcg); - return may_access(parent, ex); + return may_access(parent, ex, childcg->behavior); } /** @@ -395,7 +408,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, { const char *b; char temp[12]; /* 11 + 1 characters needed for a u32 */ - int count, rc; + int count, rc = 0; struct dev_exception_item ex; struct cgroup *p = devcgroup->css.cgroup; struct dev_cgroup *parent = NULL; @@ -612,7 +625,7 @@ static int __devcgroup_check_permission(short type, u32 major, u32 minor, rcu_read_lock(); dev_cgroup = task_devcgroup(current); - rc = may_access(dev_cgroup, &ex); + rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior); rcu_read_unlock(); if (!rc) |