From: Wang Weiyang <wangweiyang2@xxxxxxxxxx>
commit e68bfbd3b3c3a0ec3cf8c230996ad8cabe90322f upstream.
When add the 'a *:* rwm' entry to devcgroup A's whitelist, at first A's
exceptions will be cleaned and A's behavior is changed to
DEVCG_DEFAULT_ALLOW. Then parent's exceptions will be copyed to A's
whitelist. If copy failure occurs, just return leaving A to grant
permissions to all devices. And A may grant more permissions than
parent.
Backup A's whitelist and recover original exceptions after copy
failure.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 4cef7299b478 ("device_cgroup: add proper checking when changing default behavior")
Signed-off-by: Wang Weiyang <wangweiyang2@xxxxxxxxxx>
Reviewed-by: Aristeu Rozanski <aris@xxxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
security/device_cgroup.c | 33 +++++++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -87,6 +87,17 @@ free_and_exit:
return -ENOMEM;
}
+static void dev_exceptions_move(struct list_head *dest, struct list_head *orig)
+{
+ struct dev_exception_item *ex, *tmp;
+
+ lockdep_assert_held(&devcgroup_mutex);
+
+ list_for_each_entry_safe(ex, tmp, orig, list) {
+ list_move_tail(&ex->list, dest);
+ }
+}
+
/*
* called under devcgroup_mutex
*/
@@ -608,11 +619,13 @@ static int devcgroup_update_access(struc
int count, rc = 0;
struct dev_exception_item ex;
struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
+ struct dev_cgroup tmp_devcgrp;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
memset(&ex, 0, sizeof(ex));
+ memset(&tmp_devcgrp, 0, sizeof(tmp_devcgrp));
b = buffer;
switch (*b) {
@@ -624,15 +637,27 @@ static int devcgroup_update_access(struc
if (!may_allow_all(parent))
return -EPERM;
- dev_exception_clean(devcgroup);
- devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
- if (!parent)
+ if (!parent) {
+ devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
+ dev_exception_clean(devcgroup);
break;
+ }
+ INIT_LIST_HEAD(&tmp_devcgrp.exceptions);
+ rc = dev_exceptions_copy(&tmp_devcgrp.exceptions,
+ &devcgroup->exceptions);
+ if (rc)
+ return rc;
+ dev_exception_clean(devcgroup);
rc = dev_exceptions_copy(&devcgroup->exceptions,
&parent->exceptions);
- if (rc)
+ if (rc) {
+ dev_exceptions_move(&devcgroup->exceptions,
+ &tmp_devcgrp.exceptions);
return rc;
+ }
+ devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
+ dev_exception_clean(&tmp_devcgrp);
break;
case DEVCG_DENY:
if (css_has_online_children(&devcgroup->css))
