From: Wang Weiyang wangweiyang2@huawei.com
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@vger.kernel.org Fixes: 4cef7299b478 ("device_cgroup: add proper checking when changing default behavior") Signed-off-by: Wang Weiyang wangweiyang2@huawei.com Reviewed-by: Aristeu Rozanski aris@redhat.com Signed-off-by: Paul Moore paul@paul-moore.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- security/device_cgroup.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-)
--- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -82,6 +82,17 @@ 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 */ @@ -604,11 +615,13 @@ 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) { @@ -620,15 +633,27 @@ 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))