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device_cgroup: Roll back to original exceptions after copy failure

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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: 4cef7299b4 ("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>
This commit is contained in:
Wang Weiyang 2022-10-25 19:31:01 +08:00 committed by Paul Moore
parent 86ef3c735e
commit e68bfbd3b3
1 changed files with 30 additions and 5 deletions
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35
security/device_cgroup.c
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@ -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(struct dev_cgroup *devcgroup,
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(struct dev_cgroup *devcgroup,
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;
}
rc = dev_exceptions_copy(&devcgroup->exceptions,
&parent->exceptions);
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) {
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))