lkml.org 
[lkml]   [2022]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] device_cgroup: Roll back to original exceptions after copy failure
On Tue, Oct 25, 2022 at 07:31:01PM +0800, Wang Weiyang wrote:
> 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.
>
> Fixes: 4cef7299b478 ("device_cgroup: add proper checking when changing default behavior")
> Signed-off-by: Wang Weiyang <wangweiyang2@huawei.com>
> ---
> security/device_cgroup.c | 33 +++++++++++++++++++++++++++++----
> 1 file changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index a9f8c63a96d1..bef2b9285fb3 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -82,6 +82,17 @@ static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
> 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;
> + }
>
> + 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))

Reviewed-by: Aristeu Rozanski <aris@redhat.com>

--
Aristeu

\
 
 \ /
  Last update: 2022-11-07 19:58    [W:0.235 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site