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Date: Fri, 17 Jun 2016 10:22:46 -0500
From: "Serge E. Hallyn" <serge@...lyn.com>
To: Topi Miettinen <toiwoton@...il.com>
Cc: linux-kernel@...r.kernel.org,
James Morris <james.l.morris@...cle.com>,
"Serge E. Hallyn" <serge@...lyn.com>,
"open list:SECURITY SUBSYSTEM"
<linux-security-module@...r.kernel.org>
Subject: Re: [RFC 04/18] device_cgroup: track and present accessed devices
Quoting Topi Miettinen (toiwoton@...il.com):
> Track what devices are accessed and present them cgroup devices.accessed.
>
> Signed-off-by: Topi Miettinen <toiwoton@...il.com>
> ---
> security/device_cgroup.c | 70 +++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 60 insertions(+), 10 deletions(-)
>
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index 03c1652..45aa730 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -48,6 +48,7 @@ struct dev_exception_item {
> struct dev_cgroup {
> struct cgroup_subsys_state css;
> struct list_head exceptions;
> + struct list_head accessed;
> enum devcg_behavior behavior;
> };
>
> @@ -90,7 +91,7 @@ free_and_exit:
> /*
> * called under devcgroup_mutex
> */
> -static int dev_exception_add(struct dev_cgroup *dev_cgroup,
> +static int dev_exception_add(struct list_head *exceptions,
> struct dev_exception_item *ex)
If you're going to re-use this function for the accessed list, then it
should be renamed, bc as it is it's misleading.
It also should be restructured. The add-exceptions case was rare, so
doing kmemdup before checking for duplicates was ok. But for the
accessed list I think we want to check for duplicates before we kmemdup.
> {
> struct dev_exception_item *excopy, *walk;
> @@ -101,7 +102,7 @@ static int dev_exception_add(struct dev_cgroup *dev_cgroup,
> if (!excopy)
> return -ENOMEM;
>
> - list_for_each_entry(walk, &dev_cgroup->exceptions, list) {
> + list_for_each_entry(walk, exceptions, list) {
> if (walk->type != ex->type)
> continue;
> if (walk->major != ex->major)
> @@ -115,7 +116,7 @@ static int dev_exception_add(struct dev_cgroup *dev_cgroup,
> }
>
> if (excopy != NULL)
> - list_add_tail_rcu(&excopy->list, &dev_cgroup->exceptions);
> + list_add_tail_rcu(&excopy->list, exceptions);
> return 0;
> }
>
> @@ -155,6 +156,16 @@ static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
> }
> }
>
> +static void dev_accessed_clean(struct dev_cgroup *dev_cgroup)
> +{
> + struct dev_exception_item *ex, *tmp;
> +
> + list_for_each_entry_safe(ex, tmp, &dev_cgroup->accessed, list) {
> + list_del_rcu(&ex->list);
> + kfree_rcu(ex, rcu);
> + }
> +}
> +
> /**
> * dev_exception_clean - frees all entries of the exception list
> * @dev_cgroup: dev_cgroup with the exception list to be cleaned
> @@ -221,6 +232,7 @@ devcgroup_css_alloc(struct cgroup_subsys_state *parent_css)
> if (!dev_cgroup)
> return ERR_PTR(-ENOMEM);
> INIT_LIST_HEAD(&dev_cgroup->exceptions);
> + INIT_LIST_HEAD(&dev_cgroup->accessed);
> dev_cgroup->behavior = DEVCG_DEFAULT_NONE;
>
> return &dev_cgroup->css;
> @@ -231,6 +243,7 @@ static void devcgroup_css_free(struct cgroup_subsys_state *css)
> struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
>
> __dev_exception_clean(dev_cgroup);
> + dev_accessed_clean(dev_cgroup);
> kfree(dev_cgroup);
> }
>
> @@ -272,9 +285,9 @@ static void set_majmin(char *str, unsigned m)
> sprintf(str, "%u", m);
> }
>
> -static int devcgroup_seq_show(struct seq_file *m, void *v)
> +static int devcgroup_seq_show_list(struct seq_file *m, struct dev_cgroup *devcgroup,
> + struct list_head *exceptions, bool allow)
> {
> - struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
> struct dev_exception_item *ex;
> char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
>
> @@ -285,14 +298,14 @@ static int devcgroup_seq_show(struct seq_file *m, void *v)
> * - List the exceptions in case the default policy is to deny
> * This way, the file remains as a "whitelist of devices"
> */
> - if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
> + if (allow) {
> set_access(acc, ACC_MASK);
> set_majmin(maj, ~0);
> set_majmin(min, ~0);
> seq_printf(m, "%c %s:%s %s\n", type_to_char(DEV_ALL),
> maj, min, acc);
> } else {
> - list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
> + list_for_each_entry_rcu(ex, exceptions, list) {
> set_access(acc, ex->access);
> set_majmin(maj, ex->major);
> set_majmin(min, ex->minor);
> @@ -305,6 +318,36 @@ static int devcgroup_seq_show(struct seq_file *m, void *v)
> return 0;
> }
>
> +static int devcgroup_seq_show(struct seq_file *m, void *v)
> +{
> + struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
> +
> + return devcgroup_seq_show_list(m, devcgroup, &devcgroup->exceptions,
> + devcgroup->behavior == DEVCG_DEFAULT_ALLOW);
> +}
> +
> +static int devcgroup_seq_show_accessed(struct seq_file *m, void *v)
> +{
> + struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
> +
> + return devcgroup_seq_show_list(m, devcgroup, &devcgroup->accessed, false);
> +}
> +
> +static void devcgroup_add_accessed(struct dev_cgroup *dev_cgroup, short type,
> + u32 major, u32 minor, short access)
> +{
> + struct dev_exception_item ex;
> +
> + ex.type = type;
> + ex.major = major;
> + ex.minor = minor;
> + ex.access = access;
> +
> + mutex_lock(&devcgroup_mutex);
> + dev_exception_add(&dev_cgroup->accessed, &ex);
> + mutex_unlock(&devcgroup_mutex);
> +}
> +
> /**
> * match_exception - iterates the exception list trying to find a complete match
> * @exceptions: list of exceptions
> @@ -566,7 +609,7 @@ static int propagate_exception(struct dev_cgroup *devcg_root,
> */
> if (devcg_root->behavior == DEVCG_DEFAULT_ALLOW &&
> devcg->behavior == DEVCG_DEFAULT_ALLOW) {
> - rc = dev_exception_add(devcg, ex);
> + rc = dev_exception_add(&devcg->exceptions, ex);
> if (rc)
> break;
> } else {
> @@ -736,7 +779,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
>
> if (!parent_has_perm(devcgroup, &ex))
> return -EPERM;
> - rc = dev_exception_add(devcgroup, &ex);
> + rc = dev_exception_add(&devcgroup->exceptions, &ex);
> break;
> case DEVCG_DENY:
> /*
> @@ -747,7 +790,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
> if (devcgroup->behavior == DEVCG_DEFAULT_DENY)
> dev_exception_rm(devcgroup, &ex);
> else
> - rc = dev_exception_add(devcgroup, &ex);
> + rc = dev_exception_add(&devcgroup->exceptions, &ex);
>
> if (rc)
> break;
> @@ -788,6 +831,11 @@ static struct cftype dev_cgroup_files[] = {
> .seq_show = devcgroup_seq_show,
> .private = DEVCG_LIST,
> },
> + {
> + .name = "accessed",
> + .seq_show = devcgroup_seq_show_accessed,
> + .private = DEVCG_LIST,
> + },
> { } /* terminate */
> };
>
> @@ -830,6 +878,8 @@ static int __devcgroup_check_permission(short type, u32 major, u32 minor,
> if (!rc)
> return -EPERM;
>
> + devcgroup_add_accessed(dev_cgroup, type, major, minor, access);
> +
> return 0;
> }
>
> --
> 2.8.1
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