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Message-ID: <CACE9dm-gJ72B5fp2KrY6rV=-Ydnu66mU1xQmng7ZvT1WiTa67Q@mail.gmail.com>
Date: Wed, 9 Nov 2016 01:40:02 +0200
From: Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To: Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc: linux-security-module <linux-security-module@...r.kernel.org>,
linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
linux-ima-devel <linux-ima-devel@...ts.sourceforge.net>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Linux-ima-devel] [PATCH v6 07/10] ima: store the builtin/custom
template definitions in a list
On Fri, Oct 21, 2016 at 5:44 AM, Thiago Jung Bauermann
<bauerman@...ux.vnet.ibm.com> wrote:
> From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
>
> The builtin and single custom templates are currently stored in an
> array. In preparation for being able to restore a measurement list
> containing multiple builtin/custom templates, this patch stores the
> builtin and custom templates as a linked list. This will permit
> defining more than one custom template per boot.
>
> Changelog v4:
> - fix "spinlock bad magic" BUG - reported by Dmitry Vyukov
>
> Changelog v3:
> - initialize template format list in ima_template_desc_current(), as it
> might be called during __setup before normal initialization. (kernel
> test robot)
> - remove __init annotation of ima_init_template_list()
>
> Changelog v2:
> - fix lookup_template_desc() preemption imbalance (kernel test robot)
>
> Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
> ---
> security/integrity/ima/ima.h | 2 ++
> security/integrity/ima/ima_main.c | 1 +
> security/integrity/ima/ima_template.c | 52 +++++++++++++++++++++++++++--------
> 3 files changed, 44 insertions(+), 11 deletions(-)
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 139dec67dcbf..6b0540ad189f 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -85,6 +85,7 @@ struct ima_template_field {
>
> /* IMA template descriptor definition */
> struct ima_template_desc {
> + struct list_head list;
> char *name;
> char *fmt;
> int num_fields;
> @@ -146,6 +147,7 @@ int ima_restore_measurement_list(loff_t bufsize, void *buf);
> int ima_measurements_show(struct seq_file *m, void *v);
> unsigned long ima_get_binary_runtime_size(void);
> int ima_init_template(void);
> +void ima_init_template_list(void);
>
> /*
> * used to protect h_table and sha_table
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 423d111b3b94..50818c60538b 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -418,6 +418,7 @@ static int __init init_ima(void)
> {
> int error;
>
> + ima_init_template_list();
> hash_setup(CONFIG_IMA_DEFAULT_HASH);
> error = ima_init();
> if (!error) {
> diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
> index 37f972cb05fe..c0d808c20c40 100644
> --- a/security/integrity/ima/ima_template.c
> +++ b/security/integrity/ima/ima_template.c
> @@ -15,16 +15,20 @@
>
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> +#include <linux/rculist.h>
> #include "ima.h"
> #include "ima_template_lib.h"
>
> -static struct ima_template_desc defined_templates[] = {
> +static struct ima_template_desc builtin_templates[] = {
> {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
> {.name = "ima-ng", .fmt = "d-ng|n-ng"},
> {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
> {.name = "", .fmt = ""}, /* placeholder for a custom format */
> };
>
> +static LIST_HEAD(defined_templates);
> +static DEFINE_SPINLOCK(template_list);
> +
> static struct ima_template_field supported_fields[] = {
> {.field_id = "d", .field_init = ima_eventdigest_init,
> .field_show = ima_show_template_digest},
> @@ -53,6 +57,8 @@ static int __init ima_template_setup(char *str)
> if (ima_template)
> return 1;
>
> + ima_init_template_list();
> +
> /*
> * Verify that a template with the supplied name exists.
> * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
> @@ -81,7 +87,7 @@ __setup("ima_template=", ima_template_setup);
>
> static int __init ima_template_fmt_setup(char *str)
> {
> - int num_templates = ARRAY_SIZE(defined_templates);
> + int num_templates = ARRAY_SIZE(builtin_templates);
>
> if (ima_template)
> return 1;
> @@ -92,22 +98,28 @@ static int __init ima_template_fmt_setup(char *str)
> return 1;
> }
>
> - defined_templates[num_templates - 1].fmt = str;
> - ima_template = defined_templates + num_templates - 1;
> + builtin_templates[num_templates - 1].fmt = str;
> + ima_template = builtin_templates + num_templates - 1;
> +
> return 1;
> }
> __setup("ima_template_fmt=", ima_template_fmt_setup);
>
> static struct ima_template_desc *lookup_template_desc(const char *name)
> {
> - int i;
> + struct ima_template_desc *template_desc;
> + int found = 0;
>
> - for (i = 0; i < ARRAY_SIZE(defined_templates); i++) {
> - if (strcmp(defined_templates[i].name, name) == 0)
> - return defined_templates + i;
> + rcu_read_lock();
> + list_for_each_entry_rcu(template_desc, &defined_templates, list) {
> + if ((strcmp(template_desc->name, name) == 0) ||
> + (strcmp(template_desc->fmt, name) == 0)) {
> + found = 1;
> + break;
> + }
> }
> -
> - return NULL;
> + rcu_read_unlock();
> + return found ? template_desc : NULL;
> }
>
> static struct ima_template_field *lookup_template_field(const char *field_id)
> @@ -183,11 +195,29 @@ static int template_desc_init_fields(const char *template_fmt,
> return 0;
> }
>
> +void ima_init_template_list(void)
> +{
> + int i;
> +
> + if (!list_empty(&defined_templates))
> + return;
> +
> + spin_lock(&template_list);
> + for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
> + list_add_tail_rcu(&builtin_templates[i].list,
> + &defined_templates);
> + }
> + spin_unlock(&template_list);
> + synchronize_rcu();
Btw, what is the purpose of synchronize rcu here?
i think it make sense before deleting the object, like:
--------------------------------
list_del_rcu(&p->list);
spin_unlock(&listmutex);
synchronize_rcu();
kfree(p);
--------------------------------
I think it is never deleted.
There is another similar place in the same file...
> +}
> +
> struct ima_template_desc *ima_template_desc_current(void)
> {
> - if (!ima_template)
> + if (!ima_template) {
> + ima_init_template_list();
> ima_template =
> lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
> + }
> return ima_template;
> }
>
> --
> 2.7.4
>
>
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--
Thanks,
Dmitry
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