2019-01-25 07:18:48

by Geliang Tang

Subject: [PATCH] security: keys: add NULL checking for key->type->instantiate

key->type->instantiate can be NULL, add NULL checking to prevent
NULL pointer dereference in __key_instantiate_and_link().

Signed-off-by: Geliang Tang <[email protected]>
---
security/keys/key.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/keys/key.c b/security/keys/key.c
index 44a80d6741a1..ae3cc11be0d2 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -438,7 +438,8 @@ static int __key_instantiate_and_link(struct key *key,
/* can't instantiate twice */
if (key->state == KEY_IS_UNINSTANTIATED) {
/* instantiate the key */
- ret = key->type->instantiate(key, prep);
+ if (key->type->instantiate)
+ ret = key->type->instantiate(key, prep);

if (ret == 0) {
/* mark the key as being instantiated */
--
2.17.1

2019-02-06 22:28:25

by David Howells

Subject: Re: [PATCH] security: keys: add NULL checking for key->type->instantiate

Geliang Tang <[email protected]> wrote:

> key->type->instantiate can be NULL, add NULL checking to prevent
> NULL pointer dereference in __key_instantiate_and_link().

Do you have an oops report or test case for this?

David

2019-02-26 09:09:44

by Geliang Tang

Subject: Re: [PATCH] security: keys: add NULL checking for key->type->instantiate

On Wed, Feb 06, 2019 at 10:26:53PM +0000, David Howells wrote:
> Geliang Tang <[email protected]> wrote:
>
> > key->type->instantiate can be NULL, add NULL checking to prevent
> > NULL pointer dereference in __key_instantiate_and_link().
>
> Do you have an oops report or test case for this?
>
> David

Here is the test module code. Insmod it, we can get the oops.

#include <linux/init.h>
#include <linux/module.h>
#include <linux/key.h>
#include <linux/key-type.h>
#include <linux/cred.h>
#include <linux/seq_file.h>

static int test_instantiate(struct key *key, struct key_preparsed_payload *prep)
{
return 0;
}

static void test_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
}

struct key_type test_key_type = {
.name = "test",
//.instantiate = test_instantiate,
.describe = test_describe,
};

static int __init test_init(void)
{
const struct cred *cred = current_cred();
struct key *key;
int ret;

register_key_type(&test_key_type);

key = key_alloc(&test_key_type, "test",
GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
KEY_POS_SEARCH, KEY_ALLOC_NOT_IN_QUOTA, NULL);
if (IS_ERR(key))
return -1;

pr_info("keyring allocated successfully.\n");

ret = key_instantiate_and_link(key,
NULL,
sizeof(int),
current->cred->user->session_keyring,
NULL);
if (ret < 0) {
key_revoke(key);
key_put(key);
return ret;
}

return 0;
}

static void __exit test_exit(void)
{
unregister_key_type(&test_key_type);
}

module_init(test_init);
module_exit(test_exit);

MODULE_LICENSE("GPL");

2019-02-26 09:13:11

by Geliang Tang

Subject: Re: [PATCH] security: keys: add NULL checking for key->type->instantiate

On Wed, Feb 06, 2019 at 10:26:53PM +0000, David Howells wrote:
> Geliang Tang <[email protected]> wrote:
>
> > key->type->instantiate can be NULL, add NULL checking to prevent
> > NULL pointer dereference in __key_instantiate_and_link().
>
> Do you have an oops report or test case for this?
>
> David

Here is the test module code. Insmod it, we can get the oops.

#include <linux/init.h>
#include <linux/module.h>
#include <linux/key.h>
#include <linux/key-type.h>
#include <linux/cred.h>
#include <linux/seq_file.h>

static int test_instantiate(struct key *key, struct key_preparsed_payload *prep)
{
return 0;
}

static void test_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
}

struct key_type test_key_type = {
.name = "test",
//.instantiate = test_instantiate,
.describe = test_describe,
};

static int __init test_init(void)
{
const struct cred *cred = current_cred();
struct key *key;
int ret;

register_key_type(&test_key_type);

key = key_alloc(&test_key_type, "test",
GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
KEY_POS_SEARCH, KEY_ALLOC_NOT_IN_QUOTA, NULL);
if (IS_ERR(key))
return -1;

pr_info("keyring allocated successfully.\n");

ret = key_instantiate_and_link(key,
NULL,
sizeof(int),
current->cred->user->session_keyring,
NULL);
if (ret < 0) {
key_revoke(key);
key_put(key);
return ret;
}

return 0;
}

static void __exit test_exit(void)
{
unregister_key_type(&test_key_type);
}

module_init(test_init);
module_exit(test_exit);

MODULE_LICENSE("GPL");