* [PATCH] landlock: Initialize kernel stack variables properly
@ 2021-11-03 7:14 Austin Kim
2021-11-03 12:17 ` Mickaël Salaün
0 siblings, 1 reply; 4+ messages in thread
From: Austin Kim @ 2021-11-03 7:14 UTC (permalink / raw)
To: mic, serge; +Cc: serge, linux-security-module, linux-kernel, austindh.kim
In case kernel stack variables are not initialized properly, there might
be a little chance of kernel information disclosure. So it is better for
kernel stack variables to be initialized with null characters.
Signed-off-by: Austin Kim <austindh.kim@gmail.com>
---
security/landlock/syscalls.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 32396962f04d..50a6f7091428 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule,
if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
return -EINVAL;
+ memset(&path_beneath_attr, 0, sizeof(path_beneath_attr));
+
/* Copies raw user space buffer, only one type for now. */
res = copy_from_user(&path_beneath_attr, rule_attr,
sizeof(path_beneath_attr));
--
2.20.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] landlock: Initialize kernel stack variables properly
2021-11-03 7:14 [PATCH] landlock: Initialize kernel stack variables properly Austin Kim
@ 2021-11-03 12:17 ` Mickaël Salaün
2021-11-04 11:41 ` Austin Kim
0 siblings, 1 reply; 4+ messages in thread
From: Mickaël Salaün @ 2021-11-03 12:17 UTC (permalink / raw)
To: Austin Kim, serge; +Cc: linux-security-module, linux-kernel
Hi Austin,
On 03/11/2021 08:14, Austin Kim wrote:
> In case kernel stack variables are not initialized properly, there might
> be a little chance of kernel information disclosure. So it is better for
> kernel stack variables to be initialized with null characters.
>
> Signed-off-by: Austin Kim <austindh.kim@gmail.com>
> ---
> security/landlock/syscalls.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index 32396962f04d..50a6f7091428 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c
> @@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule,
> if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
> return -EINVAL;
>
> + memset(&path_beneath_attr, 0, sizeof(path_beneath_attr));
> +
This memset is already done with the copy_from_user() call just below.
> /* Copies raw user space buffer, only one type for now. */
> res = copy_from_user(&path_beneath_attr, rule_attr,
> sizeof(path_beneath_attr));
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] landlock: Initialize kernel stack variables properly
2021-11-03 12:17 ` Mickaël Salaün
@ 2021-11-04 11:41 ` Austin Kim
2021-11-05 16:58 ` J Freyensee
0 siblings, 1 reply; 4+ messages in thread
From: Austin Kim @ 2021-11-04 11:41 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Serge E. Hallyn, linux-security-module, Linux Kernel Mailing List
2021년 11월 3일 (수) 오후 9:14, Mickaël Salaün <mic@digikod.net>님이 작성:
>
> Hi Austin,
>
> On 03/11/2021 08:14, Austin Kim wrote:
> > In case kernel stack variables are not initialized properly, there might
> > be a little chance of kernel information disclosure. So it is better for
> > kernel stack variables to be initialized with null characters.
> >
> > Signed-off-by: Austin Kim <austindh.kim@gmail.com>
> > ---
> > security/landlock/syscalls.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> > index 32396962f04d..50a6f7091428 100644
> > --- a/security/landlock/syscalls.c
> > +++ b/security/landlock/syscalls.c
> > @@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule,
> > if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
> > return -EINVAL;
> >
> > + memset(&path_beneath_attr, 0, sizeof(path_beneath_attr));
> > +
>
> This memset is already done with the copy_from_user() call just below.
>
It seems that memset() is done inside copy_from_user().
Thanks for feedback.
BR,
Austin Kim
> > /* Copies raw user space buffer, only one type for now. */
> > res = copy_from_user(&path_beneath_attr, rule_attr,
> > sizeof(path_beneath_attr));
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] landlock: Initialize kernel stack variables properly
2021-11-04 11:41 ` Austin Kim
@ 2021-11-05 16:58 ` J Freyensee
0 siblings, 0 replies; 4+ messages in thread
From: J Freyensee @ 2021-11-05 16:58 UTC (permalink / raw)
To: Austin Kim, Mickaël Salaün
Cc: Serge E. Hallyn, linux-security-module, Linux Kernel Mailing List
On 11/4/21 4:41 AM, Austin Kim wrote:
> 2021년 11월 3일 (수) 오후 9:14, Mickaël Salaün <mic@digikod.net>님이 작성:
>> Hi Austin,
>>
>> On 03/11/2021 08:14, Austin Kim wrote:
>>> In case kernel stack variables are not initialized properly, there might
>>> be a little chance of kernel information disclosure. So it is better for
>>> kernel stack variables to be initialized with null characters.
>>>
>>> Signed-off-by: Austin Kim <austindh.kim@gmail.com>
>>> ---
>>> security/landlock/syscalls.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
>>> index 32396962f04d..50a6f7091428 100644
>>> --- a/security/landlock/syscalls.c
>>> +++ b/security/landlock/syscalls.c
>>> @@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule,
>>> if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
>>> return -EINVAL;
>>>
>>> + memset(&path_beneath_attr, 0, sizeof(path_beneath_attr));
>>> +
>> This memset is already done with the copy_from_user() call just below.
>>
> It seems that memset() is done inside copy_from_user().
> Thanks for feedback.
If you are really sensitive of what information may be disclosed in this
case you can consider memzero_explicit() to use instead:
https://www.kernel.org/doc/htmldocs/kernel-api/API-memzero-explicit.html
Jay
>
> BR,
> Austin Kim
>
>>> /* Copies raw user space buffer, only one type for now. */
>>> res = copy_from_user(&path_beneath_attr, rule_attr,
>>> sizeof(path_beneath_attr));
>>>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-11-03 7:14 [PATCH] landlock: Initialize kernel stack variables properly Austin Kim
2021-11-03 12:17 ` Mickaël Salaün
2021-11-04 11:41 ` Austin Kim
2021-11-05 16:58 ` J Freyensee
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