2022-01-21 21:13:19

by Jiasheng Jiang

Subject: [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

As the possible failure of the kmalloc(), the not_checked and checked
could be NULL pointer.
Therefore, it should be better to check it in order to avoid the
dereference of the NULL pointer.
Also, we need to kfree the 'not_checked' and 'checked' to avoid
the memory leak if fails.
And since it is just a test, it may directly return without error
number.

Fixes: ae2e1aad3e48 ("drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds checks")
Signed-off-by: Jiasheng Jiang <[email protected]>
---
Changelog

v1 -> v2

* Change 1. Add the kfree if fails.

v2 -> v3

* Change 1. Add pr_err if fails.

v3 -> v4

* Change 1. Revert to v2 that remove the pr_err.
---
drivers/misc/lkdtm/bugs.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 4282b625200f..072e3b742edf 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -248,6 +248,11 @@ void lkdtm_ARRAY_BOUNDS(void)

not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
+ if (!not_checked || !checked) {
+ kfree(not_checked);
+ kfree(checked);
+ return;
+ }

pr_info("Array access within bounds ...\n");
/* For both, touch all bytes in the actual member size. */
--
2.25.1

2022-01-21 22:29:54

by Kees Cook

Subject: Re: [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

On Thu, Jan 20, 2022 at 05:29:36PM +0800, Jiasheng Jiang wrote:
> As the possible failure of the kmalloc(), the not_checked and checked
> could be NULL pointer.
> Therefore, it should be better to check it in order to avoid the
> dereference of the NULL pointer.
> Also, we need to kfree the 'not_checked' and 'checked' to avoid
> the memory leak if fails.
> And since it is just a test, it may directly return without error
> number.
>
> Fixes: ae2e1aad3e48 ("drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds checks")
> Signed-off-by: Jiasheng Jiang <[email protected]>
> ---
> Changelog
>
> v1 -> v2
>
> * Change 1. Add the kfree if fails.
>
> v2 -> v3
>
> * Change 1. Add pr_err if fails.
>
> v3 -> v4
>
> * Change 1. Revert to v2 that remove the pr_err.
> ---
> drivers/misc/lkdtm/bugs.c | 5 +++++
> 1 file changed, 5 insertions(+)

Acked-by: Kees Cook <[email protected]>

>
> diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
> index 4282b625200f..072e3b742edf 100644
> --- a/drivers/misc/lkdtm/bugs.c
> +++ b/drivers/misc/lkdtm/bugs.c
> @@ -248,6 +248,11 @@ void lkdtm_ARRAY_BOUNDS(void)
>
> not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
> checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
> + if (!not_checked || !checked) {
> + kfree(not_checked);
> + kfree(checked);
> + return;
> + }
>
> pr_info("Array access within bounds ...\n");
> /* For both, touch all bytes in the actual member size. */
> --
> 2.25.1
>

--
Kees Cook

2022-01-22 00:32:29

by Dan Carpenter

Subject: Re: [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

Acked-by: Dan Carpenter <[email protected]>

regards,
dan carpenter