[PATCH v3] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

[PATCH v3] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

[Jiasheng Jiang]

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 explicitly yell about the memory failure and then
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 <jiasheng@iscas.ac.cn>
---
Changelog

v1 -> v2

* Change 1. Add the kfree if fails.

v2 -> v3

* Change 1. Add pr_err if fails.
---
 drivers/misc/lkdtm/bugs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index f4cb94a9aa9c..c64ab6f387eb 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -325,6 +325,12 @@ 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) {
+		pr_err("FAIL: could not allocate required buffers!\n");
+		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

Re: [PATCH v3] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

[Greg KH]

On Thu, Jan 20, 2022 at 09:25:51AM +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 explicitly yell about the memory failure and then
> 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 <jiasheng@iscas.ac.cn>
> ---
> Changelog
> 
> v1 -> v2
> 
> * Change 1. Add the kfree if fails.
> 
> v2 -> v3
> 
> * Change 1. Add pr_err if fails.
> ---
>  drivers/misc/lkdtm/bugs.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
> index f4cb94a9aa9c..c64ab6f387eb 100644
> --- a/drivers/misc/lkdtm/bugs.c
> +++ b/drivers/misc/lkdtm/bugs.c
> @@ -325,6 +325,12 @@ 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) {
> +		pr_err("FAIL: could not allocate required buffers!\n");

As was pointed out, this is now a checkpatch failure :(