* [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc
@ 2022-01-20 9:29 Jiasheng Jiang
2022-01-20 18:14 ` Kees Cook
2022-01-21 4:41 ` Dan Carpenter
0 siblings, 2 replies; 3+ messages in thread
From: Jiasheng Jiang @ 2022-01-20 9:29 UTC (permalink / raw)
To: gregkh; +Cc: keescook, dan.carpenter, arnd, linux-kernel, 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 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.
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
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc
2022-01-20 9:29 [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc Jiasheng Jiang
@ 2022-01-20 18:14 ` Kees Cook
2022-01-21 4:41 ` Dan Carpenter
1 sibling, 0 replies; 3+ messages in thread
From: Kees Cook @ 2022-01-20 18:14 UTC (permalink / raw)
To: Jiasheng Jiang; +Cc: gregkh, dan.carpenter, arnd, linux-kernel
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 <jiasheng@iscas.ac.cn>
> ---
> 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 <keescook@chromium.org>
>
> 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
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc
2022-01-20 9:29 [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc Jiasheng Jiang
2022-01-20 18:14 ` Kees Cook
@ 2022-01-21 4:41 ` Dan Carpenter
1 sibling, 0 replies; 3+ messages in thread
From: Dan Carpenter @ 2022-01-21 4:41 UTC (permalink / raw)
To: Jiasheng Jiang; +Cc: gregkh, keescook, arnd, linux-kernel
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-01-20 9:29 [PATCH v4] lkdtm/bugs: Check for the NULL pointer after calling kmalloc Jiasheng Jiang
2022-01-20 18:14 ` Kees Cook
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