[PATCH V2] lockdown: Initialize array before use

[PATCH V2] lockdown: Initialize array before use

[Tanya Agarwal]

From: Tanya Agarwal <tanyaagarwal25699@gmail.com>

The static code analysis tool "Coverity Scan" pointed the following
details out for further development considerations:
CID 1486102: Uninitialized scalar variable (UNINIT)
uninit_use_in_call: Using uninitialized value *temp when calling
strlen.

Conclusion:
Initialize array before use in lockdown_read().

Fixes: 000d388ed3bb ("security: Add a static lockdown policy LSM")
Signed-off-by: Tanya Agarwal <tanyaagarwal25699@gmail.com>
---
V2: add Fixes tag and reword commit description

Coverity Link:
https://scan7.scan.coverity.com/#/project-view/52849/11354?selectedIssue=1486102

 security/lockdown/lockdown.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index f2bdbd55aa2b..df2c8435a7a9 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -96,7 +96,7 @@ static int __init lockdown_lsm_init(void)
 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count,
 			     loff_t *ppos)
 {
-	char temp[80];
+	char temp[80] = {0};
 	int i, offset = 0;
 
 	for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
-- 
2.39.5

Re: [PATCH v2] lockdown: Initialize array before use

[Paul Moore]

On Jan  4, 2025 Tanya Agarwal <tanyaagarwal25699@gmail.com> wrote:
> 
> The static code analysis tool "Coverity Scan" pointed the following
> details out for further development considerations:
> CID 1486102: Uninitialized scalar variable (UNINIT)
> uninit_use_in_call: Using uninitialized value *temp when calling
> strlen.
> 
> Conclusion:
> Initialize array before use in lockdown_read().
> 
> Fixes: 000d388ed3bb ("security: Add a static lockdown policy LSM")
> Signed-off-by: Tanya Agarwal <tanyaagarwal25699@gmail.com>
> ---
> V2: add Fixes tag and reword commit description
> 
> Coverity Link:
> https://scan7.scan.coverity.com/#/project-view/52849/11354?selectedIssue=1486102
> 
>  security/lockdown/lockdown.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
> index f2bdbd55aa2b..df2c8435a7a9 100644
> --- a/security/lockdown/lockdown.c
> +++ b/security/lockdown/lockdown.c
> @@ -96,7 +96,7 @@ static int __init lockdown_lsm_init(void)
>  static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count,
>  			     loff_t *ppos)
>  {
> -	char temp[80];
> +	char temp[80] = {0};
>  	int i, offset = 0;

Since @temp is a string, it reads a bit better if we initialize it with
double quotes, e.g. 'char temp[80] = ""'.

This is also a case where the static analysis is a bit misleading.  The
@temp variable is uninitialized only if the @lockdown_levels array is
empty and seeing as the @lockdown_levels array is a constant array
defined in the source, this isn't a real issue we need to worry about.
However, if you wanted to fix this simply to quiet Coverity, I think
that would be okay, especially since this isn't a hot code path.

>  	for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
> -- 
> 2.39.5

--
paul-moore.com

Re: [PATCH v2] lockdown: Initialize array before use

[Tanya Agarwal]

On Sun, Jan 5, 2025 at 9:45 AM Paul Moore <paul@paul-moore.com> wrote:
>
> On Jan  4, 2025 Tanya Agarwal <tanyaagarwal25699@gmail.com> wrote:
> >

> > -     char temp[80];
> > +     char temp[80] = {0};
> >       int i, offset = 0;
>
> Since @temp is a string, it reads a bit better if we initialize it with
> double quotes, e.g. 'char temp[80] = ""'.

Hi Paul,

Thanks for the review.
I agree to change it to double quotes and will send it in a revision patch.

>
> This is also a case where the static analysis is a bit misleading.  The
> @temp variable is uninitialized only if the @lockdown_levels array is
> empty and seeing as the @lockdown_levels array is a constant array
> defined in the source, this isn't a real issue we need to worry about.
> However, if you wanted to fix this simply to quiet Coverity, I think
> that would be okay, especially since this isn't a hot code path.

I understand that is likely a false positive. However, as you
mentioned this is not a hot path, making initialization explicit could
help silence the static analyzer without any real downside.

Thanks,
Tanya

>
> >       for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
> > --
> > 2.39.5
>
> --
> paul-moore.com