[PATCH] kernel/cpu: fix: use scnprintf or sprintf.

[PATCH] kernel/cpu: fix: use scnprintf or sprintf.

[YANG LI]

The snprintf() function returns the number of characters which would
have been printed if there were enough space, but the scnprintf()
returns the number of characters which were actually printed. If the
buffer is not large enough, then using snprintf() would result in a
read overflow and an information leak.

Signed-off-by: YANG LI <abaci-bugfix@linux.alibaba.com>
Reported-by: Abaci <abaci@linux.alibaba.com>
---
 kernel/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 4e11e91..c123741 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2345,7 +2345,7 @@ static ssize_t show_cpuhp_states(struct device *dev,
 {
 	const char *state = smt_states[cpu_smt_control];
 
-	return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
+	return scnprintf(buf, PAGE_SIZE - 2, "%s\n", state);
 }
 
 static ssize_t
-- 
1.8.3.1

Re: [PATCH] kernel/cpu: fix: use scnprintf or sprintf.

[Qais Yousef]

Hi Yang

'or sprintf' in the subject line doesn't make much sense for what's done in
this patch. Perhaps you meant "Use scnprintf instead of snprintf"?

On 12/22/20 17:11, YANG LI wrote:
> The snprintf() function returns the number of characters which would
> have been printed if there were enough space, but the scnprintf()
> returns the number of characters which were actually printed. If the
> buffer is not large enough, then using snprintf() would result in a
> read overflow and an information leak.
> 
> Signed-off-by: YANG LI <abaci-bugfix@linux.alibaba.com>
> Reported-by: Abaci <abaci@linux.alibaba.com>

Two different yet very similar email addresses, it seems both are you? The
Reported-by is unnecessary.

> ---
>  kernel/cpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 4e11e91..c123741 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -2345,7 +2345,7 @@ static ssize_t show_cpuhp_states(struct device *dev,
>  {
>  	const char *state = smt_states[cpu_smt_control];
>  
> -	return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
> +	return scnprintf(buf, PAGE_SIZE - 2, "%s\n", state);

show_cpuhp_states() doesn't have snprintf() in Linus' master. Which tree is
this based on?

I can see two snprintf() in cpu.c, show_smt_active/control().

Mind resend to fix them both?

Thanks

--
Qais Yousef