[PATCH] kernel: relay: Improve exception handling in relay_create_buf()

[PATCH] kernel: relay: Improve exception handling in relay_create_buf()

[Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Sun, 31 Dec 2023 10:26:25 +0100

The kfree() function was called in one case by
the relay_create_buf() function during error handling
even if the passed data structure member contained a null pointer.
This issue was detected by using the Coccinelle software.

Thus use another label.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 kernel/relay.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/relay.c b/kernel/relay.c
index a8e90e98bf2c..b8c06305213d 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -161,14 +161,15 @@ static struct rchan_buf *relay_create_buf(struct rchan *chan)

 	buf->start = relay_alloc_buf(buf, &chan->alloc_size);
 	if (!buf->start)
-		goto free_buf;
+		goto free_padding;

 	buf->chan = chan;
 	kref_get(&buf->chan->kref);
 	return buf;

-free_buf:
+free_padding:
 	kfree(buf->padding);
+free_buf:
 	kfree(buf);
 	return NULL;
 }
--
2.43.0

Re: [PATCH] kernel: relay: Improve exception handling in relay_create_buf()

[Andrew Morton]

On Sun, 31 Dec 2023 10:38:10 +0100 Markus Elfring <Markus.Elfring@web.de> wrote:

> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Sun, 31 Dec 2023 10:26:25 +0100
> 
> The kfree() function was called in one case by
> the relay_create_buf() function during error handling
> even if the passed data structure member contained a null pointer.
> This issue was detected by using the Coccinelle software.
> 
> Thus use another label.
> 
> ...
>
> --- a/kernel/relay.c
> +++ b/kernel/relay.c
> @@ -161,14 +161,15 @@ static struct rchan_buf *relay_create_buf(struct rchan *chan)
> 
>  	buf->start = relay_alloc_buf(buf, &chan->alloc_size);
>  	if (!buf->start)
> -		goto free_buf;
> +		goto free_padding;
> 
>  	buf->chan = chan;
>  	kref_get(&buf->chan->kref);
>  	return buf;
> 
> -free_buf:
> +free_padding:
>  	kfree(buf->padding);
> +free_buf:
>  	kfree(buf);
>  	return NULL;
>  }

kfree(NULL) is an OK thing to do, and is a well-known pattern.  Can we
arrange for Coccinelle to understand this?