In tls_handshake_accept(), a netlink message is allocated using
genlmsg_new(). In the error handling path, genlmsg_cancel() is called
to cancel the message construction, but the message itself is not freed.
This leads to a memory leak.

Fix this by calling nlmsg_free() in the error path after genlmsg_cancel()
to release the allocated memory.

Fixes: 2fd5532044a89 ("net/handshake: Add a kernel API for requesting a TLSv1.3 handshake")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
---
 net/handshake/tlshd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/handshake/tlshd.c b/net/handshake/tlshd.c
index 081093dfd553..8f9532a15f43 100644
--- a/net/handshake/tlshd.c
+++ b/net/handshake/tlshd.c
@@ -259,6 +259,7 @@ static int tls_handshake_accept(struct handshake_req *req,
 
 out_cancel:
 	genlmsg_cancel(msg, hdr);
+	nlmsg_free(msg);
 out:
 	return ret;
 }
-- 
2.34.1

On Thu, Nov 06, 2025 at 02:45:11PM +0000, Zilin Guan wrote:
> In tls_handshake_accept(), a netlink message is allocated using
> genlmsg_new(). In the error handling path, genlmsg_cancel() is called
> to cancel the message construction, but the message itself is not freed.
> This leads to a memory leak.
> 
> Fix this by calling nlmsg_free() in the error path after genlmsg_cancel()
> to release the allocated memory.
> 
> Fixes: 2fd5532044a89 ("net/handshake: Add a kernel API for requesting a TLSv1.3 handshake")
> Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
> ---
>  net/handshake/tlshd.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/handshake/tlshd.c b/net/handshake/tlshd.c
> index 081093dfd553..8f9532a15f43 100644
> --- a/net/handshake/tlshd.c
> +++ b/net/handshake/tlshd.c
> @@ -259,6 +259,7 @@ static int tls_handshake_accept(struct handshake_req *req,
>  
>  out_cancel:
>  	genlmsg_cancel(msg, hdr);

Hi Zilin Guan,

I don't think genlmsg_cancel() is necessary if msg is freed on the next line.
If so, I suggest removing it, and renaming out_cancel accordingly.

> +	nlmsg_free(msg);
>  out:
>  	return ret;
>  }
> -- 
> 2.34.1
>

On Fri, Nov 07, 2025 at 10:17:09AM +0000, Simon Horman wrote:
> On Thu, Nov 06, 2025 at 02:45:11PM +0000, Zilin Guan wrote:
> > In tls_handshake_accept(), a netlink message is allocated using
> > genlmsg_new(). In the error handling path, genlmsg_cancel() is called
> > to cancel the message construction, but the message itself is not freed.
> > This leads to a memory leak.
> > 
> > Fix this by calling nlmsg_free() in the error path after genlmsg_cancel()
> > to release the allocated memory.
> > 
> > Fixes: 2fd5532044a89 ("net/handshake: Add a kernel API for requesting a TLSv1.3 handshake")
> > Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
> > ---
> >  net/handshake/tlshd.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/net/handshake/tlshd.c b/net/handshake/tlshd.c
> > index 081093dfd553..8f9532a15f43 100644
> > --- a/net/handshake/tlshd.c
> > +++ b/net/handshake/tlshd.c
> > @@ -259,6 +259,7 @@ static int tls_handshake_accept(struct handshake_req *req,
> >  
> >  out_cancel:
> >  	genlmsg_cancel(msg, hdr);
> 
> Hi Zilin Guan,
> 
> I don't think genlmsg_cancel() is necessary if msg is freed on the next line.
> If so, I suggest removing it, and renaming out_cancel accordingly.
>
> > +	nlmsg_free(msg);
> >  out:
> >  	return ret;
> >  }
> > -- 
> > 2.34.1
> > 

Hi Simon,

Thanks for your review.

I followed the pattern I observed in other parts of the kernel, for example,
in cifs_swn_send_register_message() in fs/smb/client/cifs_swn.c, where
genlmsg_cancel() is also called before nlmsg_free() in the error path.

My understanding is that this is the proper way to unwind the message
construction before freeing it.

If you still believe it's unnecessary, I am happy to send a v2 patch
to remove it.

Best regards,
Zilin Guan

On 11/6/25 9:45 AM, Zilin Guan wrote:
> In tls_handshake_accept(), a netlink message is allocated using
> genlmsg_new(). In the error handling path, genlmsg_cancel() is called
> to cancel the message construction, but the message itself is not freed.
> This leads to a memory leak.
> 
> Fix this by calling nlmsg_free() in the error path after genlmsg_cancel()
> to release the allocated memory.
> 
> Fixes: 2fd5532044a89 ("net/handshake: Add a kernel API for requesting a TLSv1.3 handshake")
> Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
> ---
>  net/handshake/tlshd.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/handshake/tlshd.c b/net/handshake/tlshd.c
> index 081093dfd553..8f9532a15f43 100644
> --- a/net/handshake/tlshd.c
> +++ b/net/handshake/tlshd.c
> @@ -259,6 +259,7 @@ static int tls_handshake_accept(struct handshake_req *req,
>  
>  out_cancel:
>  	genlmsg_cancel(msg, hdr);
> +	nlmsg_free(msg);
>  out:
>  	return ret;
>  }

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>

-- 
Chuck Lever