net: netrom: fix memory leak in nr_output()

[PATCH] net: netrom: fix memory leak in nr_output()

Posted by Deepanshu Kartikey 2 days, 18 hours ago

When nr_output() fragments a large packet, it calls sock_alloc_send_skb()
in a loop to allocate skbs for each fragment. If this allocation fails,
the function returns without freeing the original skb that was passed in,
causing a memory leak.

Add the missing kfree_skb() call before returning on allocation failure.

Reported-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
Tested-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 net/netrom/nr_out.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c
index 5e531394a724..2b3cbceb0b52 100644
--- a/net/netrom/nr_out.c
+++ b/net/netrom/nr_out.c
@@ -43,8 +42,11 @@ void nr_output(struct sock *sk, struct sk_buff *skb)
 		frontlen = skb_headroom(skb);
 
 		while (skb->len > 0) {
-			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
			skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err);
			if (skbn == NULL) {
+				kfree_skb(skb);
 				return;
+			}
 
 			skb_reserve(skbn, frontlen);
 
-- 
2.43.0

Re: [PATCH] net: netrom: fix memory leak in nr_output()

Posted by Wang Liang 2 days, 18 hours ago

在 2025/11/29 11:42, Deepanshu Kartikey 写道:
> When nr_output() fragments a large packet, it calls sock_alloc_send_skb()


Hi!

Coincidentally, we both are working on this issue simultaneously.

 From the syz test requests:
https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58

I sended the test patch earlier, only a dozen seconds...

------
Best regards
Wang Liang

> in a loop to allocate skbs for each fragment. If this allocation fails,
> the function returns without freeing the original skb that was passed in,
> causing a memory leak.
>
> Add the missing kfree_skb() call before returning on allocation failure.
>
> Reported-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
> Tested-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---
>   net/netrom/nr_out.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c
> index 5e531394a724..2b3cbceb0b52 100644
> --- a/net/netrom/nr_out.c
> +++ b/net/netrom/nr_out.c
> @@ -43,8 +42,11 @@ void nr_output(struct sock *sk, struct sk_buff *skb)
>   		frontlen = skb_headroom(skb);
>   
>   		while (skb->len > 0) {
> -			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
> 			skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err);
> 			if (skbn == NULL) {
> +				kfree_skb(skb);
>   				return;
> +			}
>   
>   			skb_reserve(skbn, frontlen);
>