[PATCH net] net/x25: Fix overflow when accumulating packets

[PATCH net] net/x25: Fix overflow when accumulating packets

[Martin Schiller]

Add a check to ensure that `x25_sock.fraglen` does not overflow.

The `fraglen` also needs to be resetted when purging `fragment_queue` in
`x25_clear_queues()`.

Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
---
 net/x25/x25_in.c   | 6 ++++++
 net/x25/x25_subr.c | 1 +
 2 files changed, 7 insertions(+)

diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
index b981a4828d08c2e6676749a06035910eab01e6cd..1603238d6fff73090ef10b5fd11387b3e7f017a2 100644
--- a/net/x25/x25_in.c
+++ b/net/x25/x25_in.c
@@ -34,6 +34,12 @@ static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
 	struct sk_buff *skbo, *skbn = skb;
 	struct x25_sock *x25 = x25_sk(sk);
 
+	/* make sure we don't overflow */
+	if (x25->fraglen + skb->len > sizeof(x25->fraglen)) {
+		kfree_skb(skb);
+		return 1;
+	}
+
 	if (more) {
 		x25->fraglen += skb->len;
 		skb_queue_tail(&x25->fragment_queue, skb);
diff --git a/net/x25/x25_subr.c b/net/x25/x25_subr.c
index 0285aaa1e93c17233748d38eef6d8b5c6059b67a..159708d9ad20cb2e6db24ead67daf1e9d6258f64 100644
--- a/net/x25/x25_subr.c
+++ b/net/x25/x25_subr.c
@@ -40,6 +40,7 @@ void x25_clear_queues(struct sock *sk)
 	skb_queue_purge(&x25->interrupt_in_queue);
 	skb_queue_purge(&x25->interrupt_out_queue);
 	skb_queue_purge(&x25->fragment_queue);
+	x25->fraglen = 0;
 }
 
 

---
base-commit: 4ae97cae07e15d41e5c0ebabba64c6eefdeb0bbe
change-id: 20260325-x25_fraglen-8fc240d1edd3

Best regards,
-- 
Martin Schiller <ms@dev.tdt.de>

Re: [PATCH net] net/x25: Fix overflow when accumulating packets

[Martin Schiller]

On 2026-03-27 09:30, Martin Schiller wrote:
> Add a check to ensure that `x25_sock.fraglen` does not overflow.
> 
> The `fraglen` also needs to be resetted when purging `fragment_queue` 
> in
> `x25_clear_queues()`.
> 
> Reported-by: Yiming Qian <yimingqian591@gmail.com>
> Signed-off-by: Martin Schiller <ms@dev.tdt.de>
> ---
>  net/x25/x25_in.c   | 6 ++++++
>  net/x25/x25_subr.c | 1 +
>  2 files changed, 7 insertions(+)
> 
> diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
> index
> b981a4828d08c2e6676749a06035910eab01e6cd..1603238d6fff73090ef10b5fd11387b3e7f017a2
> 100644
> --- a/net/x25/x25_in.c
> +++ b/net/x25/x25_in.c
> @@ -34,6 +34,12 @@ static int x25_queue_rx_frame(struct sock *sk,
> struct sk_buff *skb, int more)
>  	struct sk_buff *skbo, *skbn = skb;
>  	struct x25_sock *x25 = x25_sk(sk);
> 
> +	/* make sure we don't overflow */
> +	if (x25->fraglen + skb->len > sizeof(x25->fraglen)) {

Please ignore this patch. I'll send a V2 without that
"sizeof()" nonsense in a moment.

> +		kfree_skb(skb);
> +		return 1;
> +	}
> +
>  	if (more) {
>  		x25->fraglen += skb->len;
>  		skb_queue_tail(&x25->fragment_queue, skb);
> diff --git a/net/x25/x25_subr.c b/net/x25/x25_subr.c
> index
> 0285aaa1e93c17233748d38eef6d8b5c6059b67a..159708d9ad20cb2e6db24ead67daf1e9d6258f64
> 100644
> --- a/net/x25/x25_subr.c
> +++ b/net/x25/x25_subr.c
> @@ -40,6 +40,7 @@ void x25_clear_queues(struct sock *sk)
>  	skb_queue_purge(&x25->interrupt_in_queue);
>  	skb_queue_purge(&x25->interrupt_out_queue);
>  	skb_queue_purge(&x25->fragment_queue);
> +	x25->fraglen = 0;
>  }
> 
> 
> 
> ---
> base-commit: 4ae97cae07e15d41e5c0ebabba64c6eefdeb0bbe
> change-id: 20260325-x25_fraglen-8fc240d1edd3
> 
> Best regards,