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

Martin Schiller
2026-03-27T08:50:53Z

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>