Re: [BUG] NFC: slab-use-after-free in _raw_spin_lock_irqsave

[Eric Dumazet]

On Wed, Aug 19, 2026 at 7:00 AM Shuangpeng Bai
<shuangpeng.kernel@xxxxxxxxx> wrote:
>
> Hi Kernel Maintainers,
>
> I hit the following report while testing current upstream kernel:
>
> KASAN: slab-use-after-free in _raw_spin_lock_irqsave
>
> on commit: 3aa1dcaa4f6f5ae08936491e08bd456f331f2d40 (2026-08-13)
>
> To help trigger the bug more reliably, we applied a minimal diagnostic patch
> that only adds delays and print statements.
>
> The reproducer and .config files are here.
> https://gist.github.com/shuangpengbai/f7dab4725e2a2d57b1d302714c93c549
>
> I'm happy to test debug patches or provide additional information.

Thanks for the report, could you test adding one skb_set_owner_w()
after the skb_copy() in nfc_llcp_tx_work() ?

Something like this (untested, not compiled) patch.

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index cac1b5487064d0c5b4966bb6a75aa26e67131049..49cb632268c0c2841e3b44dde124c7966267b709
100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -786,8 +786,11 @@ static void nfc_llcp_tx_work(struct work_struct *work)
                        print_hex_dump_debug("LLCP Tx: ", DUMP_PREFIX_OFFSET,
                                             16, 1, skb->data, skb->len, true);

-                       if (ptype == LLCP_PDU_I)
+                       if (ptype == LLCP_PDU_I) {
                                copy_skb = skb_copy(skb, GFP_ATOMIC);
+                               if (copy_skb)
+                                       skb_set_owner_w(copy_skb, sk);
+                       }

                        __net_timestamp(skb);