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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Shuangpeng Bai , oe-linux-nfc@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [BUG] nfc: KASAN: slab-use-after-free in nfc_llcp_rx_skb Date: Tue, 18 Aug 2026 20:20:45 -0400 Message-ID: <20260819002050.3476701-1-shuangpeng.kernel@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: oe-linux-nfc@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Kernel Maintainers, I hit the following report while testing current upstream kernel: KASAN: slab-use-after-free in nfc_llcp_rx_skb on commit: 3609fa95fb0f2c1b099e69e56634edb8fc03f87c (2026-01-04) The reproducer and .config files are here. https://gist.github.com/shuangpengbai/70e3bdc241dbd675970fe89f30f0b84e I'm happy to test debug patches or provide additional information. Reported-by: Shuangpeng Bai Decoded source path: use: net/nfc/llcp_core.c:1185 in nfc_llcp_recv_disc(), reading sk->sk_state after nfc_llcp_sock_put() at line 1182; DISC dispatch is called from net/nfc/llcp_core.c:1483 in nfc_llcp_rx_skb(). free: concurrent socket release drops the final reference through net/nfc/llcp_sock.c:646 sock_put(), then sk_free() releases the same struct nfc_llcp_sock allocation. [ 81.172360][ T830] BUG: KASAN: slab-use-after-free in nfc_llcp_rx_skb (net/nfc/llcp_core.c:? net/nfc/llcp_core.c:1483) [ 81.173044][ T830] Read of size 1 at addr ffff888119369812 by task kworker/1:2/830 [ 81.173940][ T830] Tainted: [B]=BAD_PAGE, [W]=WARN [ 81.173941][ T830] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 81.173943][ T830] Workqueue: events nfc_llcp_rx_work [ 81.173946][ T830] Call Trace: [ 81.173947][ T830] [ 81.173952][ T830] print_report (mm/kasan/report.c:379 mm/kasan/report.c:482) [ 81.173959][ T830] kasan_report (mm/kasan/report.c:597) [ 81.173965][ T830] nfc_llcp_rx_skb (net/nfc/llcp_core.c:? net/nfc/llcp_core.c:1483) [ 81.173973][ T830] nfc_llcp_rx_work (net/nfc/llcp_core.c:1533) [ 81.173976][ T830] process_scheduled_works (kernel/workqueue.c:3262 kernel/workqueue.c:3340) [ 81.173980][ T830] worker_thread (./include/linux/list.h:381 kernel/workqueue.c:946 kernel/workqueue.c:3422) [ 81.173984][ T830] kthread (kernel/kthread.c:465) [ 81.174000][ T830] ret_from_fork (archkernel/process.c:164) [ 81.174011][ T830] ret_from_fork_asm (arch/x86/entry/entry_64.S:256) [ 81.174014][ T830] [ 81.187221][ T830] Allocated by task 4409 on cpu 1 at 75.384100s: [ 81.188593][ T830] __kmalloc_noprof (mm/slub.c:5658 mm/slub.c:5669) [ 81.189018][ T830] sk_prot_alloc (./include/linux/slab.h:961 net/core/sock.c:2245) [ 81.189420][ T830] sk_alloc (net/core/sock.c:2301) [ 81.189779][ T830] nfc_llcp_sock_alloc (net/nfc/llcp_sock.c:979) [ 81.190222][ T830] nfc_llcp_rx_skb (net/nfc/llcp_core.c:971 net/nfc/llcp_core.c:1478) [ 81.190656][ T830] nfc_llcp_rx_work (net/nfc/llcp_core.c:1533) [ 81.193365][ T830] Freed by task 31 on cpu 196609 at 78.490492s: [ 81.195183][ T830] kfree (mm/slub.c:6670 mm/slub.c:6878) [ 81.195531][ T830] __sk_destruct (net/core/sock.c:2285 net/core/sock.c:2384) [ 81.195937][ T830] nfc_llcp_rx_skb (.net/sock.h:? net/nfc/llcp_core.c:233 net/nfc/llcp_core.c:1194 net/nfc/llcp_core.c:1483) [ 81.196379][ T830] nfc_llcp_rx_work (net/nfc/llcp_core.c:1533) [ 81.199084][ T830] The buggy address belongs to the object at ffff888119369800 [ 81.199084][ T830] which belongs to the cache kmalloc-1k of size 1024 [ 81.200297][ T830] The buggy address is located 18 bytes inside of [ 81.200297][ T830] freed 1024-byte region [ffff888119369800, ffff888119369c00) Best, Shuangpeng