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Wed, 26 Nov 2025 10:25:32 -0800 (PST) Date: Wed, 26 Nov 2025 10:25:32 -0800 In-Reply-To: <68a5c278.050a0220.3d78fd.0000.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6927461c.a70a0220.d98e3.00df.GAE@google.com> Subject: Forwarded: Re: [syzbot] [mptcp?] WARNING in subflow_data_ready (4) From: syzbot To: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org. *** Subject: Re: [syzbot] [mptcp?] WARNING in subflow_data_ready (4) Author: pabeni@redhat.com On 11/20/25 9:58 PM, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: 8e621c9a3375 Merge tag 'net-6.18-rc7' of git://git.kernel... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=12887a12580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=1cd7f786c0f5182f > dashboard link: https://syzkaller.appspot.com/bug?extid=0ff6b771b4f7a5bce83b > compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=133c9a12580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=117a2a12580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/6be75789d60e/disk-8e621c9a.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/62e7a40cfe48/vmlinux-8e621c9a.xz > kernel image: https://storage.googleapis.com/syzbot-assets/3e523caa536d/bzImage-8e621c9a.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+0ff6b771b4f7a5bce83b@syzkaller.appspotmail.com > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 15 at net/mptcp/subflow.c:1519 subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1519 > Modules linked in: > CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 > RIP: 0010:subflow_data_ready+0x40b/0x7c0 net/mptcp/subflow.c:1519 > Code: 89 ee e8 88 f8 72 f6 40 84 ed 75 21 e8 9e fd 72 f6 44 89 fe bf 07 00 00 00 e8 d1 f8 72 f6 41 83 ff 07 74 09 e8 86 fd 72 f6 90 <0f> 0b 90 e8 7d fd 72 f6 48 89 df e8 e5 ad ff ff 31 ff 89 c5 89 c6 > RSP: 0018:ffffc90000147380 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: ffff888030aa72c0 RCX: ffffffff8b4959ef > RDX: ffff88801d2cbc80 RSI: ffffffff8b4959fa RDI: 0000000000000005 > RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000007 > R10: 0000000000000004 R11: 00000d230000000c R12: ffff888033463c00 > R13: 1ffff92000028e70 R14: ffff88802f9bbc00 R15: 0000000000000004 > FS: 0000000000000000(0000) GS:ffff888124a0d000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f841c04df98 CR3: 0000000078b7e000 CR4: 00000000003526f0 > Call Trace: > > tcp_data_ready+0x110/0x550 net/ipv4/tcp_input.c:5355 > tcp_data_queue+0x1aa6/0x5000 net/ipv4/tcp_input.c:5445 > tcp_rcv_state_process+0xfb6/0x6490 net/ipv4/tcp_input.c:7159 > tcp_v4_do_rcv+0x68e/0x10a0 net/ipv4/tcp_ipv4.c:1954 > tcp_v4_rcv+0x3077/0x4db0 net/ipv4/tcp_ipv4.c:2374 > ip_protocol_deliver_rcu+0xba/0x4c0 net/ipv4/ip_input.c:205 > ip_local_deliver_finish+0x3f2/0x720 net/ipv4/ip_input.c:239 > NF_HOOK include/linux/netfilter.h:318 [inline] > NF_HOOK include/linux/netfilter.h:312 [inline] > ip_local_deliver+0x18e/0x1f0 net/ipv4/ip_input.c:260 > dst_input include/net/dst.h:474 [inline] > ip_rcv_finish net/ipv4/ip_input.c:453 [inline] > NF_HOOK include/linux/netfilter.h:318 [inline] > NF_HOOK include/linux/netfilter.h:312 [inline] > ip_rcv+0x2e0/0x600 net/ipv4/ip_input.c:573 > __netif_receive_skb_one_core+0x197/0x1e0 net/core/dev.c:6079 > __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192 > process_backlog+0x439/0x15e0 net/core/dev.c:6544 > __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7594 > napi_poll net/core/dev.c:7657 [inline] > net_rx_action+0x97f/0xef0 net/core/dev.c:7784 > handle_softirqs+0x219/0x8e0 kernel/softirq.c:622 > run_ksoftirqd kernel/softirq.c:1063 [inline] > run_ksoftirqd+0x3a/0x60 kernel/softirq.c:1055 > smpboot_thread_fn+0x3f7/0xae0 kernel/smpboot.c:160 > kthread+0x3c5/0x780 kernel/kthread.c:463 > ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > > > --- > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git main I can't repro it locally. Running a debug patch to collect more status which hopefully should help understanding the race.