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List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6602:1595:b0:881:99eb:e212 with SMTP id ca18e2360f4ac-883f12550d5mr771824239f.9.1754681630334; Fri, 08 Aug 2025 12:33:50 -0700 (PDT) Date: Fri, 08 Aug 2025 12:33:50 -0700 In-Reply-To: <20250808153721.261334-1-simon.schippers@tu-dortmund.de> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6896511e.050a0220.7f033.0088.GAE@google.com> Subject: [syzbot ci] Re: TUN/TAP: Improving throughput and latency by avoiding SKB drops From: syzbot ci To: jasowang@redhat.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, simon.schippers@tu-dortmund.de, tim.gebauer@tu-dortmund.de, willemdebruijn.kernel@gmail.com Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] TUN/TAP: Improving throughput and latency by avoiding SKB drops https://lore.kernel.org/all/20250808153721.261334-1-simon.schippers@tu-dortmund.de * [PATCH net] TUN/TAP: Improving throughput and latency by avoiding SKB drops and found the following issue: general protection fault in tun_net_xmit Full report is available here: https://ci.syzbot.org/series/4a9dd6ad-3c81-4957-b447-4d1e8e9ee7a2 *** general protection fault in tun_net_xmit tree: net URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git base: ae633388cae349886f1a3cfb27aa092854b24c1b arch: amd64 compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 config: https://ci.syzbot.org/builds/f35af9e4-44af-4a13-8842-d9d36ecb06e7/config C repro: https://ci.syzbot.org/findings/e400bf02-40dc-43bb-8c15-d21b7ecb7304/c_repro syz repro: https://ci.syzbot.org/findings/e400bf02-40dc-43bb-8c15-d21b7ecb7304/syz_repro Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted 6.16.0-syzkaller-06620-gae633388cae3-dirty #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:__ptr_ring_full include/linux/ptr_ring.h:51 [inline] RIP: 0010:ptr_ring_full include/linux/ptr_ring.h:59 [inline] RIP: 0010:tun_net_xmit+0x3ee/0x19c0 drivers/net/tun.c:1026 Code: 54 24 18 48 89 d0 48 c1 e8 03 48 89 44 24 58 42 0f b6 04 28 84 c0 0f 85 f9 11 00 00 48 63 02 48 8d 1c c3 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 d3 0f ac fb 48 8b 1b 48 8b 7c 24 RSP: 0018:ffffc900000f6f00 EFLAGS: 00010202 RAX: 0000000000000002 RBX: 0000000000000010 RCX: dffffc0000000000 RDX: ffff88811bf90940 RSI: 0000000000000004 RDI: ffffc900000f6e80 RBP: ffffc900000f7050 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff5200001edd0 R12: 0000000000000000 R13: dffffc0000000000 R14: ffff8881054c8000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881a3c80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000002280 CR3: 0000000110b70000 CR4: 00000000000006f0 Call Trace: __netdev_start_xmit include/linux/netdevice.h:5219 [inline] netdev_start_xmit include/linux/netdevice.h:5228 [inline] xmit_one net/core/dev.c:3827 [inline] dev_hard_start_xmit+0x2d7/0x830 net/core/dev.c:3843 sch_direct_xmit+0x241/0x4b0 net/sched/sch_generic.c:344 __dev_xmit_skb net/core/dev.c:4102 [inline] __dev_queue_xmit+0x1857/0x3b50 net/core/dev.c:4679 neigh_output include/net/neighbour.h:547 [inline] ip6_finish_output2+0x11fe/0x16a0 net/ipv6/ip6_output.c:141 NF_HOOK include/linux/netfilter.h:318 [inline] ndisc_send_skb+0xb54/0x1440 net/ipv6/ndisc.c:512 addrconf_dad_completed+0x7ae/0xd60 net/ipv6/addrconf.c:4360 addrconf_dad_work+0xc36/0x14b0 net/ipv6/addrconf.c:-1 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x711/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:__ptr_ring_full include/linux/ptr_ring.h:51 [inline] RIP: 0010:ptr_ring_full include/linux/ptr_ring.h:59 [inline] RIP: 0010:tun_net_xmit+0x3ee/0x19c0 drivers/net/tun.c:1026 Code: 54 24 18 48 89 d0 48 c1 e8 03 48 89 44 24 58 42 0f b6 04 28 84 c0 0f 85 f9 11 00 00 48 63 02 48 8d 1c c3 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 d3 0f ac fb 48 8b 1b 48 8b 7c 24 RSP: 0018:ffffc900000f6f00 EFLAGS: 00010202 RAX: 0000000000000002 RBX: 0000000000000010 RCX: dffffc0000000000 RDX: ffff88811bf90940 RSI: 0000000000000004 RDI: ffffc900000f6e80 RBP: ffffc900000f7050 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffff5200001edd0 R12: 0000000000000000 R13: dffffc0000000000 R14: ffff8881054c8000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881a3c80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000002280 CR3: 0000000110b70000 CR4: 00000000000006f0 ---------------- Code disassembly (best guess): 0: 54 push %rsp 1: 24 18 and $0x18,%al 3: 48 89 d0 mov %rdx,%rax 6: 48 c1 e8 03 shr $0x3,%rax a: 48 89 44 24 58 mov %rax,0x58(%rsp) f: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax 14: 84 c0 test %al,%al 16: 0f 85 f9 11 00 00 jne 0x1215 1c: 48 63 02 movslq (%rdx),%rax 1f: 48 8d 1c c3 lea (%rbx,%rax,8),%rbx 23: 48 89 d8 mov %rbx,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction 2f: 74 08 je 0x39 31: 48 89 df mov %rbx,%rdi 34: e8 d3 0f ac fb call 0xfbac100c 39: 48 8b 1b mov (%rbx),%rbx 3c: 48 rex.W 3d: 8b .byte 0x8b 3e: 7c 24 jl 0x64 *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com.