Re: [syzbot] [bpf?] WARNING in dev_xdp_install

syzbot
2025-03-28T23:26:54Z

> On 03/28, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 1a9239bb4253 Merge tag 'net-next-6.15' of git://git.kernel..
>> git tree: upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=17989bb0580000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=d48017cf0c2458bf
>> dashboard link: https://syzkaller.appspot.com/bug?extid=08936936fe8132f91f1a
>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/0795c9a2c8ce/disk-1a9239bb.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/dfe4e652ed32/vmlinux-1a9239bb.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/34deb7756b26/bzImage-1a9239bb.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+08936936fe8132f91f1a@syzkaller.appspotmail.com
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 1 PID: 8456 at ./include/net/netdev_lock.h:54 netdev_ops_assert_locked include/net/netdev_lock.h:54 [inline]
>> WARNING: CPU: 1 PID: 8456 at ./include/net/netdev_lock.h:54 dev_xdp_install+0x610/0x9b0 net/core/dev.c:9911
>> Modules linked in:
>> CPU: 1 UID: 0 PID: 8456 Comm: syz.5.847 Not tainted 6.14.0-syzkaller-05877-g1a9239bb4253 #0 PREEMPT(full)
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
>> RIP: 0010:netdev_ops_assert_locked include/net/netdev_lock.h:54 [inline]
>> RIP: 0010:dev_xdp_install+0x610/0x9b0 net/core/dev.c:9911
>> Code: 8d bc 24 28 0d 00 00 be ff ff ff ff e8 69 c5 26 02 31 ff 89 c5 89 c6 e8 0e af 81 f8 85 ed 0f 85 59 fb ff ff e8 d1 b3 81 f8 90 <0f> 0b 90 e9 4b fb ff ff e8 c3 b3 81 f8 49 8d bc 24 28 0d 00 00 be
>> RSP: 0018:ffffc9001f13f950 EFLAGS: 00010287
>> RAX: 000000000000023c RBX: ffff888059e8ccbd RCX: ffffc9000da1b000
>> RDX: 0000000000080000 RSI: ffffffff89395ebf RDI: 0000000000000005
>> RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff888059e8c000
>> R13: ffffffff870484d0 R14: ffffc9000ec3f000 R15: 0000000000000001
>> FS: 00007f6e99bf66c0(0000) GS:ffff888124b41000(0000) knlGS:0000000000000000
>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 000000110c2f3eb0 CR3: 000000007f4ec000 CR4: 0000000000350ef0
>> Call Trace:
>> <TASK>
>> dev_xdp_attach+0x6d1/0x16a0 net/core/dev.c:10094
>> dev_xdp_attach_link net/core/dev.c:10113 [inline]
>> bpf_xdp_link_attach+0x2c5/0x680 net/core/dev.c:10287
>> link_create kernel/bpf/syscall.c:5379 [inline]
>> __sys_bpf+0x1bc7/0x4c80 kernel/bpf/syscall.c:5865
>> __do_sys_bpf kernel/bpf/syscall.c:5902 [inline]
>> __se_sys_bpf kernel/bpf/syscall.c:5900 [inline]
>> __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5900
>> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>> do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> RIP: 0033:0x7f6e9bd8d169
>
> #syz test

This crash does not have a reproducer. I cannot test it.

>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 87cba93fa59f..534eda336f8d 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -10336,7 +10336,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> goto unlock;
> }
>
> + netdev_lock_ops(dev);
> err = dev_xdp_attach_link(dev, &extack, link);
> + netdev_unlock_ops(dev);
> rtnl_unlock();
>
> if (err) {