linux-kernel - Re: [syzbot] [bpf?] WARNING in dev_xdp

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Message-ID: <Z-cwOkotpxeSxirT@mini-arch>
Date: Fri, 28 Mar 2025 16:26:50 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: syzbot <syzbot+08936936fe8132f91f1a@...kaller.appspotmail.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
	netdev@...r.kernel.org, kuba@...nel.org, daniel@...earbox.net,
	eddyz87@...il.com, haoluo@...gle.com, john.fastabend@...il.com,
	jolsa@...nel.org, kpsingh@...nel.org, linux-kernel@...r.kernel.org,
	martin.lau@...ux.dev, sdf@...ichev.me, song@...nel.org,
	syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] WARNING in dev_xdp_install

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@...kaller.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

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) {