[syzbot ci] Re: rtnetlink: RTNL avoidance in rtnl_getlink()

[syzbot ci]

syzbot ci has tested the following series

[v1] rtnetlink: RTNL avoidance in rtnl_getlink()
https://lore.kernel.org/all/20260518100134.8...@google.com
* [PATCH net-next 1/2] rtnetlink: use nla_nest_end_safe() in rtnl_fill_prop_list()
* [PATCH net-next 2/2] rtnetlink: do not acquire RTNL for RTM_GETLINK with RTEXT_FILTER_NAME_ONLY

and found the following issue:
WARNING in rtnl_fill_ifinfo

Full report is available here:
https://ci.syzbot.org/series/c0efec5e-90ce-4ba2-8383-16d7bc172521

***

WARNING in rtnl_fill_ifinfo

tree: net-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base: 627ac78f2741e2ebd2225e2e953b6964a8a9182f
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/9507e45e-17a8-457b-a47d-5229f306e1f1/config
syz repro: https://ci.syzbot.org/findings/e56b032e-6444-4682-b577-34e22399b7cc/syz_repro

------------[ cut here ]------------
RTNL: assertion failed at net/core/rtnetlink.c (2071)
WARNING: net/core/rtnetlink.c:2071 at rtnl_fill_ifinfo+0xc73/0x2770 net/core/rtnetlink.c:2071, CPU#1: syz.1.18/5818
Modules linked in:
CPU: 1 UID: 0 PID: 5818 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:rtnl_fill_ifinfo+0xc7f/0x2770 net/core/rtnetlink.c:2071
Code: 5a 41 f8 45 85 f6 74 2c e8 be 55 41 f8 e9 91 fc ff ff e8 b4 55 41 f8 48 8d 3d 9d af bb 06 48 c7 c6 40 1c de 8c ba 17 08 00 00 <67> 48 0f b9 3a e9 5d f4 ff ff 48 8d 8c 24 00 02 00 00 48 8b 44 24
RSP: 0018:ffffc90003bcee40 EFLAGS: 00010293
RAX: ffffffff89846eac RBX: 1ffff92000779dd4 RCX: ffff88816b500000
RDX: 0000000000000817 RSI: ffffffff8cde1c40 RDI: ffffffff90401e50
RBP: ffffc90003bcf118 R08: ffffffff8fdd1227 R09: 1ffffffff1fba244
R10: dffffc0000000000 R11: fffffbfff1fba245 R12: 0000000000000010
R13: 0000000000000003 R14: 1ffff92000779dd4 R15: ffff88816b898000
FS: 00007f293800b6c0(0000) GS:ffff8882a927a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2937072780 CR3: 000000016a7d4000 CR4: 00000000000006f0
Call Trace:
<TASK>
rtnl_getlink+0xce4/0x10d0 net/core/rtnetlink.c:4267
rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:7042
netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2551
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x75c/0x8e0 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1895
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
__sys_sendmsg net/socket.c:2784 [inline]
__do_sys_sendmsg net/socket.c:2789 [inline]
__se_sys_sendmsg net/socket.c:2787 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f293719ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f293800b028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f2937415fa0 RCX: 00007f293719ce59
RDX: 0000000000000004 RSI: 0000200000000ac0 RDI: 0000000000000003
RBP: 00007f2937232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2937416038 R14: 00007f2937415fa0 R15: 00007ffffb498538
</TASK>
----------------
Code disassembly (best guess):
0: 5a pop %rdx
1: 41 f8 rex.B clc
3: 45 85 f6 test %r14d,%r14d
6: 74 2c je 0x34
8: e8 be 55 41 f8 call 0xf84155cb
d: e9 91 fc ff ff jmp 0xfffffca3
12: e8 b4 55 41 f8 call 0xf84155cb
17: 48 8d 3d 9d af bb 06 lea 0x6bbaf9d(%rip),%rdi # 0x6bbafbb
1e: 48 c7 c6 40 1c de 8c mov $0xffffffff8cde1c40,%rsi
25: ba 17 08 00 00 mov $0x817,%edx
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: e9 5d f4 ff ff jmp 0xfffff491
34: 48 8d 8c 24 00 02 00 lea 0x200(%rsp),%rcx
3b: 00
3c: 48 rex.W
3d: 8b .byte 0x8b
3e: 44 rex.R
3f: 24 .byte 0x24


***

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: syz...@syzkaller.appspotmail.com

---
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[Eric Dumazet]

On Mon, May 18, 2026 at 9:38 AM syzbot ci
<syzbot+ci0e3...@syzkaller.appspotmail.com> wrote:
>
> syzbot ci has tested the following series
>
> [v1] rtnetlink: RTNL avoidance in rtnl_getlink()
> https://lore.kernel.org/all/20260518100134.8...@google.com
> * [PATCH net-next 1/2] rtnetlink: use nla_nest_end_safe() in rtnl_fill_prop_list()
> * [PATCH net-next 2/2] rtnetlink: do not acquire RTNL for RTM_GETLINK with RTEXT_FILTER_NAME_ONLY
>
> and found the following issue:
> WARNING in rtnl_fill_ifinfo
>
> Full report is available here:
> https://ci.syzbot.org/series/c0efec5e-90ce-4ba2-8383-16d7bc172521
>
> ***
>

Hmmm. I thought I moved the ASSERT_RTNL(), but apparently this part was lost.