Message-ID: <6cbc88fa-1479-4e44-950a-6d3881197520@redhat.com>
Date: Mon, 18 Nov 2024 09:25:09 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: dongml2@...natelecom.cn, menglong8.dong@...il.com
Cc: syzbot <syzbot+52fbd90f020788ec7709@...kaller.appspotmail.com>,
 davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com,
 horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] WARNING in sk_skb_reason_drop

On 11/16/24 19:32, syzbot wrote:
> HEAD commit:    a58f00ed24b8 net: sched: cls_api: improve the error messag..
> git tree:       net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=140a735f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=47cb6c16bf912470
> dashboard link: https://syzkaller.appspot.com/bug?extid=52fbd90f020788ec7709
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=132804c0580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f481a7980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d28dcea68102/disk-a58f00ed.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/8ec032ea06c6/vmlinux-a58f00ed.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/da9b8f80c783/bzImage-a58f00ed.xz
> 
> The issue was bisected to:
> 
> commit 82d9983ebeb871cb5abd27c12a950c14c68772e1
> Author: Menglong Dong <menglong8.dong@...il.com>
> Date:   Thu Nov 7 12:55:58 2024 +0000
> 
>     net: ip: make ip_route_input_noref() return drop reasons
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10ae41a7980000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=12ae41a7980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14ae41a7980000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+52fbd90f020788ec7709@...kaller.appspotmail.com
> Fixes: 82d9983ebeb8 ("net: ip: make ip_route_input_noref() return drop reasons")
> 
> netlink: 'syz-executor371': attribute type 4 has an invalid length.
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 5842 at net/core/skbuff.c:1219 __sk_skb_reason_drop net/core/skbuff.c:1216 [inline]
> WARNING: CPU: 0 PID: 5842 at net/core/skbuff.c:1219 sk_skb_reason_drop+0x87/0x380 net/core/skbuff.c:1241
> Modules linked in:
> CPU: 0 UID: 0 PID: 5842 Comm: syz-executor371 Not tainted 6.12.0-rc6-syzkaller-01362-ga58f00ed24b8 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
> RIP: 0010:__sk_skb_reason_drop net/core/skbuff.c:1216 [inline]
> RIP: 0010:sk_skb_reason_drop+0x87/0x380 net/core/skbuff.c:1241
> Code: 00 00 00 fc ff df 41 8d 9e 00 00 fc ff bf 01 00 fc ff 89 de e8 ea 9f 08 f8 81 fb 00 00 fc ff 77 3a 4c 89 e5 e8 9a 9b 08 f8 90 <0f> 0b 90 eb 5e bf 01 00 00 00 89 ee e8 c8 9f 08 f8 85 ed 0f 8e 49
> RSP: 0018:ffffc90003d57078 EFLAGS: 00010293
> RAX: ffffffff898c3ec6 RBX: 00000000fffbffea RCX: ffff8880347a5a00
> RDX: 0000000000000000 RSI: 00000000fffbffea RDI: 00000000fffc0001
> RBP: dffffc0000000000 R08: ffffffff898c3eb6 R09: 1ffff110023eb7d4
> R10: dffffc0000000000 R11: ffffed10023eb7d5 R12: dffffc0000000000
> R13: ffff888011f5bdc0 R14: 00000000ffffffea R15: 0000000000000000
> FS:  000055557d41e380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000056519d31d608 CR3: 000000007854e000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  kfree_skb_reason include/linux/skbuff.h:1263 [inline]
>  ip_rcv_finish_core+0xfde/0x1b50 net/ipv4/ip_input.c:424
>  ip_list_rcv_finish net/ipv4/ip_input.c:610 [inline]
>  ip_sublist_rcv+0x3b1/0xab0 net/ipv4/ip_input.c:636
>  ip_list_rcv+0x42b/0x480 net/ipv4/ip_input.c:670
>  __netif_receive_skb_list_ptype net/core/dev.c:5715 [inline]
>  __netif_receive_skb_list_core+0x94e/0x980 net/core/dev.c:5762
>  __netif_receive_skb_list net/core/dev.c:5814 [inline]
>  netif_receive_skb_list_internal+0xa51/0xe30 net/core/dev.c:5905
>  netif_receive_skb_list+0x55/0x4b0 net/core/dev.c:5957
>  xdp_recv_frames net/bpf/test_run.c:280 [inline]
>  xdp_test_run_batch net/bpf/test_run.c:361 [inline]
>  bpf_test_run_xdp_live+0x1b5e/0x21b0 net/bpf/test_run.c:390
>  bpf_prog_test_run_xdp+0x805/0x11e0 net/bpf/test_run.c:1318
>  bpf_prog_test_run+0x2e4/0x360 kernel/bpf/syscall.c:4266
>  __sys_bpf+0x48d/0x810 kernel/bpf/syscall.c:5671
>  __do_sys_bpf kernel/bpf/syscall.c:5760 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5758 [inline]
>  __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5758
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f18af25a8e9
> 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffee4090af8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f18af25a8e9
> RDX: 0000000000000048 RSI: 0000000020000600 RDI: 000000000000000a
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> 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.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report

@Menglong Dong: could you please have a look? The repro looks
deterministic, so it should be doable to pin-point the actual, bad
drop_reason and why/which function is triggering it. My wild guess is
that an ERRNO is type-casted to drop reason instead of being converted.

Cheers,

Paolo

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