[moderation/CI] Re: xfrm: fix IPv6 atomic fragment policy handling

[moderation/CI] Re: xfrm: fix IPv6 atomic fragment policy handling

[syzbot ci]

syzbot ci has tested the following series

[v3] xfrm: fix IPv6 atomic fragment policy handling
https://lore.kernel.org/all/20261106202910.723098-2-Jeremy.Jean@oss.cyber.gouv.fr
* [PATCH net v3 1/2] xfrm: fix IPv6 first-fragment protocol decode
* [PATCH net v3 2/2] xfrm: fix selector matching for IPv6 atomic fragments

and found the following issue:
WARNING in __xfrm_decode_session

Full report is available here:
https://ci.syzbot.org/series/9d92ff08-0b82-4440-b345-9628353f5181

***

WARNING in __xfrm_decode_session

tree:      net
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
base:      2d2200551ccc3b9e444aecb59c4b53287e169266
arch:      amd64
compiler:  Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/fe2ead38-2a3d-497a-9bae-e5da0ee59933/config
AI triage: https://ci.syzbot.org/findings/072b992e-75d5-4bd7-b9e1-5247e374123e/triage_trajectory

------------[ cut here ]------------
len > ((int)(~0U >> 1))
WARNING: ./include/linux/skbuff.h:2856 at __xfrm_decode_session+0xafb/0xed0, CPU#0: syz.0.121/6184
Modules linked in:
CPU: 0 UID: 0 PID: 6184 Comm: syz.0.121 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:__xfrm_decode_session+0xafb/0xed0
Code: bf e0 00 00 00 4d 03 3e 4c 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 11 03 00 00 45 8b 37 e9 33 fd ff ff e8 c6 c7 30 f7 90 <0f> 0b 90 e9 8c f7 ff ff 44 89 ef 8b 5c 24 20 89 de e8 bf c9 30 f7
RSP: 0018:ffffc9000e926b60 EFLAGS: 00010283
RAX: ffffffff8a9849aa RBX: 1ffff92001d24d74 RCX: 0000000000080000
RDX: ffffc90006ec1000 RSI: 0000000000000c7f RDI: 0000000000000c80
RBP: ffffc9000e926c90 R08: ffff88816dd8bc00 R09: 0000000000000002
R10: 000000000000000a R11: 0000000000000002 R12: ffffc9000e926bc0
R13: 00000000fffffff8 R14: ffff888105f226d8 R15: dffffc0000000000
FS:  00007fc136da96c0(0000) GS:ffff88818be0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002cc0 CR3: 000000017256e000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 icmpv6_route_lookup+0x44a/0x610
 icmp6_send+0x114c/0x1b50
 icmpv6_param_prob_reason+0x32/0x50
 ipv6_frag_rcv+0x927/0x2b40
 ip6_protocol_deliver_rcu+0xe8c/0x1680
 ip6_input_finish+0x191/0x370
 NF_HOOK+0x336/0x3c0
 ip6_input+0x16a/0x270
 NF_HOOK+0x336/0x3c0
 netif_receive_skb+0x278/0xbf0
 tun_rx_batched+0x1de/0x790
 tun_get_user+0x2b78/0x4470
 tun_chr_write_iter+0x113/0x200
 vfs_write+0x612/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc135f6974e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007fc136da8fb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc136da96c0 RCX: 00007fc135f6974e
RDX: 000000000000004a RSI: 0000200000000700 RDI: 00000000000000c8
RBP: 00007fc136037f6d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc136226038 R14: 00007fc136225fa0 R15: 00007ffcfeaad798
 </TASK>


***

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.

To test a fix for this bug, please reply with `#syz test`
(on a separate line) and attach the patch to the email.

Notes:
- The patch will be applied on top of the tested series (as an
  incremental fix).
- To test a new version of the whole series, please send it directly
  to syzbot@lists.linux.dev.
- Arguments like custom git repos and branches are not supported.

The email will later be sent to:
[davem@davemloft.net dsahern@kernel.org herbert@gondor.apana.org.au idosch@nvidia.com jeremy.jean@oss.cyber.gouv.fr linux-kernel@vger.kernel.org netdev@vger.kernel.org stable@vger.kernel.org steffen.klassert@secunet.com]

If the report looks fine to you, reply with:
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If the report is a false positive, reply with
#syz invalid

Re: [moderation/CI] Re: xfrm: fix IPv6 atomic fragment policy handling

[Aleksandr Nogikh]

#syz upstream


On Tue, Nov 10, 2026 at 8:02 AM syzbot ci
<syzbot+ci45a8a6066bea8b92@syzkaller.appspotmail.com> wrote:
>
> syzbot ci has tested the following series
>
> [v3] xfrm: fix IPv6 atomic fragment policy handling
> https://lore.kernel.org/all/20261106202910.723098-2-Jeremy.Jean@oss.cyber.gouv.fr
> * [PATCH net v3 1/2] xfrm: fix IPv6 first-fragment protocol decode
> * [PATCH net v3 2/2] xfrm: fix selector matching for IPv6 atomic fragments
>
> and found the following issue:
> WARNING in __xfrm_decode_session
>
> Full report is available here:
> https://ci.syzbot.org/series/9d92ff08-0b82-4440-b345-9628353f5181
>
> ***
>
> WARNING in __xfrm_decode_session
>
> tree:      net
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
> base:      2d2200551ccc3b9e444aecb59c4b53287e169266
> arch:      amd64
> compiler:  Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
> config:    https://ci.syzbot.org/builds/fe2ead38-2a3d-497a-9bae-e5da0ee59933/config
> AI triage: https://ci.syzbot.org/findings/072b992e-75d5-4bd7-b9e1-5247e374123e/triage_trajectory
>
> ------------[ cut here ]------------
> len > ((int)(~0U >> 1))
> WARNING: ./include/linux/skbuff.h:2856 at __xfrm_decode_session+0xafb/0xed0, CPU#0: syz.0.121/6184
> Modules linked in:
> CPU: 0 UID: 0 PID: 6184 Comm: syz.0.121 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:__xfrm_decode_session+0xafb/0xed0
> Code: bf e0 00 00 00 4d 03 3e 4c 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 11 03 00 00 45 8b 37 e9 33 fd ff ff e8 c6 c7 30 f7 90 <0f> 0b 90 e9 8c f7 ff ff 44 89 ef 8b 5c 24 20 89 de e8 bf c9 30 f7
> RSP: 0018:ffffc9000e926b60 EFLAGS: 00010283
> RAX: ffffffff8a9849aa RBX: 1ffff92001d24d74 RCX: 0000000000080000
> RDX: ffffc90006ec1000 RSI: 0000000000000c7f RDI: 0000000000000c80
> RBP: ffffc9000e926c90 R08: ffff88816dd8bc00 R09: 0000000000000002
> R10: 000000000000000a R11: 0000000000000002 R12: ffffc9000e926bc0
> R13: 00000000fffffff8 R14: ffff888105f226d8 R15: dffffc0000000000
> FS:  00007fc136da96c0(0000) GS:ffff88818be0d000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000002cc0 CR3: 000000017256e000 CR4: 00000000000006f0
> Call Trace:
>  <TASK>
>  icmpv6_route_lookup+0x44a/0x610
>  icmp6_send+0x114c/0x1b50
>  icmpv6_param_prob_reason+0x32/0x50
>  ipv6_frag_rcv+0x927/0x2b40
>  ip6_protocol_deliver_rcu+0xe8c/0x1680
>  ip6_input_finish+0x191/0x370
>  NF_HOOK+0x336/0x3c0
>  ip6_input+0x16a/0x270
>  NF_HOOK+0x336/0x3c0
>  netif_receive_skb+0x278/0xbf0
>  tun_rx_batched+0x1de/0x790
>  tun_get_user+0x2b78/0x4470
>  tun_chr_write_iter+0x113/0x200
>  vfs_write+0x612/0xba0
>  ksys_write+0x150/0x270
>  do_syscall_64+0x166/0x520
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc135f6974e
> Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
> RSP: 002b:00007fc136da8fb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007fc136da96c0 RCX: 00007fc135f6974e
> RDX: 000000000000004a RSI: 0000200000000700 RDI: 00000000000000c8
> RBP: 00007fc136037f6d R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fc136226038 R14: 00007fc136225fa0 R15: 00007ffcfeaad798
>  </TASK>
>
>
> ***
>
> 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.
>
> To test a fix for this bug, please reply with `#syz test`
> (on a separate line) and attach the patch to the email.
>
> Notes:
> - The patch will be applied on top of the tested series (as an
>   incremental fix).
> - To test a new version of the whole series, please send it directly
>   to syzbot@lists.linux.dev.
> - Arguments like custom git repos and branches are not supported.
>
> The email will later be sent to:
> [davem@davemloft.net dsahern@kernel.org herbert@gondor.apana.org.au idosch@nvidia.com jeremy.jean@oss.cyber.gouv.fr linux-kernel@vger.kernel.org netdev@vger.kernel.org stable@vger.kernel.org steffen.klassert@secunet.com]
>
> If the report looks fine to you, reply with:
> #syz upstream
>
> If the report is a false positive, reply with
> #syz invalid
>
> --
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