Subject: [syzbot ci] Re: net: nsh: limit recursive GSO redispatch

From: syzbot ci <[email-masked]>
Date: Sun, 10 May 2026 04:45:18 -0700

syzbot ci has tested the following series

[v2] net: nsh: limit recursive GSO redispatch
https://lore.kernel.org/all/67e[email-masked]
* [PATCH net v2 1/1] net: nsh: limit recursive GSO redispatch

and found the following issue:
BUG: using __this_cpu_read() in preemptible code in nsh_gso_segment

Full report is available here:
https://ci.syzbot.org/series/cb23e640-2f7a-42e1-8bad-7249684b1cd5

***

BUG: using __this_cpu_read() in preemptible code in nsh_gso_segment

tree:      net
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
base:      496c0c4c53bbe1bad97e82cd12103df61a6e459d
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/a7e3d1e1-97c4-4876-99c8-658c4cef49c5/config
syz repro: https://ci.syzbot.org/findings/62ca20c2-7c78-4820-b695-f63b15eaf738/syz_repro

BUG: using __this_cpu_read() in preemptible [00000000] code: syz.1.18/5860
caller is dev_xmit_recursion include/linux/netdevice.h:3625 [inline]
caller is nsh_gso_segment+0x535/0xed0 net/nsh/nsh.c:110
CPU: 0 UID: 0 PID: 5860 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
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 check_preemption_disabled+0xd3/0xe0 lib/smp_processor_id.c:47
 dev_xmit_recursion include/linux/netdevice.h:3625 [inline]
 nsh_gso_segment+0x535/0xed0 net/nsh/nsh.c:110
 skb_mac_gso_segment+0x31c/0x690 net/core/gso.c:53
 __skb_gso_segment+0x376/0x540 net/core/gso.c:124
 skb_gso_segment include/net/gso.h:83 [inline]
 validate_xmit_skb+0xa21/0x14a0 net/core/dev.c:4039
 validate_xmit_skb_list net/core/dev.c:4089 [inline]
 __dev_direct_xmit+0x1b4/0x750 net/core/dev.c:4922
 dev_direct_xmit include/linux/netdevice.h:3431 [inline]
 packet_xmit+0x1b4/0x320 net/packet/af_packet.c:285
 packet_snd net/packet/af_packet.c:3082 [inline]
 packet_sendmsg+0x3c81/0x4fb0 net/packet/af_packet.c:3114
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x672/0x710 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2268
 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: 0033:0x7fcd6a99cdd9
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:00007fcd6b903028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fcd6ac15fa0 RCX: 00007fcd6a99cdd9
RDX: 00000000000100a6 RSI: 0000200000000180 RDI: 0000000000000005
RBP: 00007fcd6aa32d69 R08: 0000200000000140 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcd6ac16038 R14: 00007fcd6ac15fa0 R15: 00007fff57a83608
 </TASK>
BUG: using __this_cpu_add() in preemptible [00000000] code: syz.1.18/5860
caller is dev_xmit_recursion_inc include/linux/netdevice.h:3631 [inline]
caller is nsh_gso_segment+0x57d/0xed0 net/nsh/nsh.c:113
CPU: 0 UID: 0 PID: 5860 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
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 check_preemption_disabled+0xd3/0xe0 lib/smp_processor_id.c:47
 dev_xmit_recursion_inc include/linux/netdevice.h:3631 [inline]
 nsh_gso_segment+0x57d/0xed0 net/nsh/nsh.c:113
 skb_mac_gso_segment+0x31c/0x690 net/core/gso.c:53
 __skb_gso_segment+0x376/0x540 net/core/gso.c:124
 skb_gso_segment include/net/gso.h:83 [inline]
 validate_xmit_skb+0xa21/0x14a0 net/core/dev.c:4039
 validate_xmit_skb_list net/core/dev.c:4089 [inline]
 __dev_direct_xmit+0x1b4/0x750 net/core/dev.c:4922
 dev_direct_xmit include/linux/netdevice.h:3431 [inline]
 packet_xmit+0x1b4/0x320 net/packet/af_packet.c:285
 packet_snd net/packet/af_packet.c:3082 [inline]
 packet_sendmsg+0x3c81/0x4fb0 net/packet/af_packet.c:3114
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x672/0x710 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2268
 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: 0033:0x7fcd6a99cdd9
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:00007fcd6b903028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fcd6ac15fa0 RCX: 00007fcd6a99cdd9
RDX: 00000000000100a6 RSI: 0000200000000180 RDI: 0000000000000005
RBP: 00007fcd6aa32d69 R08: 0000200000000140 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcd6ac16038 R14: 00007fcd6ac15fa0 R15: 00007fff57a83608
 </TASK>
BUG: using __this_cpu_add() in preemptible [00000000] code: syz.1.18/5860
caller is dev_xmit_recursion_dec include/linux/netdevice.h:3636 [inline]
caller is nsh_gso_segment+0x59f/0xed0 net/nsh/nsh.c:115
CPU: 0 UID: 0 PID: 5860 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
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 check_preemption_disabled+0xd3/0xe0 lib/smp_processor_id.c:47
 dev_xmit_recursion_dec include/linux/netdevice.h:3636 [inline]
 nsh_gso_segment+0x59f/0xed0 net/nsh/nsh.c:115
 skb_mac_gso_segment+0x31c/0x690 net/core/gso.c:53
 __skb_gso_segment+0x376/0x540 net/core/gso.c:124
 skb_gso_segment include/net/gso.h:83 [inline]
 validate_xmit_skb+0xa21/0x14a0 net/core/dev.c:4039
 validate_xmit_skb_list net/core/dev.c:4089 [inline]
 __dev_direct_xmit+0x1b4/0x750 net/core/dev.c:4922
 dev_direct_xmit include/linux/netdevice.h:3431 [inline]
 packet_xmit+0x1b4/0x320 net/packet/af_packet.c:285
 packet_snd net/packet/af_packet.c:3082 [inline]
 packet_sendmsg+0x3c81/0x4fb0 net/packet/af_packet.c:3114
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 __sys_sendto+0x672/0x710 net/socket.c:2265
 __do_sys_sendto net/socket.c:2272 [inline]
 __se_sys_sendto net/socket.c:2268 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2268
 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: 0033:0x7fcd6a99cdd9
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:00007fcd6b903028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fcd6ac15fa0 RCX: 00007fcd6a99cdd9
RDX: 00000000000100a6 RSI: 0000200000000180 RDI: 0000000000000005
RBP: 00007fcd6aa32d69 R08: 0000200000000140 R09: 0000000000000014
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcd6ac16038 R14: 00007fcd6ac15fa0 R15: 00007fff57a83608
 </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: [email-masked]

---
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