linux-kernel - [syzbot ci] Re: slab: Introduce __SECOND_OBJEXT_FLAG for objext

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Message-ID: <68ee4be0.050a0220.ac43.0104.GAE@google.com>
Date: Tue, 14 Oct 2025 06:10:56 -0700
From: syzbot ci <syzbot+cid6b2cf8227adc21a@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, ast@...nel.org, cgroups@...r.kernel.org, 
	gehao@...inos.cn, hannes@...xchg.org, hao.ge@...ux.dev, harry.yoo@...cle.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...nel.org, 
	muchun.song@...ux.dev, roman.gushchin@...ux.dev, shakeel.butt@...ux.dev, 
	surenb@...gle.com, vbabka@...e.cz
Cc: syzbot@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: [syzbot ci] Re: slab: Introduce __SECOND_OBJEXT_FLAG for objext_flags

syzbot ci has tested the following series

[v1] slab: Introduce __SECOND_OBJEXT_FLAG for objext_flags
https://lore.kernel.org/all/20251014093124.300012-1-hao.ge@linux.dev
* [PATCH] slab: Introduce __SECOND_OBJEXT_FLAG for objext_flags

and found the following issue:
general protection fault in percpu_ref_get_many

Full report is available here:
https://ci.syzbot.org/series/6fd66120-211f-479f-b6a1-35f990da2dc2

***

general protection fault in percpu_ref_get_many

tree:      torvalds
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base:      0d97f2067c166eb495771fede9f7b73999c67f66
arch:      amd64
compiler:  Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config:    https://ci.syzbot.org/builds/74de5bb7-695b-4115-9a4b-ee7d7fd0cca2/config

Oops: general protection fault, probably for non-canonical address 0xdffffc00177780ff: 0000 [#1] SMP KASAN PTI
KASAN: probably user-memory-access in range [0x00000000bbbc07f8-0x00000000bbbc07ff]
CPU: 1 UID: 0 PID: 6155 Comm: syz-executor 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:percpu_ref_get_many+0x8d/0x140
Code: 01 48 c7 c7 80 70 78 8b be 65 03 00 00 48 c7 c2 c0 70 78 8b e8 64 2b 6f ff 49 bc 00 00 00 00 00 fc ff df 4c 89 f8 48 c1 e8 03 <42> 80 3c 20 00 74 08 4c 89 ff e8 c4 50 f7 ff 49 8b 07 a8 03 75 62
RSP: 0018:ffffc90004df7500 EFLAGS: 00010206
RAX: 00000000177780ff RBX: ffffffff822de139 RCX: 14bab840e71f4400
RDX: 0000000000000000 RSI: ffffffff8bc074c0 RDI: ffffffff8bc07480
RBP: 0000000000000088 R08: 0000000000000000 R09: ffffffff822de139
R10: dffffc0000000000 R11: fffffbfff1f3c1ef R12: dffffc0000000000
R13: ffff88823c63b5c0 R14: 0000000000000001 R15: 00000000bbbc07f8
FS:  0000555570ae6500(0000) GS:ffff8882a9d12000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555562d8c5c8 CR3: 0000000113444000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 refill_obj_stock+0x254/0x850
 __memcg_slab_free_hook+0x123/0x3b0
 kfree+0x3f7/0x6d0
 kobject_uevent_env+0x361/0x8c0
 netdev_queue_update_kobjects+0x346/0x6c0
 netdev_register_kobject+0x258/0x310
 register_netdevice+0x126c/0x1ae0
 __ip_tunnel_create+0x3e7/0x560
 ip_tunnel_init_net+0x2ba/0x800
 ops_init+0x35c/0x5c0
 setup_net+0xfe/0x320
 copy_net_ns+0x34e/0x4e0
 create_new_namespaces+0x3f3/0x720
 unshare_nsproxy_namespaces+0x11c/0x170
 ksys_unshare+0x4c8/0x8c0
 __x64_sys_unshare+0x38/0x50
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f85c81906c7
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 10 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe57c0ca58 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f85c81906c7
RDX: 00007f85c818eec9 RSI: 00007ffe57c0ca20 RDI: 0000000040000000
RBP: 00007ffe57c0cac0 R08: 00007f85c83a69d0 R09: 00007f85c83a69d0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe57c0cac0
R13: 00007ffe57c0cac8 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:percpu_ref_get_many+0x8d/0x140
Code: 01 48 c7 c7 80 70 78 8b be 65 03 00 00 48 c7 c2 c0 70 78 8b e8 64 2b 6f ff 49 bc 00 00 00 00 00 fc ff df 4c 89 f8 48 c1 e8 03 <42> 80 3c 20 00 74 08 4c 89 ff e8 c4 50 f7 ff 49 8b 07 a8 03 75 62
RSP: 0018:ffffc90004df7500 EFLAGS: 00010206
RAX: 00000000177780ff RBX: ffffffff822de139 RCX: 14bab840e71f4400
RDX: 0000000000000000 RSI: ffffffff8bc074c0 RDI: ffffffff8bc07480
RBP: 0000000000000088 R08: 0000000000000000 R09: ffffffff822de139
R10: dffffc0000000000 R11: fffffbfff1f3c1ef R12: dffffc0000000000
R13: ffff88823c63b5c0 R14: 0000000000000001 R15: 00000000bbbc07f8
FS:  0000555570ae6500(0000) GS:ffff8882a9d12000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555562d8c5c8 CR3: 0000000113444000 CR4: 00000000000006f0


***

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@...kaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@...glegroups.com.