Message-ID: <690dd2a8.a70a0220.22f260.003d.GAE@google.com>
Date: Fri, 07 Nov 2025 03:06:16 -0800
From: syzbot ci <syzbot+ci348771c1c9b7511f@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, atenart@...nel.org, davem@...emloft.net, 
	ebiederm@...ssion.com, edumazet@...gle.com, gregkh@...e.de, horms@...nel.org, 
	kuba@...nel.org, kuniyu@...gle.com, linux-kernel@...r.kernel.org, 
	make24@...as.ac.cn, netdev@...r.kernel.org, pabeni@...hat.com, 
	sdf@...ichev.me, stable@...r.kernel.org, yajun.deng@...ux.dev
Cc: syzbot@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: [syzbot ci] Re: net: Fix error handling in netdev_register_kobject

syzbot ci has tested the following series

[v1] net: Fix error handling in netdev_register_kobject
https://lore.kernel.org/all/20251107080117.15099-1-make24@iscas.ac.cn
* [PATCH] net: Fix error handling in netdev_register_kobject

and found the following issue:
KASAN: slab-use-after-free Read in netdev_run_todo

Full report is available here:
https://ci.syzbot.org/series/29bd058e-ea85-48e2-9bb9-ff9c0214f12e

***

KASAN: slab-use-after-free Read in netdev_run_todo

tree:      net-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base:      8a25a2e34157d882032112e4194ccdfb29c499e8
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/2f985280-f9ef-47c8-b4ec-80d44968222b/config

==================================================================
BUG: KASAN: slab-use-after-free in kobject_put+0x2ab/0x480
Read of size 1 at addr ffff888113992714 by task kworker/u8:0/12

CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:0 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
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 kobject_put+0x2ab/0x480
 netdev_run_todo+0xd2e/0xea0
 ops_undo_list+0x3e1/0x990
 cleanup_net+0x4d8/0x820
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 5810:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kvmalloc_node_noprof+0x5cd/0x910
 alloc_netdev_mqs+0xa6/0x11b0
 ip6gre_init_net+0xb5/0x3c0
 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

Freed by task 12:
 kasan_save_track+0x3e/0x80
 __kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5c/0x80
 kfree+0x19a/0x6d0
 device_release+0x9c/0x1c0
 kobject_put+0x22b/0x480
 netdev_run_todo+0xd0c/0xea0
 ops_undo_list+0x3e1/0x990
 cleanup_net+0x4d8/0x820
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30

The buggy address belongs to the object at ffff888113992000
 which belongs to the cache kmalloc-cg-4k of size 4096
The buggy address is located 1812 bytes inside of
 freed 4096-byte region [ffff888113992000, ffff888113993000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x113990
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000040 ffff88810004b500 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 017ff00000000040 ffff88810004b500 dead000000000122 0000000000000000
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 017ff00000000003 ffffea00044e6401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5810, tgid 5810 (syz-executor), ts 65154411256, free_ts 60842795356
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x2365/0x2440
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x96/0x350
 ___slab_alloc+0xe94/0x18a0
 __slab_alloc+0x65/0x100
 __kmalloc_noprof+0x471/0x7f0
 __register_sysctl_table+0x72/0x1340
 __addrconf_sysctl_register+0x328/0x4c0
 addrconf_sysctl_register+0x168/0x1c0
 ipv6_add_dev+0xd46/0x1370
 addrconf_notify+0x794/0x1010
 notifier_call_chain+0x1b6/0x3e0
 register_netdevice+0x1608/0x1ae0
 register_netdev+0x40/0x60
page last free pid 15 tgid 15 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __folio_put+0x21b/0x2c0
 skb_release_data+0x49a/0x7c0
 napi_consume_skb+0x158/0x1e0
 skb_defer_free_flush+0x18f/0x250
 net_rx_action+0x804/0xe50
 handle_softirqs+0x286/0x870
 run_ksoftirqd+0x9b/0x100
 smpboot_thread_fn+0x542/0xa60
 kthread+0x711/0x8a0
 ret_from_fork+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30

Memory state around the buggy address:
 ffff888113992600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888113992680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888113992700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888113992780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888113992800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


***

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.

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