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[PATCH] net: Fix error handling in netdev_register_kobject

Ma Ke posted 1 patch 1 month, 1 week ago 
net/core/net-sysfs.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
[PATCH] net: Fix error handling in netdev_register_kobject
Posted by Ma Ke 1 month, 1 week ago 
After calling device_initialize(), the reference count of the device
is set to 1. If device_add() fails or register_queue_kobjects() fails,
the function returns without calling put_device() to release the
initial reference, causing a memory leak of the device structure.
Similarly, in netdev_unregister_kobject(), after calling device_del(),
there is no call to put_device() to release the initial reference,
leading to a memory leak. Add put_device() in the error paths of
netdev_register_kobject() and after device_del() in
netdev_unregister_kobject() to properly release the device references.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: a1b3f594dc5f ("net: Expose all network devices in a namespaces in sysfs")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 net/core/net-sysfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index ca878525ad7c..d3895f26a0c8 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -2327,6 +2327,7 @@ void netdev_unregister_kobject(struct net_device *ndev)
 	pm_runtime_set_memalloc_noio(dev, false);
 
 	device_del(dev);
+	put_device(dev);
 }
 
 /* Create sysfs entries for network device. */
@@ -2357,7 +2358,7 @@ int netdev_register_kobject(struct net_device *ndev)
 
 	error = device_add(dev);
 	if (error)
-		return error;
+		goto out_put_device;
 
 	error = register_queue_kobjects(ndev);
 	if (error) {
@@ -2367,6 +2368,10 @@ int netdev_register_kobject(struct net_device *ndev)
 
 	pm_runtime_set_memalloc_noio(dev, true);
 
+	return 0;
+
+out_put_device:
+	put_device(dev);
 	return error;
 }
 
-- 
2.17.1
Re: [PATCH] net: Fix error handling in netdev_register_kobject
Posted by kernel test robot 1 month, 1 week ago 
Hello,

kernel test robot noticed "BUG_kmalloc-#k:Object_corrupt" on:

commit: 6e383382971f4573e29f0e85c6e5667c8f5f46d6 ("[PATCH] net: Fix error handling in netdev_register_kobject")
url: https://github.com/intel-lab-lkp/linux/commits/Ma-Ke/net-Fix-error-handling-in-netdev_register_kobject/20251107-160348
base: https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git 6fc33710cd6c55397e606eeb544bdf56ee87aae5
patch link: https://lore.kernel.org/all/20251107080117.15099-1-make24@iscas.ac.cn/
patch subject: [PATCH] net: Fix error handling in netdev_register_kobject

in testcase: boot

config: i386-randconfig-014-20251110
compiler: gcc-14
test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G

(please refer to attached dmesg/kmsg for entire log/backtrace)



If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <oliver.sang@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202511121347.b3f6c2a3-lkp@intel.com


[  OK  ] Started /etc/rc.local Compatibility.
LKP: ttyS0: 250: skip deploy intel ucode as no ucode is specified
[   15.199659] rc.local[250]: LKP: stdout: 250: skip deploy intel ucode as no ucode is specified
[   15.508990][    T1] [Poison overwritten] 0xf5e12370-0xf5e12370 @offset=9072. First byte 0x6a instead of 0x6b
[   15.511968][    T1] =============================================================================
[   15.514232][    T1] BUG kmalloc-2k (Tainted: G S                 ): Object corrupt
[   15.516308][    T1] -----------------------------------------------------------------------------
[   15.516308][    T1]
[   15.519187][    T1] Allocated in alloc_netdev_mqs+0x7d/0x470 age=517 cpu=1 pid=191
[   15.521218][    T1]  __slab_alloc+0x53/0x80
[   15.522561][    T1]  __kvmalloc_node_noprof (kbuild/src/consumer/mm/slub.c:4846 kbuild/src/consumer/mm/slub.c:5268 kbuild/src/consumer/mm/slub.c:5641 kbuild/src/consumer/mm/slub.c:7100)


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20251112/202511121347.b3f6c2a3-lkp@intel.com



-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH] net: Fix error handling in netdev_register_kobject
Posted by Eric Dumazet 1 month, 1 week ago 
On Fri, Nov 7, 2025 at 12:01 AM Ma Ke <make24@iscas.ac.cn> wrote:
>
> After calling device_initialize(), the reference count of the device
> is set to 1. If device_add() fails or register_queue_kobjects() fails,
> the function returns without calling put_device() to release the
> initial reference, causing a memory leak of the device structure.
> Similarly, in netdev_unregister_kobject(), after calling device_del(),
> there is no call to put_device() to release the initial reference,
> leading to a memory leak. Add put_device() in the error paths of
> netdev_register_kobject() and after device_del() in
> netdev_unregister_kobject() to properly release the device references.
>
> Found by code review.
>
> Cc: stable@vger.kernel.org
> Fixes: a1b3f594dc5f ("net: Expose all network devices in a namespaces in sysfs")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
>  net/core/net-sysfs.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index ca878525ad7c..d3895f26a0c8 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -2327,6 +2327,7 @@ void netdev_unregister_kobject(struct net_device *ndev)
>         pm_runtime_set_memalloc_noio(dev, false);
>
>         device_del(dev);
> +       put_device(dev);

Please take a look at free_netdev()

>  }
>
>  /* Create sysfs entries for network device. */
> @@ -2357,7 +2358,7 @@ int netdev_register_kobject(struct net_device *ndev)
>
>         error = device_add(dev);
>         if (error)
> -               return error;
> +               goto out_put_device;
>
>         error = register_queue_kobjects(ndev);
>         if (error) {
> @@ -2367,6 +2368,10 @@ int netdev_register_kobject(struct net_device *ndev)
>
>         pm_runtime_set_memalloc_noio(dev, true);
>
> +       return 0;
> +
> +out_put_device:
> +       put_device(dev);
>         return error;

This seems bogus.

Was your report based on AI or some tooling ?

You would think that syzbot would have found an issue a long time ago...
[syzbot ci] Re: net: Fix error handling in netdev_register_kobject
Posted by syzbot ci 1 month, 1 week ago 
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@syzkaller.appspotmail.com

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

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