KASAN: slab-use-after-free Write in arp_create

Status: fixed on 2026/05/06 16:40
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+58b44a770a1585795351@syzkaller.appspotmail.com
Fix commit: c92510f5e3f8 arp: do not assume dev_hard_header() does not change skb->head
First crash: 198d, last: 128d
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
8aa58720 repro ❓ KASAN: slab-use-after-free Write in arp_create 2026/03/07 07:17 2026/03/07 07:17 2026/03/07 07:33 31e9c887 

			
				
	

	
	



			

		

	

	
	

		

			▶
			▼
			Discussions (3)
		

		

			
			
			



	
	

		Title
		Replies (including bot)
		Last reply
	

	
	
	
		

			[PATCH 6.12] arp: do not assume dev_hard_header() does not change skb->head
			1 (1)
			2026/01/12 18:50
		

	
		

			[PATCH net] arp: do not assume dev_hard_header() does not change skb->head
			2 (2)
			2026/01/08 17:10
		

	
		

			[syzbot] [net?] KASAN: slab-use-after-free Write in arp_create
			0 (1)
			2026/01/07 21:00
		

	
	




			
			
		

	

	
	

		

			▶
			▼
			Similar bugs (7)
		

		

			




	
	

		
			Kernel
		
		Title
		
			Rank
			
🛈

		
		Repro
		Cause bisect
		Fix bisect
		Count
		Last
		Reported
		
		
		
			Patched
		
		
			Status
		
		
	

	
	
	
		

			upstream
			
				general protection fault in arp_create (2)
					net
			
			2
			
			
			
			1
			603d
			
				
					603d
				
			
			
			
			
				0/29
			
			
				
					
						closed as invalid on 2025/01/02 16:12
					
				
			
			
		

	
		

			linux-5.15
			
				general protection fault in arp_create
			
			2
			
			
			
			1
			675d
			
				
					675d
				
			
			
			
			
				0/3
			
			
				
					
						auto-obsoleted due to no activity on 2024/12/27 05:27
					
				
			
			
		

	
		

			linux-6.1
			
				general protection fault in arp_create
			
			2
			
			
			
			1
			578d
			
				
					578d
				
			
			
			
			
				0/3
			
			
				
					
						auto-obsoleted due to no activity on 2025/04/02 22:52
					
				
			
			
		

	
		

			upstream
			
				general protection fault in arp_create
					net
			
			8
			
			
			
			3
			735d
			
				
					823d
				
			
			
			
			
				0/29
			
			
				
					
						auto-obsoleted due to no activity on 2024/10/17 18:02
					
				
			
			
		

	
		

			linux-6.1
			
				BUG: unable to handle kernel paging request in arp_create
			
			8
			
			
			
			1
			129d
			
				
					129d
				
			
			
			
			
				0/3
			
			
				
					
						auto-obsoleted due to no activity on 2026/06/25 09:46
					
				
			
			
		

	
		

			upstream
			
				general protection fault in arp_create (4)
					prio:high
					net
			
			2
			
			
			
			2
			70d
			
				
					68d
				
			
			
			
			
				29/29
			
			
				
					
						fixed on 2026/07/15 08:27
					
				
			
			
		

	
		

			upstream
			
				general protection fault in arp_create (3)
					net
			
			2
			
			
			
			4
			496d
			
				
					529d
				
			
			
			
			
				0/29
			
			
				
					
						auto-obsoleted due to no activity on 2025/06/23 14:12
					
				
			
			
		

	
	





			
			
			
			
		

	

	

	
	
Sample crash report:

	
sit0: left promiscuous mode
ip6gre0: left promiscuous mode
==================================================================
BUG: KASAN: slab-use-after-free in arp_create+0x859/0x990 net/ipv4/arp.c:-1
Write of size 2 at addr ffff888031c51d50 by task syz.3.2633/16059

CPU: 0 UID: 0 PID: 16059 Comm: syz.3.2633 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 arp_create+0x859/0x990 net/ipv4/arp.c:-1
 arp_send_dst net/ipv4/arp.c:314 [inline]
 arp_send+0xa5/0x190 net/ipv4/arp.c:328
 inetdev_send_gratuitous_arp net/ipv4/devinet.c:1571 [inline]
 inetdev_event+0x1156/0x15b0 net/ipv4/devinet.c:1638
 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
 call_netdevice_notifiers net/core/dev.c:2281 [inline]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9803
 do_setlink+0xc55/0x41c0 net/core/rtnetlink.c:3158
 rtnl_group_changelink net/core/rtnetlink.c:3790 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3944 [inline]
 rtnl_newlink+0x14b0/0x1c90 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 ____sys_sendmsg+0x505/0x820 net/socket.c:2592
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f50a2d8f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f50a3c64038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f50a2fe6180 RCX: 00007f50a2d8f749
RDX: 0000000000000000 RSI: 0000200000000140 RDI: 000000000000000d
RBP: 00007f50a2e13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f50a2fe6218 R14: 00007f50a2fe6180 R15: 00007ffe4aa758d8
 </TASK>

Allocated by task 16059:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_node_noprof+0x43c/0x720 mm/slub.c:5315
 kmalloc_reserve+0xbd/0x290 net/core/skbuff.c:586
 __alloc_skb+0x204/0x3a0 net/core/skbuff.c:690
 alloc_skb include/linux/skbuff.h:1383 [inline]
 arp_create+0x189/0x990 net/ipv4/arp.c:561
 arp_send_dst net/ipv4/arp.c:314 [inline]
 arp_send+0xa5/0x190 net/ipv4/arp.c:328
 inetdev_send_gratuitous_arp net/ipv4/devinet.c:1571 [inline]
 inetdev_event+0x1156/0x15b0 net/ipv4/devinet.c:1638
 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
 call_netdevice_notifiers net/core/dev.c:2281 [inline]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9803
 do_setlink+0xc55/0x41c0 net/core/rtnetlink.c:3158
 rtnl_group_changelink net/core/rtnetlink.c:3790 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3944 [inline]
 rtnl_newlink+0x14b0/0x1c90 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 ____sys_sendmsg+0x505/0x820 net/socket.c:2592
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 16059:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6670 [inline]
 kmem_cache_free+0x197/0x620 mm/slub.c:6781
 pskb_expand_head+0x39e/0x1160 net/core/skbuff.c:2314
 ip6gre_header+0x13c/0x820 net/ipv6/ip6_gre.c:1376
 dev_hard_header include/linux/netdevice.h:3436 [inline]
 arp_create+0x3fd/0x990 net/ipv4/arp.c:578
 arp_send_dst net/ipv4/arp.c:314 [inline]
 arp_send+0xa5/0x190 net/ipv4/arp.c:328
 inetdev_send_gratuitous_arp net/ipv4/devinet.c:1571 [inline]
 inetdev_event+0x1156/0x15b0 net/ipv4/devinet.c:1638
 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
 call_netdevice_notifiers net/core/dev.c:2281 [inline]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9803
 do_setlink+0xc55/0x41c0 net/core/rtnetlink.c:3158
 rtnl_group_changelink net/core/rtnetlink.c:3790 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3944 [inline]
 rtnl_newlink+0x14b0/0x1c90 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 ____sys_sendmsg+0x505/0x820 net/socket.c:2592
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888031c51d40
 which belongs to the cache skbuff_small_head of size 704
The buggy address is located 16 bytes inside of
 freed 704-byte region [ffff888031c51d40, ffff888031c52000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x31c50
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801d6e1c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080130013 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801d6e1c80 dead000000000122 0000000000000000
head: 0000000000000000 0000000080130013 00000000f5000000 0000000000000000
head: 00fff00000000002 ffffea0000c71401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 16059, tgid 16050 (syz.3.2633), ts 579733121729, free_ts 429869578042
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0x24e0/0x2580 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xe53/0x1820 mm/slub.c:4656
 __slab_alloc+0x65/0x100 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 kmem_cache_alloc_node_noprof+0x4ce/0x720 mm/slub.c:5315
 kmalloc_reserve+0xbd/0x290 net/core/skbuff.c:586
 __alloc_skb+0x204/0x3a0 net/core/skbuff.c:690
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 inet_ifmcaddr_notify+0x7e/0x150 net/ipv4/igmp.c:1481
 ____ip_mc_inc_group+0x9a8/0xdd0 net/ipv4/igmp.c:1564
 __ip_mc_inc_group net/ipv4/igmp.c:1573 [inline]
 ip_mc_inc_group net/ipv4/igmp.c:1579 [inline]
 ip_mc_up+0x115/0x2e0 net/ipv4/igmp.c:1880
 inetdev_event+0xf93/0x15b0 net/ipv4/devinet.c:1630
 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
 call_netdevice_notifiers net/core/dev.c:2281 [inline]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
page last free pid 5186 tgid 5186 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2943
 __slab_free+0x2ce/0x320 mm/slub.c:6004
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 __do_kmalloc_node mm/slub.c:5656 [inline]
 __kmalloc_node_track_caller_noprof+0x526/0x820 mm/slub.c:5764
 kmalloc_reserve+0x136/0x290 net/core/skbuff.c:608
 __alloc_skb+0x204/0x3a0 net/core/skbuff.c:690
 alloc_skb include/linux/skbuff.h:1383 [inline]
 alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6712
 sock_alloc_send_pskb+0x84d/0x980 net/core/sock.c:2995
 unix_dgram_sendmsg+0x454/0x1840 net/unix/af_unix.c:2130
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 __sys_sendto+0x3bd/0x520 net/socket.c:2206
 __do_sys_sendto net/socket.c:2213 [inline]
 __se_sys_sendto net/socket.c:2209 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2209
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888031c51c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888031c51c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888031c51d00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                                 ^
 ffff888031c51d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888031c51e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================



	

	



	Crashes (2):
		
		

			Time
			Kernel
			Commit
			Syzkaller
			Config
			Log
			Report
			Syz repro
			C repro
			VM info
			Assets (help?)
			Manager
			Title
		

		
		
		
		

			2026/01/07 15:02
			net-next
			8e7148b56023
			d6526ea3
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
				[vmlinux]
			
				[kernel image]
			
			ci-upstream-net-kasan-gce
			KASAN: slab-use-after-free Write in arp_create
		

		
		

			2026/03/18 13:12
			upstream
			a989fde763f4
			0199f9a1
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
				[vmlinux]
			
				[kernel image]
			
			ci-upstream-kasan-gce-root
			general protection fault in arp_create
		

		
		


* Struck through repros no longer work on HEAD.