KASAN: stack-out-of-bounds Write in dev_map_redirect_multi

Status: fixed on 2026/05/06 16:40
Subsystems: bpf net
[Documentation on labels]
Reported-by: syzbot+10cc7f13760b31bd2e61@syzkaller.appspotmail.com
Fix commit: b7bf516c3ecd bpf: Fix stack-out-of-bounds write in devmap
First crash: 178d, last: 162d
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
e14aee67 repro ❓ KASAN: stack-out-of-bounds Write in dev_map_redirect_multi 2026/03/10 13:37 2026/03/10 23:49 2026/03/11 01:22 86914af9 

			
				
	

	
	



			

		

	

	
	

		

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			Discussions (5)
		

		

			
			
			



	
	

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			[PATCH v4 bpf] bpf: devmap: fix stack-out-of-bounds write in get_upper_ifindexes()
			2 (2)
			2026/02/26 19:30
		

	
		

			[PATCH v3 bpf] bpf: devmap: fix stack-out-of-bounds write in get_upper_ifindexes()
			3 (3)
			2026/02/24 10:58
		

	
		

			[PATCH v2 bpf] bpf: devmap: fix stack-out-of-bounds write in get_upper_ifindexes()
			3 (3)
			2026/02/23 13:32
		

	
		

			[PATCH v1 bpf] bpf: devmap: fix stack-out-of-bounds write in get_upper_ifindexes()
			2 (2)
			2026/02/20 02:44
		

	
		

			[syzbot] [bpf?] [net?] KASAN: stack-out-of-bounds Write in dev_map_redirect_multi
			0 (1)
			2026/02/11 09:33
		

	
	




			
			
		

	

	

	
	
Sample crash report:

	
==================================================================
BUG: KASAN: stack-out-of-bounds in get_upper_ifindexes kernel/bpf/devmap.c:601 [inline]
BUG: KASAN: stack-out-of-bounds in dev_map_redirect_multi+0x1bb/0xa00 kernel/bpf/devmap.c:736
Write of size 4 at addr ffffc900039f7164 by task syz.1.4880/24782

CPU: 1 UID: 0 PID: 24782 Comm: syz.1.4880 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 get_upper_ifindexes kernel/bpf/devmap.c:601 [inline]
 dev_map_redirect_multi+0x1bb/0xa00 kernel/bpf/devmap.c:736
 xdp_do_generic_redirect_map net/core/filter.c:4556 [inline]
 xdp_do_generic_redirect+0x669/0x820 net/core/filter.c:4619
 do_xdp_generic+0xcf7/0x12e0 net/core/dev.c:5617
 __netif_receive_skb_core+0x10e5/0x31a0 net/core/dev.c:5966
 __netif_receive_skb_one_core net/core/dev.c:6154 [inline]
 __netif_receive_skb net/core/dev.c:6269 [inline]
 netif_receive_skb_internal net/core/dev.c:6355 [inline]
 netif_receive_skb+0x1fe/0xc50 net/core/dev.c:6414
 tun_rx_batched+0x1de/0x790 drivers/net/tun.c:1485
 tun_get_user+0x2a78/0x3dd0 drivers/net/tun.c:1953
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1999
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61d/0xb90 fs/read_write.c:688
 ksys_write+0x150/0x270 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f71c515cece
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007f71c607ffb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f71c60806c0 RCX: 00007f71c515cece
RDX: 000000000000006e RSI: 0000200000000040 RDI: 00000000000000c8
RBP: 00007f71c5232b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f71c5416038 R14: 00007f71c5415fa0 R15: 00007ffcc237dd98
 </TASK>

The buggy address belongs to stack of task syz.1.4880/24782
 and is located at offset 100 in frame:
 dev_map_redirect_multi+0x0/0xa00 include/linux/skbuff.h:2833

This frame has 2 objects:
 [32, 40) 'iter.i'
 [64, 100) 'excluded_devices'

The buggy address belongs to a 8-page vmalloc region starting at 0xffffc900039f0000 allocated at copy_process+0x508/0x3cf0 kernel/fork.c:2050
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x63a37
memcg:ffff888033a20902
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff ffff888033a20902
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x29c2(GFP_NOWAIT|__GFP_HIGHMEM|__GFP_IO|__GFP_FS|__GFP_ZERO), pid 24774, tgid 24774 (syz.1.4877), ts 628925626739, free_ts 628905835634
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
 prep_new_page mm/page_alloc.c:1897 [inline]
 get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2485
 alloc_frozen_pages_noprof mm/mempolicy.c:2556 [inline]
 alloc_pages_noprof+0xa8/0x190 mm/mempolicy.c:2576
 vm_area_alloc_pages mm/vmalloc.c:3662 [inline]
 __vmalloc_area_node mm/vmalloc.c:3876 [inline]
 __vmalloc_node_range_noprof+0x79b/0x1730 mm/vmalloc.c:4064
 __vmalloc_node_noprof+0xc2/0x100 mm/vmalloc.c:4124
 alloc_thread_stack_node kernel/fork.c:355 [inline]
 dup_task_struct+0x228/0x9a0 kernel/fork.c:924
 copy_process+0x508/0x3cf0 kernel/fork.c:2050
 kernel_clone+0x248/0x8e0 kernel/fork.c:2654
 __do_sys_clone3 kernel/fork.c:2956 [inline]
 __se_sys_clone3+0x33c/0x360 kernel/fork.c:2935
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5808 tgid 5808 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
 __slab_free+0x263/0x2b0 mm/slub.c:5532
 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:4501 [inline]
 slab_alloc_node mm/slub.c:4830 [inline]
 kmem_cache_alloc_node_noprof+0x384/0x690 mm/slub.c:4882
 __alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
 alloc_skb_fclone include/linux/skbuff.h:1433 [inline]
 tcp_stream_alloc_skb+0x3f/0x580 net/ipv4/tcp.c:944
 tcp_sendmsg_locked+0x1375/0x5490 net/ipv4/tcp.c:1269
 tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1464
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 sock_write_iter+0x421/0x550 net/socket.c:1195
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61d/0xb90 fs/read_write.c:688
 ksys_write+0x150/0x270 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffffc900039f7000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc900039f7080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc900039f7100: f1 f1 f1 f1 00 f2 f2 f2 00 00 00 00 04 f3 f3 f3
                                                       ^
 ffffc900039f7180: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc900039f7200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================



	

	



	Crashes (2):
		
		

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			2026/02/22 21:28
			net-next
			8bf22c33e7a1
			6e7b5511
			.config
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			report
			
			
			info
			
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			ci-upstream-net-kasan-gce
			KASAN: stack-out-of-bounds Write in dev_map_redirect_multi
		

		
		

			2026/02/07 00:29
			net-next
			24cf78c73831
			f20fc9f9
			.config
			console log
			report
			
			
			info
			
				[disk image]
			
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				[kernel image]
			
			ci-upstream-net-kasan-gce
			KASAN: stack-out-of-bounds Write in dev_map_redirect_multi
		

		
		


* Struck through repros no longer work on HEAD.