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KASAN: use-after-free Read in macsec_get_iflink (3)

Status: upstream: reported C repro on 2026/01/29 14:26
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+1fbdecf70f249adc9e35@syzkaller.appspotmail.com
First crash: 1d13h, last: 1d13h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/01/29 lts (merge base) 278455a82245 C [report] KASAN: use-after-free Read in macsec_get_iflink
2026/01/29 upstream (ToT) 8dfce8991b95 C Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in macsec_get_iflink (2) 19 C 7 12d 454d 0/2 upstream: reported C repro on 2024/11/02 16:17
android-5-15 KASAN: use-after-free Read in macsec_get_iflink (2) 19 1 286d 286d 0/2 auto-obsoleted due to no activity on 2025/07/19 01:07
android-5-10 KASAN: use-after-free Read in macsec_get_iflink 19 syz error 2 608d 735d 0/2 auto-obsoleted due to no activity on 2024/08/30 07:40
android-5-15 KASAN: use-after-free Read in macsec_get_iflink 19 1 1011d 1011d 0/2 auto-obsoleted due to no activity on 2023/07/24 21:03
upstream KASAN: use-after-free Read in macsec_get_iflink net 19 1 1348d 1344d 22/29 fixed on 2023/02/24 13:50

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in macsec_get_iflink+0x6d/0x70 drivers/net/macsec.c:3677
Read of size 4 at addr ffff8881113ee0d0 by task kworker/u4:1/10

CPU: 1 PID: 10 Comm: kworker/u4:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 macsec_get_iflink+0x6d/0x70 drivers/net/macsec.c:3677
 dev_get_iflink+0x70/0xc0 net/core/dev.c:711
 default_operstate net/core/link_watch.c:41 [inline]
 rfc2863_policy+0x124/0x2b0 net/core/link_watch.c:53
 linkwatch_do_dev+0x3b/0x160 net/core/link_watch.c:160
 linkwatch_forget_dev+0x170/0x180 net/core/link_watch.c:238
 netdev_run_todo+0x2b8/0x9b0 net/core/dev.c:10687
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:112
 default_device_exit_batch+0x363/0x3c0 net/core/dev.c:11684
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x60a/0xae0 net/core/net_namespace.c:599
 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 372:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 ____kasan_kmalloc mm/kasan/common.c:512 [inline]
 __kasan_kmalloc+0xda/0x110 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 __kmalloc+0x13d/0x2c0 mm/slub.c:4436
 __kmalloc_node include/linux/slab.h:487 [inline]
 kmalloc_node include/linux/slab.h:642 [inline]
 kvmalloc_node+0x211/0x320 mm/util.c:621
 kvmalloc include/linux/mm.h:862 [inline]
 kvzalloc include/linux/mm.h:870 [inline]
 alloc_netdev_mqs+0x8d/0xc90 net/core/dev.c:10900
 rtnl_create_link+0x2ef/0x9d0 net/core/rtnetlink.c:3232
 veth_newlink+0x2e5/0xe30 drivers/net/veth.c:1667
 __rtnl_newlink net/core/rtnetlink.c:3524 [inline]
 rtnl_newlink+0x133a/0x1a30 net/core/rtnetlink.c:3572
 rtnetlink_rcv_msg+0xa4b/0xce0 net/core/rtnetlink.c:5650
 netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2511
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5668
 netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
 netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1348
 netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1922
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 __sys_sendto+0x46d/0x620 net/socket.c:2063
 __do_sys_sendto net/socket.c:2075 [inline]
 __se_sys_sendto net/socket.c:2071 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2071
 x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 10:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kfree+0xc4/0x270 mm/slub.c:4588
 kvfree+0x35/0x40 mm/util.c:661
 netdev_freemem+0x3f/0x60 net/core/dev.c:10854
 netdev_release+0x7f/0xb0 net/core/net-sysfs.c:1903
 device_release+0x96/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:713 [inline]
 kobject_release lib/kobject.c:744 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x18a/0x270 lib/kobject.c:761
 netdev_run_todo+0x834/0x9b0 net/core/dev.c:10710
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:112
 default_device_exit_batch+0x363/0x3c0 net/core/dev.c:11684
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x60a/0xae0 net/core/net_namespace.c:599
 process_one_work+0x6be/0xba0 kernel/workqueue.c:2325
 worker_thread+0xa59/0x1200 kernel/workqueue.c:2472
 kthread+0x411/0x500 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

The buggy address belongs to the object at ffff8881113ee000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 208 bytes inside of
 4096-byte region [ffff8881113ee000, ffff8881113ef000)
The buggy address belongs to the page:
page:ffffea000444fa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1113e8
head:ffffea000444fa00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043380
raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
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 109, ts 5262049499, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x2d3a/0x2dc0 mm/page_alloc.c:4485
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5808
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa1/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x381/0x810 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc_trace+0x146/0x270 mm/slub.c:3272
 kmalloc include/linux/slab.h:619 [inline]
 kzalloc include/linux/slab.h:750 [inline]
 kernfs_iop_get_link+0x66/0x600 fs/kernfs/symlink.c:136
 vfs_readlink+0x179/0x3e0 fs/namei.c:5089
 do_readlinkat+0x251/0x490 fs/stat.c:454
 __do_sys_readlink fs/stat.c:475 [inline]
 __se_sys_readlink fs/stat.c:472 [inline]
 __x64_sys_readlink+0x7f/0x90 fs/stat.c:472
 x64_sys_call+0x93c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881113edf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881113ee000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881113ee080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8881113ee100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881113ee180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_macvtap: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_macvtap: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): macsec0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_vlan: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vlan0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vlan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_vlan: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_vlan: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vlan0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vlan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_macvtap: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_macvtap: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_macvtap: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_macvtap: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): macsec0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_vlan: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_vlan: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vlan0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): vlan1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_virt_wifi: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_vlan: link becomes ready

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/29 14:24 android13-5.15-lts 7e1070528954 aeb6fdd5 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in macsec_get_iflink
* Struck through repros no longer work on HEAD.