KASAN: use-after-free Read in l2tp_tunnel_del_work

Status: premoderation: reported on 2026/06/23 09:58
Reported-by: syzbot+debdd4ed13bf7673952e@syzkaller.appspotmail.com
First crash: 134d, last: 8h41m
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Read in l2tp_tunnel_del_work 19 syz, C 121 2d14h 81d 0/2 upstream: reported C repro on 2026/08/15 11:07
android-5-15 KASAN: use-after-free Read in l2tp_tunnel_del_work 19 158 1d07h 130d 0/2 premoderation: reported on 2026/06/27 08:43
upstream KASAN: use-after-free Write in l2tp_tunnel_del_work (2) net 22 syz unreliable done 2 1362d 1428d 0/29 auto-obsoleted due to no activity on 2023/06/10 16:21
upstream KASAN: use-after-free Write in l2tp_tunnel_del_work net 22 1 1797d 1793d 0/29 auto-closed as invalid on 2022/04/01 19:17
upstream KASAN: slab-use-after-free Read in l2tp_tunnel_del_work net 19 syz, C done 99 848d 862d 27/29 fixed on 2024/08/14 03:44

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in hlist_unhashed include/linux/list.h:815 [inline]
BUG: KASAN: use-after-free in hlist_del_init include/linux/list.h:872 [inline]
BUG: KASAN: use-after-free in l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1232 [inline]
BUG: KASAN: use-after-free in l2tp_tunnel_del_work+0xcd/0x3d0 net/l2tp/l2tp_core.c:1273
Read of size 8 at addr ffff88810fb2b480 by task kworker/u4:0/7

CPU: 1 PID: 7 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 hlist_unhashed include/linux/list.h:815 [inline]
 hlist_del_init include/linux/list.h:872 [inline]
 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1232 [inline]
 l2tp_tunnel_del_work+0xcd/0x3d0 net/l2tp/l2tp_core.c:1273
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Allocated by task 2671:
 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:430 [inline]
 ____kasan_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 __kmalloc+0x19f/0x330 mm/slub.c:4038
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 l2tp_session_create+0x39/0xb60 net/l2tp/l2tp_core.c:1616
 pppol2tp_connect+0xbf5/0x1640 net/l2tp/l2tp_ppp.c:772
 __sys_connect_file net/socket.c:1867 [inline]
 __sys_connect+0x3ce/0x450 net/socket.c:1884
 __do_sys_connect net/socket.c:1894 [inline]
 __se_sys_connect net/socket.c:1891 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:1891
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 2671:
 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:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 l2tp_session_free net/l2tp/l2tp_core.c:168 [inline]
 l2tp_session_put+0xb2/0x1a0 net/l2tp/l2tp_core.c:193
 pppol2tp_ioctl+0x748/0x960 net/l2tp/l2tp_ppp.c:-1
 pppox_ioctl+0x1e1/0x440 drivers/net/ppp/pppox.c:110
 sock_do_ioctl+0xda/0x380 net/socket.c:1068
 sock_ioctl+0x472/0x740 net/socket.c:1208
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88810fb2b400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 128 bytes inside of
 512-byte region [ffff88810fb2b400, ffff88810fb2b600)
The buggy address belongs to the page:
page:ffffea00043eca00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10fb28
head:ffffea00043eca00 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 9, ts 77837442349, free_ts 77805347387
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc+0x1f9/0x330 mm/slub.c:4034
 kmalloc include/linux/slab.h:560 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:154
 ip6_route_info_create+0x4c7/0x1450 net/ipv6/route.c:3675
 addrconf_f6i_alloc+0x19c/0x3f0 net/ipv6/route.c:4474
 ipv6_add_addr+0x442/0xd90 net/ipv6/addrconf.c:1119
 addrconf_add_linklocal+0x209/0x660 net/ipv6/addrconf.c:3271
 addrconf_addr_gen+0x53f/0x6a0 net/ipv6/addrconf.c:3402
 addrconf_dev_config+0x299/0x510 net/ipv6/addrconf.c:3454
 addrconf_notify+0x9d8/0xea0 net/ipv6/addrconf.c:3687
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x390 mm/page_alloc.c:5454
 kfree+0x1e4/0x270 mm/slub.c:4193
 tipc_nametbl_stop+0x120b/0x1270 net/tipc/name_table.c:917
 tipc_exit_net+0x99/0x150 net/tipc/core.c:118
 ops_exit_list net/core/net_namespace.c:185 [inline]
 cleanup_net+0x589/0xb80 net/core/net_namespace.c:609
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Memory state around the buggy address:
 ffff88810fb2b380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88810fb2b400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810fb2b480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88810fb2b500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810fb2b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (901):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/11/04 03:09 android13-5.10-lts f61a392235e0 5af5b6c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/04 03:09 android13-5.10-lts f61a392235e0 5af5b6c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/03 21:05 android13-5.10-lts f61a392235e0 e2d35131 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/03 20:04 android13-5.10-lts f61a392235e0 e2d35131 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/03 12:23 android13-5.10-lts f61a392235e0 e2d35131 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/03 11:00 android13-5.10-lts f61a392235e0 6969b601 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/03 04:15 android13-5.10-lts f61a392235e0 6969b601 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/02 17:47 android13-5.10-lts f61a392235e0 6969b601 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/02 10:36 android13-5.10-lts f61a392235e0 6969b601 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/02 05:50 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/02 02:42 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/01 19:48 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/01 17:05 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/01 08:31 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/01 07:31 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/01 02:23 android13-5.10-lts f61a392235e0 25a0ae84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/11/01 00:44 android13-5.10-lts f61a392235e0 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/31 21:52 android13-5.10-lts f61a392235e0 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/31 14:59 android13-5.10-lts f61a392235e0 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/31 09:09 android13-5.10-lts f61a392235e0 2041d3f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/31 06:58 android13-5.10-lts f61a392235e0 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/31 02:45 android13-5.10-lts f61a392235e0 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/31 01:00 android13-5.10-lts f61a392235e0 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 19:17 android13-5.10-lts f61a392235e0 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 17:12 android13-5.10-lts f61a392235e0 0ec395f8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 15:14 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 12:43 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 06:25 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 03:56 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/30 01:26 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/29 20:07 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/29 18:14 android13-5.10-lts f61a392235e0 b498adee .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/29 16:57 android13-5.10-lts f61a392235e0 b1d00f76 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/29 13:39 android13-5.10-lts f61a392235e0 b1d00f76 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/29 03:45 android13-5.10-lts f61a392235e0 b1d00f76 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/28 04:00 android13-5.10-lts f61a392235e0 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/28 02:46 android13-5.10-lts f61a392235e0 96923c60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/27 14:20 android13-5.10-lts f61a392235e0 168cb7a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/26 18:53 android13-5.10-lts f61a392235e0 168cb7a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/26 12:42 android13-5.10-lts f61a392235e0 168cb7a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/26 08:35 android13-5.10-lts f61a392235e0 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/10/26 03:33 android13-5.10-lts f61a392235e0 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/09/29 11:40 android13-5.10-lts 340d402887d3 7bf4ea23 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in l2tp_tunnel_del_work
2026/09/26 18:53 android13-5.10-lts c5d8ec7afea2 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 general protection fault in l2tp_tunnel_del_work
* Struck through repros no longer work on HEAD.