================================================================== BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156 Read of size 4 at addr ffff888104de4800 by task syz-executor152/298 CPU: 0 PID: 298 Comm: syz-executor152 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 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_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308 pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156 pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:435 __sock_release net/socket.c:597 [inline] sock_close+0xb8/0x200 net/socket.c:1287 __fput+0x2dc/0x730 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa7c/0x24e0 kernel/exit.c:879 __do_sys_exit kernel/exit.c:962 [inline] __se_sys_exit kernel/exit.c:960 [inline] __x64_sys_exit+0x40/0x40 kernel/exit.c:960 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f601acc1d79 Code: Unable to access opcode bytes at RIP 0x7f601acc1d4f. RSP: 002b:00007ffc5ee39ed8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c RAX: ffffffffffffffda RBX: 0000200000000040 RCX: 00007f601acc1d79 RDX: 00007f601acd3557 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000023800000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc5ee3a0f8 R13: 0000000000000002 R14: 00007f601ad52ca0 R15: 0000000000000002 Allocated by task 297: 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 7: 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 l2tp_session_delete+0x3a9/0x4a0 net/l2tp/l2tp_core.c:1589 l2tp_tunnel_closeall net/l2tp/l2tp_core.c:1235 [inline] l2tp_tunnel_del_work+0x180/0x3d0 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 The buggy address belongs to the object at ffff888104de4800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff888104de4800, ffff888104de4a00) The buggy address belongs to the page: page:ffffea0004137900 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x104de4 head:ffffea0004137900 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 0000000000000000 0000000100000001 ffff888100043080 raw: 0000000000000000 0000000080100010 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, ts 1570315362, free_ts 1569543803 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_array include/linux/slab.h:595 [inline] kcalloc include/linux/slab.h:606 [inline] __tty_alloc_driver+0x31f/0x4c0 drivers/tty/tty_io.c:3348 alloc_tty_driver include/linux/tty_driver.h:355 [inline] vty_init+0xea/0x354 drivers/tty/vt/vt.c:3611 tty_init+0x138/0x177 drivers/tty/tty_io.c:3606 chr_dev_init+0x25e/0x265 drivers/char/mem.c:1097 do_one_initcall+0x205/0x5e0 init/main.c:1172 do_initcall_level+0x174/0x2dc init/main.c:1245 do_initcalls+0x50/0x92 init/main.c:1261 do_basic_setup+0x88/0x8f init/main.c:1281 kernel_init_freeable+0x28c/0x3c3 init/main.c:1485 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 free_pages+0x82/0x90 mm/page_alloc.c:5465 __stack_depot_save+0x492/0x4c0 lib/stackdepot.c:359 kasan_save_stack mm/kasan/common.c:39 [inline] kasan_set_track+0x5b/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 cleanup_uevent_env+0x38/0x40 lib/kobject_uevent.c:274 call_usermodehelper_freeinfo kernel/umh.c:44 [inline] call_usermodehelper_exec+0x16b/0x490 kernel/umh.c:452 kobject_uevent_env+0x659/0x700 lib/kobject_uevent.c:633 kobject_uevent+0x1d/0x30 lib/kobject_uevent.c:657 device_add+0x7d2/0xc00 drivers/base/core.c:3254 device_create_groups_vargs drivers/base/core.c:3960 [inline] device_create+0x26c/0x300 drivers/base/core.c:4002 Memory state around the buggy address: ffff888104de4700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888104de4780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888104de4800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888104de4880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888104de4900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ WARNING: CPU: 0 PID: 298 at net/l2tp/l2tp_ppp.c:156 pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156 Modules linked in: CPU: 0 PID: 298 Comm: syz-executor152 Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156 Code: 5d c3 e8 cc f7 34 fd be 02 00 00 00 eb 0a e8 c0 f7 34 fd be 01 00 00 00 4c 89 f7 e8 43 73 0e fe e9 0f ff ff ff e8 a9 f7 34 fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 98 f7 34 fd 4c 89 f7 be 03 RSP: 0018:ffffc90000b47c40 EFLAGS: 00010293 RAX: ffffffff842fbf17 RBX: ffff88811c2c2000 RCX: ffff88811b716400 RDX: 0000000000000000 RSI: 000000001edea500 RDI: 000000000c04eb7d RBP: ffffc90000b47c60 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffffbfff0dcf848 R12: dffffc0000000000 R13: dffffc0000000000 R14: 000000001edea500 R15: ffff888104de4800 FS: 0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f601acd34f0 CR3: 000000010d550000 CR4: 00000000003506b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: pppol2tp_release+0x150/0x2b0 net/l2tp/l2tp_ppp.c:435 __sock_release net/socket.c:597 [inline] sock_close+0xb8/0x200 net/socket.c:1287 __fput+0x2dc/0x730 fs/file_table.c:281 ____fput+0x15/0x20 fs/file_table.c:314 task_work_run+0x127/0x190 kernel/task_work.c:189 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa7c/0x24e0 kernel/exit.c:879 __do_sys_exit kernel/exit.c:962 [inline] __se_sys_exit kernel/exit.c:960 [inline] __x64_sys_exit+0x40/0x40 kernel/exit.c:960 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x61/0xcb RIP: 0033:0x7f601acc1d79 Code: Unable to access opcode bytes at RIP 0x7f601acc1d4f. RSP: 002b:00007ffc5ee39ed8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c RAX: ffffffff