================================================================== BUG: KASAN: use-after-free in pppol2tp_sock_to_session+0x1a0/0x1b0 net/l2tp/l2tp_ppp.c:156 Read of size 4 at addr ffff88810b459800 by task syz-executor116/299 CPU: 0 PID: 299 Comm: syz-executor116 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 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: 0033:0x7f5faa7a3859 Code: Unable to access opcode bytes at RIP 0x7f5faa7a382f. RSP: 002b:00007f5faa785118 EFLAGS: 00000246 ORIG_RAX: 000000000000003c RAX: ffffffffffffffda RBX: 00007f5faa852b48 RCX: 00007f5faa7a3859 RDX: 00007f5faa7859c8 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 00007f5faa852b40 R08: 0000000000000000 R09: 0000000023800000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5faa81e028 R13: 0000200000000040 R14: 0000200000000908 R15: 0000200000000900 Allocated by task 298: 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 ffff88810b459800 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff88810b459800, ffff88810b459a00) The buggy address belongs to the page: page:ffffea00042d1600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10b458 head:ffffea00042d1600 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea00042d0f00 0000000200000002 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 7, ts 2461908837, free_ts 2461302669 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] kmem_cache_alloc_trace+0x1a8/0x2e0 mm/slub.c:2977 kmem_cache_alloc_node_trace include/linux/slab.h:443 [inline] kmalloc_node include/linux/slab.h:573 [inline] kzalloc_node include/linux/slab.h:678 [inline] sbitmap_queue_init_node+0x6af/0xf20 lib/sbitmap.c:381 bt_alloc block/blk-mq-tag.c:470 [inline] blk_mq_init_bitmap_tags block/blk-mq-tag.c:482 [inline] blk_mq_init_tags+0x1a2/0x380 block/blk-mq-tag.c:550 blk_mq_alloc_rq_map+0x84/0x1b0 block/blk-mq.c:2441 blk_mq_sched_alloc_tags block/blk-mq-sched.c:537 [inline] blk_mq_init_sched+0x20e/0xb70 block/blk-mq-sched.c:588 elevator_init_mq+0x353/0x470 block/elevator.c:688 __device_add_disk+0x6d/0x1010 block/genhd.c:784 device_add_disk+0x2a/0x40 block/genhd.c:844 sd_probe+0xb7b/0x10e0 drivers/scsi/sd.c:3499 really_probe+0x3bf/0xa60 drivers/base/dd.c:562 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 mm/kasan/common.c:45 [inline] set_alloc_info mm/kasan/common.c:430 [inline] __kasan_slab_alloc+0xc9/0xe0 mm/kasan/common.c:463 kasan_slab_alloc include/linux/kasan.h:244 [inline] slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580 slab_alloc_node mm/slub.c:2952 [inline] slab_alloc mm/slub.c:2960 [inline] kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965 kmem_cache_zalloc include/linux/slab.h:657 [inline] __kernfs_new_node+0xe1/0x670 fs/kernfs/dir.c:662 kernfs_new_node+0x150/0x260 fs/kernfs/dir.c:739 kernfs_create_link+0xa4/0x200 fs/kernfs/symlink.c:39 sysfs_do_create_link_sd+0x8a/0x110 fs/sysfs/symlink.c:44 sysfs_do_create_link fs/sysfs/symlink.c:80 [inline] sysfs_create_link+0x68/0x80 fs/sysfs/symlink.c:92 device_add_class_symlinks+0x155/0x2a0 drivers/base/core.c:3000 device_add+0x4d2/0xc00 drivers/base/core.c:3221 device_register+0x1d/0x20 drivers/base/core.c:3347 __mdiobus_register+0x215/0x7d0 drivers/net/phy/mdio_bus.c:552 Memory state around the buggy address: ffff88810b459700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88810b459780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88810b459800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88810b459880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88810b459900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ WARNING: CPU: 1 PID: 299 at net/l2tp/l2tp_ppp.c:156 pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156 Modules linked in: CPU: 1 PID: 299 Comm: syz-executor116 Tainted: G B syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 RIP: 0010:pppol2tp_sock_to_session+0x167/0x1b0 net/l2tp/l2tp_ppp.c:156 Code: 5d c3 e8 2c 5a 35 fd be 02 00 00 00 eb 0a e8 20 5a 35 fd be 01 00 00 00 4c 89 f7 e8 63 ca 0e fe e9 0f ff ff ff e8 09 5a 35 fd <0f> 0b 48 89 df e8 ef 00 00 00 eb bd e8 f8 59 35 fd 4c 89 f7 be 03 RSP: 0018:ffffc9000098fc40 EFLAGS: 00010293 RAX: ffffffff842f5aa7 RBX: ffff88811e164000 RCX: ffff88811da76400 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000c04eb7d RBP: ffffc9000098fc60 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffffbfff0dcf848 R12: dffffc0000000000 R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88810b459800 FS: 0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006aa5b0 CR3: 000000010d488000 CR4: 00000000003506a0 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: 0033:0x7f5faa7a3859 Code: Unable to access opcode bytes at RIP 0x7f5faa7a382f. RSP: 002b:00007f5faa785118 EFLAGS: 00000246 ORIG_RAX: 000000000000003c