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BUG: KASAN: use-after-free in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: use-after-free in atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
BUG: KASAN: use-after-free in atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
BUG: KASAN: use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
BUG: KASAN: use-after-free in mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
Write of size 8 at addr ffff888131166d50 by task syz.0.72/565

CPU: 1 PID: 565 Comm: syz.0.72 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
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic64_try_cmpxchg_acquire include/asm-generic/atomic-instrumented.h:1515 [inline]
 atomic_long_try_cmpxchg_acquire include/asm-generic/atomic-long.h:443 [inline]
 __mutex_trylock_fast kernel/locking/mutex.c:173 [inline]
 mutex_lock+0x85/0xf0 kernel/locking/mutex.c:298
 pppol2tp_release+0x178/0x2b0 net/l2tp/l2tp_ppp.c:442
 __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
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f667d6c10d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcc5c56768 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffcc5c56850 RCX: 00007f667d6c10d9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000000816a R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2d220000 R11: 0000000000000246 R12: 00007ffcc5c56890
R13: 00007f667d948fac R14: 00000000000081aa R15: 00007f667d948fa0

Allocated by task 566:
 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 565:
 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
 pppol2tp_release+0x169/0x2b0 net/l2tp/l2tp_ppp.c:439
 __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
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff888131166c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 336 bytes inside of
 512-byte region [ffff888131166c00, ffff888131166e00)
The buggy address belongs to the page:
page:ffffea0004c45900 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x131164
head:ffffea0004c45900 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 0x1d2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 19, ts 33130925203, free_ts 30211312466
 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_track_caller+0x1e4/0x310 mm/slub.c:4541
 __kmalloc_reserve net/core/skbuff.c:144 [inline]
 __alloc_skb+0xdc/0x520 net/core/skbuff.c:212
 alloc_skb include/linux/skbuff.h:1126 [inline]
 nlmsg_new include/net/netlink.h:953 [inline]
 fdb_notify+0x78/0x130 net/bridge/br_fdb.c:745
 br_fdb_update+0x3f0/0x5b0 net/bridge/br_fdb.c:632
 br_handle_frame_finish+0x1ce/0x10f0 net/bridge/br_input.c:102
 nf_hook_bridge_pre net/bridge/br_input.c:259 [inline]
 br_handle_frame+0x406/0x8e0 net/bridge/br_input.c:363
 __netif_receive_skb_core+0xed5/0x30b0 net/core/dev.c:5307
 __netif_receive_skb_one_core net/core/dev.c:5411 [inline]
 __netif_receive_skb+0x72/0x280 net/core/dev.c:5527
 process_backlog+0x351/0x600 net/core/dev.c:6434
 napi_poll net/core/dev.c:6885 [inline]
 net_rx_action+0x48d/0xed0 net/core/dev.c:6955
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_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page_list+0x129/0x9c0 mm/page_alloc.c:3443
 release_pages+0xe41/0xe90 mm/swap.c:1103
 __pagevec_release+0x71/0xe0 mm/swap.c:1123
 pagevec_release include/linux/pagevec.h:88 [inline]
 shmem_undo_range+0x741/0x1740 mm/shmem.c:965
 shmem_truncate_range mm/shmem.c:1069 [inline]
 shmem_evict_inode+0x1dc/0x970 mm/shmem.c:1169
 evict+0x4a9/0x940 fs/inode.c:612
 iput_final fs/inode.c:1736 [inline]
 iput+0x654/0x7e0 fs/inode.c:1762
 dentry_unlink_inode+0x2d5/0x390 fs/dcache.c:378
 __dentry_kill+0x45b/0x660 fs/dcache.c:583
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x42/0x80 fs/dcache.c:883
 __fput+0x4bd/0x730 fs/file_table.c:294
 ____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:873

Memory state around the buggy address:
 ffff888131166c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888131166c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888131166d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888131166d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888131166e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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