KASAN: use-after-free Read in l2cap_sock_new_connection

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-6.1	KASAN: use-after-free Read in l2cap_sock_new_connection_cb				7	92d	216d	0/3	upstream: reported on 2024/11/01 14:54
upstream	KASAN: slab-use-after-free Read in l2cap_sock_new_connection_cb bluetooth				40	8d19h	228d	0/28	upstream: reported on 2024/10/21 08:46
 </TASK>
kobject_add_internal failed for hci2:201 with -EEXIST, don't try to register things with the same name in the same directory.
Bluetooth: hci2: failed to register connection device
==================================================================
BUG: KASAN: use-after-free in l2cap_sock_new_connection_cb+0x125/0x1c0 net/bluetooth/l2cap_sock.c:1491
Read of size 8 at addr ffff888061529548 by task kworker/u5:3/4176

CPU: 0 PID: 4176 Comm: kworker/u5:3 Not tainted 5.15.183-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: hci2 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 l2cap_sock_new_connection_cb+0x125/0x1c0 net/bluetooth/l2cap_sock.c:1491
 l2cap_connect_cfm+0x35d/0x10d0 net/bluetooth/l2cap_core.c:8278
 hci_connect_cfm include/net/bluetooth/hci_core.h:1505 [inline]
 le_conn_complete_evt+0xdaf/0x1590 net/bluetooth/hci_event.c:5429
 hci_le_conn_complete_evt net/bluetooth/hci_event.c:5454 [inline]
 hci_le_meta_evt+0x289/0x3b80 net/bluetooth/hci_event.c:6176
 hci_event_packet+0xe05/0x12f0 net/bluetooth/hci_event.c:6525
 hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5160
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Allocated by task 4176:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc mm/kasan/common.c:513 [inline]
 __kasan_kmalloc+0xb5/0xf0 mm/kasan/common.c:522
 kmalloc include/linux/slab.h:609 [inline]
 sk_prot_alloc+0xe7/0x210 net/core/sock.c:1864
 sk_alloc+0x2f/0x310 net/core/sock.c:1917
 l2cap_sock_alloc+0x33/0x200 net/bluetooth/l2cap_sock.c:1861
 l2cap_sock_new_connection_cb+0xd1/0x1c0 net/bluetooth/l2cap_sock.c:1476
 l2cap_connect_cfm+0x35d/0x10d0 net/bluetooth/l2cap_core.c:8278
 hci_connect_cfm include/net/bluetooth/hci_core.h:1505 [inline]
 le_conn_complete_evt+0xdaf/0x1590 net/bluetooth/hci_event.c:5429
 hci_le_conn_complete_evt net/bluetooth/hci_event.c:5454 [inline]
 hci_le_meta_evt+0x289/0x3b80 net/bluetooth/hci_event.c:6176
 hci_event_packet+0xe05/0x12f0 net/bluetooth/hci_event.c:6525
 hci_rx_work+0x255/0xa10 net/bluetooth/hci_core.c:5160
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Freed by task 5153:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:46
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:360
 ____kasan_slab_free+0xd5/0x110 mm/kasan/common.c:366
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:1705 [inline]
 slab_free_freelist_hook+0xea/0x170 mm/slub.c:1731
 slab_free mm/slub.c:3499 [inline]
 kfree+0xef/0x2a0 mm/slub.c:4559
 sk_prot_free net/core/sock.c:1900 [inline]
 __sk_destruct+0x55a/0x820 net/core/sock.c:1986
 l2cap_sock_cleanup_listen+0xda/0x270 net/bluetooth/l2cap_sock.c:1456
 l2cap_sock_release+0x59/0x1c0 net/bluetooth/l2cap_sock.c:1419
 __sock_release net/socket.c:649 [inline]
 sock_close+0xd5/0x240 net/socket.c:1336
 __fput+0x234/0x930 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 get_signal+0x1222/0x12c0 kernel/signal.c:2672
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff888061529000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1352 bytes inside of
 2048-byte region [ffff888061529000, ffff888061529800)
The buggy address belongs to the page:
page:ffffea0001854a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x61528
head:ffffea0001854a00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 0000000100000001 ffff888016842000
raw: 0000000000000000 0000000080080008 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 0xd2a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 4168, ts 71698156350, free_ts 25358115762
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x1b77/0x1c60 mm/page_alloc.c:4192
 __alloc_pages+0x1e1/0x470 mm/page_alloc.c:5466
 alloc_slab_page mm/slub.c:1775 [inline]
 allocate_slab mm/slub.c:1912 [inline]
 new_slab+0xc0/0x4b0 mm/slub.c:1975
 ___slab_alloc+0x81e/0xdf0 mm/slub.c:3008
 __slab_alloc mm/slub.c:3095 [inline]
 slab_alloc_node mm/slub.c:3186 [inline]
 __kmalloc_node_track_caller+0x1fc/0x3a0 mm/slub.c:4958
 kmalloc_reserve net/core/skbuff.c:356 [inline]
 pskb_expand_head+0x127/0x10f0 net/core/skbuff.c:1709
 netlink_trim+0x180/0x220 net/netlink/af_netlink.c:1293
 netlink_broadcast_filtered+0x7c/0x1170 net/netlink/af_netlink.c:1498
 netlink_broadcast net/netlink/af_netlink.c:1543 [inline]
 nlmsg_multicast include/net/netlink.h:1033 [inline]
 nlmsg_notify+0xec/0x1a0 net/netlink/af_netlink.c:2532
 __dev_notify_flags+0xde/0x2d0 net/core/dev.c:8887
 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8929
 do_setlink+0xc01/0x3980 net/core/rtnetlink.c:2779
 __rtnl_newlink net/core/rtnetlink.c:3450 [inline]
 rtnl_newlink+0x1419/0x17d0 net/core/rtnetlink.c:3572
 rtnetlink_rcv_msg+0x9b9/0xe60 net/core/rtnetlink.c:5650
 netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2489
 netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
 netlink_unicast+0x77c/0x920 net/netlink/af_netlink.c:1337
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x637/0x6c0 mm/page_alloc.c:3317
 free_unref_page+0x94/0x280 mm/page_alloc.c:3396
 free_contig_range+0x96/0xf0 mm/page_alloc.c:9385
 destroy_args+0xef/0x8b0 mm/debug_vm_pgtable.c:1018
 debug_vm_pgtable+0x318/0x370 mm/debug_vm_pgtable.c:1331
 do_one_initcall+0x1ee/0x680 init/main.c:1302
 do_initcall_level+0x137/0x1f0 init/main.c:1375
 do_initcalls+0x4b/0x90 init/main.c:1391
 kernel_init_freeable+0x3ce/0x560 init/main.c:1615
 kernel_init+0x19/0x1b0 init/main.c:1506
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Memory state around the buggy address:
 ffff888061529400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888061529480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888061529500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888061529580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888061529600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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