KASAN: use-after-free Write in hci_conn_hash_flush

Status: auto-obsoleted due to no activity on 2025/09/30 18:03
Reported-by: syzbot+75e955b086f4b80b9b32@syzkaller.appspotmail.com
First crash: 557d, last: 402d
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Write in hci_conn_hash_flush (2) 22 1 280d 280d 0/3 auto-obsoleted due to no activity on 2026/01/30 19:02
linux-6.1 KASAN: use-after-free Write in hci_conn_hash_flush (3) 22 syz 1 34d 70d 0/3 upstream: reported syz repro on 2026/05/20 21:49
upstream KASAN: slab-use-after-free Read in hci_conn_hash_flush bluetooth 22 syz, C error 3511 1150d 1244d 22/29 fixed on 2023/07/01 16:05

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in hci_conn_unlink net/bluetooth/hci_conn.c:1084 [inline]
BUG: KASAN: use-after-free in hci_conn_hash_flush+0x1d4/0x2a0 net/bluetooth/hci_conn.c:2509
Write of size 8 at addr ffff88802f3e8ab0 by task syz.4.387/6436

CPU: 1 PID: 6436 Comm: syz.4.387 Not tainted 6.1.134-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0x15f/0x4f0 mm/kasan/report.c:427
 kasan_report+0x136/0x160 mm/kasan/report.c:531
 hci_conn_unlink net/bluetooth/hci_conn.c:1084 [inline]
 hci_conn_hash_flush+0x1d4/0x2a0 net/bluetooth/hci_conn.c:2509
 hci_dev_close_sync+0x9a9/0xfc0 net/bluetooth/hci_sync.c:5178
 hci_dev_do_close net/bluetooth/hci_core.c:510 [inline]
 hci_unregister_dev+0x207/0x500 net/bluetooth/hci_core.c:2707
 vhci_release+0x7f/0xd0 drivers/bluetooth/hci_vhci.c:573
 __fput+0x3f6/0x8d0 fs/file_table.c:320
 task_work_run+0x246/0x300 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0xa6e/0x26a0 kernel/exit.c:871
 do_group_exit+0x202/0x2b0 kernel/exit.c:1021
 get_signal+0x16cb/0x17a0 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb3/0x12a0 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
 do_syscall_64+0x47/0x80 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc528f8dd6b
Code: Unable to access opcode bytes at 0x7fc528f8dd41.
RSP: 002b:00007fc529e78d60 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: 0000000000000000 RBX: 00007fc529e78df0 RCX: 00007fc528f8dd6b
RDX: 00007fc529e78f00 RSI: 0000000000004c04 RDI: 0000000000000008
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000001045
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc529e78f00
R13: 0000000000000000 R14: 00007fc5291b5fa0 R15: 00007ffcc51b8478
 </TASK>

Allocated by task 4680:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:383
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 hci_conn_add+0xb7/0x1390 net/bluetooth/hci_conn.c:989
 hci_connect_sco+0x86/0x330 net/bluetooth/hci_conn.c:1629
 sco_connect net/bluetooth/sco.c:280 [inline]
 sco_sock_connect+0x2c3/0x960 net/bluetooth/sco.c:616
 __sys_connect_file net/socket.c:2011 [inline]
 __sys_connect+0x2c9/0x300 net/socket.c:2028
 __do_sys_connect net/socket.c:2038 [inline]
 __se_sys_connect net/socket.c:2035 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:2035
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0x80 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 6436:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0xd6/0x120 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook mm/slub.c:1750 [inline]
 slab_free mm/slub.c:3661 [inline]
 __kmem_cache_free+0x25c/0x3c0 mm/slub.c:3674
 device_release+0x91/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:681 [inline]
 kobject_release lib/kobject.c:712 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x224/0x460 lib/kobject.c:729
 hci_conn_cleanup+0x5a0/0x740 net/bluetooth/hci_conn.c:172
 hci_conn_del+0x417/0x6c0 net/bluetooth/hci_conn.c:1151
 hci_conn_hash_flush+0x205/0x2a0 net/bluetooth/hci_conn.c:2510
 hci_dev_close_sync+0x9a9/0xfc0 net/bluetooth/hci_sync.c:5178
 hci_dev_do_close net/bluetooth/hci_core.c:510 [inline]
 hci_unregister_dev+0x207/0x500 net/bluetooth/hci_core.c:2707
 vhci_release+0x7f/0xd0 drivers/bluetooth/hci_vhci.c:573
 __fput+0x3f6/0x8d0 fs/file_table.c:320
 task_work_run+0x246/0x300 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0xa6e/0x26a0 kernel/exit.c:871
 do_group_exit+0x202/0x2b0 kernel/exit.c:1021
 get_signal+0x16cb/0x17a0 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb3/0x12a0 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
 do_syscall_64+0x47/0x80 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88802f3e8000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 2736 bytes inside of
 4096-byte region [ffff88802f3e8000, ffff88802f3e9000)

The buggy address belongs to the physical page:
page:ffffea0000bcfa00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2f3e8
head:ffffea0000bcfa00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00013c0800 dead000000000002 ffff888017c42140
raw: 0000000000000000 0000000000040004 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 4680, tgid 4677 (syz.3.61), ts 112091850828, free_ts 112064365846
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x18d/0x1b0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x3731/0x38d0 mm/page_alloc.c:4328
 __alloc_pages+0x28d/0x770 mm/page_alloc.c:5606
 alloc_slab_page+0x6a/0x150 mm/slub.c:1794
 allocate_slab mm/slub.c:1939 [inline]
 new_slab+0x84/0x2d0 mm/slub.c:1992
 ___slab_alloc+0xc20/0x1270 mm/slub.c:3180
 __slab_alloc mm/slub.c:3279 [inline]
 slab_alloc_node mm/slub.c:3364 [inline]
 __kmem_cache_alloc_node+0x19f/0x260 mm/slub.c:3437
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 hci_conn_add+0xb7/0x1390 net/bluetooth/hci_conn.c:989
 hci_connect_sco+0x86/0x330 net/bluetooth/hci_conn.c:1629
 sco_connect net/bluetooth/sco.c:280 [inline]
 sco_sock_connect+0x2c3/0x960 net/bluetooth/sco.c:616
 __sys_connect_file net/socket.c:2011 [inline]
 __sys_connect+0x2c9/0x300 net/socket.c:2028
 __do_sys_connect net/socket.c:2038 [inline]
 __se_sys_connect net/socket.c:2035 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:2035
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0x80 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x12a6/0x15b0 mm/page_alloc.c:3384
 free_unref_page+0x33/0x3e0 mm/page_alloc.c:3479
 free_slab mm/slub.c:2031 [inline]
 discard_slab mm/slub.c:2037 [inline]
 __unfreeze_partials+0x1b7/0x210 mm/slub.c:2586
 put_cpu_partial+0x17b/0x250 mm/slub.c:2662
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x156/0x170 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1f/0x70 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x52/0x3a0 mm/slab.h:737
 kmem_cache_alloc_bulk+0x3a2/0x4d0 mm/slub.c:3854
 mt_alloc_bulk lib/maple_tree.c:157 [inline]
 mas_alloc_nodes+0x3df/0x800 lib/maple_tree.c:1299
 mas_node_count_gfp lib/maple_tree.c:1359 [inline]
 mas_preallocate+0x12d/0x350 lib/maple_tree.c:5805
 __mmap_region mm/mmap.c:2753 [inline]
 mmap_region+0xfef/0x2660 mm/mmap.c:2904
 do_mmap+0x8c5/0xf60 mm/mmap.c:1424
 vm_mmap_pgoff+0x1ca/0x2d0 mm/util.c:520
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0x80 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
 ffff88802f3e8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802f3e8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802f3e8a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff88802f3e8b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802f3e8b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/04/21 05:07 linux-6.1.y 420102835862 2a20f901 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in hci_conn_hash_flush
2025/03/30 04:43 linux-6.1.y 8e60a714ba3b d3999433 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in hci_conn_hash_flush
2025/06/22 18:02 linux-6.1.y 58485ff1a74f d6cdfb8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in hci_conn_hash_flush
2025/01/19 00:35 linux-6.1.y 60ceadf9247e f2cb035c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Write in hci_conn_hash_flush
* Struck through repros no longer work on HEAD.