Re: [syzbot] [bluetooth?] KASAN: vmalloc-out-of-bounds Read in hci_devcd_dump

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in force_devcd_write

==================================================================
BUG: KASAN: slab-use-after-free in force_devcd_write+0x312/0x340 drivers/bluetooth/hci_vhci.c:327
Read of size 8 at addr ffff88802a361800 by task syz.0.616/8016

CPU: 0 UID: 0 PID: 8016 Comm: syz.0.616 Not tainted 6.15.0-syzkaller-13804-g939f15e640f1-dirty #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xcd/0x680 mm/kasan/report.c:521
 kasan_report+0xe0/0x110 mm/kasan/report.c:634
 force_devcd_write+0x312/0x340 drivers/bluetooth/hci_vhci.c:327
 full_proxy_write+0x13f/0x200 fs/debugfs/file.c:398
 vfs_write+0x29d/0x1150 fs/read_write.c:684
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f669c18e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f669d03c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f669c3b5fa0 RCX: 00007f669c18e969
RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f669c210ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f669c3b5fa0 R15: 00007ffcf3655198
 </TASK>

Allocated by task 6529:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:635
 misc_open+0x35d/0x420 drivers/char/misc.c:161
 chrdev_open+0x231/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x744/0x1c10 fs/open.c:964
 vfs_open+0x82/0x3f0 fs/open.c:1094
 do_open fs/namei.c:3887 [inline]
 path_openat+0x1de4/0x2cb0 fs/namei.c:4046
 do_filp_open+0x20b/0x470 fs/namei.c:4073
 do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x174/0x210 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6529:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2381 [inline]
 slab_free mm/slub.c:4643 [inline]
 kfree+0x2b4/0x4d0 mm/slub.c:4842
 vhci_release+0xbb/0xf0 drivers/bluetooth/hci_vhci.c:671
 __fput+0x402/0xb70 fs/file_table.c:465
 task_work_run+0x150/0x240 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x864/0x2bd0 kernel/exit.c:955
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1104
 get_signal+0x2673/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x790 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x84/0x110 kernel/entry/common.c:111
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x3f6/0x490 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802a361800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of
 freed 1024-byte region [ffff88802a361800, ffff88802a361c00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2a360
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b441dc0 ffffea00017efa00 dead000000000002
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b441dc0 ffffea00017efa00 dead000000000002
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000a8d801 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 79, tgid 79 (kworker/u8:4), ts 139345437556, free_ts 139048889741
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x1321/0x3890 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:4959
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab mm/slub.c:2619 [inline]
 new_slab+0x23b/0x330 mm/slub.c:2673
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3859
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3949
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x2f2/0x510 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 ieee802_11_parse_elems_full+0x1d7/0x3780 net/mac80211/parse.c:1013
 ieee802_11_parse_elems_crc net/mac80211/ieee80211_i.h:2414 [inline]
 ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2421 [inline]
 ieee80211_inform_bss+0x10b/0x1140 net/mac80211/scan.c:79
 rdev_inform_bss net/wireless/rdev-ops.h:418 [inline]
 cfg80211_inform_single_bss_data+0x8e7/0x1df0 net/wireless/scan.c:2367
 cfg80211_inform_bss_data+0x224/0x3bc0 net/wireless/scan.c:3222
 cfg80211_inform_bss_frame_data+0x26f/0x750 net/wireless/scan.c:3313
 ieee80211_bss_info_update+0x310/0xab0 net/mac80211/scan.c:226
 ieee80211_rx_bss_info net/mac80211/ibss.c:1094 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1573 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x1905/0x2fd0 net/mac80211/ibss.c:1600
 ieee80211_iface_process_skb net/mac80211/iface.c:1668 [inline]
 ieee80211_iface_work+0xbf4/0x1020 net/mac80211/iface.c:1722
page last free pid 3553 tgid 3553 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0x7fe/0x1180 mm/page_alloc.c:2706
 discard_slab mm/slub.c:2717 [inline]
 __put_partials+0x16d/0x1c0 mm/slub.c:3186
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4148 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_node_noprof+0x1d5/0x3b0 mm/slub.c:4249
 __alloc_skb+0x2b2/0x380 net/core/skbuff.c:660
 alloc_skb include/linux/skbuff.h:1336 [inline]
 nlmsg_new include/net/netlink.h:1041 [inline]
 mpls_netconf_notify_devconf+0x4a/0x110 net/mpls/af_mpls.c:1189
 mpls_dev_sysctl_unregister net/mpls/af_mpls.c:1432 [inline]
 mpls_dev_notify+0x726/0xa20 net/mpls/af_mpls.c:1641
 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
 call_netdevice_notifiers net/core/dev.c:2282 [inline]
 unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077
 ops_exit_rtnl_list net/core/net_namespace.c:188 [inline]
 ops_undo_list+0x8fc/0xab0 net/core/net_namespace.c:249
 cleanup_net+0x408/0x890 net/core/net_namespace.c:686
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3321 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402

Memory state around the buggy address:
 ffff88802a361700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802a361780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802a361800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88802a361880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802a361900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         939f15e6 Merge tag 'turbostat-2025.06.08' of git://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15687570580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6678e7c8a50af095
dashboard link: https://syzkaller.appspot.com/bug?extid=ac3c79181f6aecc5120c
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=172349d4580000