[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in force_devcd_write

Hello,

syzbot found the following issue on:

HEAD commit: 48f506ad0b68 Merge tag 'soc-fixes-6.13-2' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13f19f30580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c22efbd20f8da769
dashboard link: https://syzkaller.appspot.com/bug?extid=bc71245e56f06e3127b7
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17df9fe8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f42f936a7d8d/disk-48f506ad.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5f5d9512f350/vmlinux-48f506ad.xz
kernel image: https://storage.googleapis.com/syzbot-assets/08855819fbb0/bzImage-48f506ad.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

==================================================================
BUG: KASAN: slab-use-after-free in force_devcd_write+0x31f/0x350 drivers/bluetooth/hci_vhci.c:327
Read of size 8 at addr ffff88805dfd8800 by task syz.0.616/6633

CPU: 1 UID: 0 PID: 6633 Comm: syz.0.616 Not tainted 6.13.0-rc3-syzkaller-00289-g48f506ad0b68 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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:378 [inline]
print_report+0xc3/0x620 mm/kasan/report.c:489
kasan_report+0xd9/0x110 mm/kasan/report.c:602
force_devcd_write+0x31f/0x350 drivers/bluetooth/hci_vhci.c:327
full_proxy_write+0xfb/0x1b0 fs/debugfs/file.c:356
vfs_write+0x24c/0x1150 fs/read_write.c:677
ksys_write+0x12b/0x250 fs/read_write.c:731
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4c25785d29
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:00007fffacf7c428 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4c25975fa0 RCX: 00007f4c25785d29
RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f4c25801aa8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4c25975fa0 R14: 00007f4c25975fa0 R15: 00000000000018c5
</TASK>

Allocated by task 5945:
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:901 [inline]
kzalloc_noprof include/linux/slab.h:1037 [inline]
vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:634
misc_open+0x35a/0x420 drivers/char/misc.c:165
chrdev_open+0x237/0x6a0 fs/char_dev.c:414
do_dentry_open+0xf59/0x1ea0 fs/open.c:945
vfs_open+0x82/0x3f0 fs/open.c:1075
do_open fs/namei.c:3828 [inline]
path_openat+0x1e6a/0x2d60 fs/namei.c:3987
do_filp_open+0x20c/0x470 fs/namei.c:4014
do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
do_sys_open fs/open.c:1417 [inline]
__do_sys_openat fs/open.c:1433 [inline]
__se_sys_openat fs/open.c:1428 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1428
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5945:
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:582
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:2353 [inline]
slab_free mm/slub.c:4613 [inline]
kfree+0x14f/0x4b0 mm/slub.c:4761
vhci_release+0xbb/0xf0 drivers/bluetooth/hci_vhci.c:670
__fput+0x3f8/0xb60 fs/file_table.c:450
task_work_run+0x14e/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0xad8/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3017
arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88805dfd8800
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of
freed 1024-byte region [ffff88805dfd8800, ffff88805dfd8c00)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5dfd8
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 ffff88801ac41dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 00fff00000000040 ffff88801ac41dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000
head: 00fff00000000003 ffffea000177f601 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5606, tgid 5606 (dhcpcd), ts 41765829328, free_ts 41751365215
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1558
prep_new_page mm/page_alloc.c:1566 [inline]
get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3476
__alloc_pages_noprof+0x223/0x25b0 mm/page_alloc.c:4753
alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2269
alloc_slab_page mm/slub.c:2423 [inline]
allocate_slab mm/slub.c:2589 [inline]
new_slab+0x2c9/0x410 mm/slub.c:2642
___slab_alloc+0xce2/0x1650 mm/slub.c:3830
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3920
__slab_alloc_node mm/slub.c:3995 [inline]
slab_alloc_node mm/slub.c:4156 [inline]
__do_kmalloc_node mm/slub.c:4297 [inline]
__kmalloc_noprof+0x2de/0x4f0 mm/slub.c:4310
kmalloc_noprof include/linux/slab.h:905 [inline]
load_elf_phdrs+0x103/0x210 fs/binfmt_elf.c:532
load_elf_binary+0x14c6/0x4ed0 fs/binfmt_elf.c:961
search_binary_handler fs/exec.c:1748 [inline]
exec_binprm fs/exec.c:1790 [inline]
bprm_execve fs/exec.c:1842 [inline]
bprm_execve+0x703/0x19b0 fs/exec.c:1818
do_execveat_common.isra.0+0x4f1/0x630 fs/exec.c:1949
do_execve fs/exec.c:2023 [inline]
__do_sys_execve fs/exec.c:2099 [inline]
__se_sys_execve fs/exec.c:2094 [inline]
__x64_sys_execve+0x8c/0xb0 fs/exec.c:2094
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5498 tgid 5498 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1127 [inline]
free_unref_page+0x661/0x1080 mm/page_alloc.c:2659
__put_partials+0x14c/0x170 mm/slub.c:3157
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4e/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:4119 [inline]
slab_alloc_node mm/slub.c:4168 [inline]
kmem_cache_alloc_node_noprof+0x1ca/0x3b0 mm/slub.c:4220
__alloc_skb+0x2b3/0x380 net/core/skbuff.c:668
alloc_skb include/linux/skbuff.h:1323 [inline]
netlink_alloc_large_skb+0x69/0x130 net/netlink/af_netlink.c:1196
netlink_sendmsg+0x689/0xd70 net/netlink/af_netlink.c:1866
sock_sendmsg_nosec net/socket.c:711 [inline]
__sock_sendmsg net/socket.c:726 [inline]
__sys_sendto+0x488/0x4f0 net/socket.c:2197
__do_sys_sendto net/socket.c:2204 [inline]
__se_sys_sendto net/socket.c:2200 [inline]
__x64_sys_sendto+0xe0/0x1c0 net/socket.c:2200
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff88805dfd8700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805dfd8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805dfd8800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805dfd8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805dfd8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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If you attach or paste a git patch, syzbot will apply it before testing.

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#syz undup

#syz test: https://github.com/ea1davis/linux bt/syz

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+0x32d/0x350 drivers/bluetooth/hci_vhci.c:336
Read of size 8 at addr ffff8880723fe000 by task syz.0.616/7968

CPU: 0 UID: 0 PID: 7968 Comm: syz.0.616 Not tainted 6.12.0-syzkaller-10299-g8e1aa2966d94 #0
force_devcd_write+0x32d/0x350 drivers/bluetooth/hci_vhci.c:336
RIP: 0033:0x7f5b6e785d29
RSP: 002b:00007f5b6f56d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5b6e975fa0 RCX: 00007f5b6e785d29
RBP: 00007f5b6e801aa8 R08: 0000000000000000 R09: 0000000000000000
R13: 0000000000000000 R14: 00007f5b6e975fa0 R15: 00007ffd5c295678
</TASK>

Allocated by task 6486:
vhci_open+0x4c/0x430 drivers/bluetooth/hci_vhci.c:639
Freed by task 6486:
slab_free_hook mm/slub.c:2338 [inline]
slab_free mm/slub.c:4598 [inline]
kfree+0x14f/0x4b0 mm/slub.c:4746
vhci_release+0xbb/0xf0 drivers/bluetooth/hci_vhci.c:675
do_exit+0xadd/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3016
The buggy address belongs to the object at ffff8880723fe000
freed 1024-byte region [ffff8880723fe000, ffff8880723fe400)
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x723f8
raw: 00fff00000000040 ffff88801ac41dc0 ffffea0001e8f600 dead000000000002
head: 00fff00000000040 ffff88801ac41dc0 ffffea0001e8f600 dead000000000002
head: 00fff00000000003 ffffea0001c8fe01 ffffffffffffffff 0000000000000000
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5899, tgid 5899 (syz-executor), ts 74750997698, free_ts 73623015670
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x2d1/0x350 mm/page_alloc.c:1556
prep_new_page mm/page_alloc.c:1564 [inline]
get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3474
__alloc_pages_noprof+0x223/0x25a0 mm/page_alloc.c:4751
alloc_pages_mpol_noprof+0x2c9/0x610 mm/mempolicy.c:2265
alloc_slab_page mm/slub.c:2408 [inline]
allocate_slab mm/slub.c:2574 [inline]
new_slab+0x2c9/0x410 mm/slub.c:2627
___slab_alloc+0xd1d/0x16e0 mm/slub.c:3815
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3905
__slab_alloc_node mm/slub.c:3980 [inline]
slab_alloc_node mm/slub.c:4141 [inline]
__kmalloc_cache_noprof+0xf6/0x420 mm/slub.c:4309
afs_alloc_call+0x4f/0x4a0 fs/afs/rxrpc.c:144
afs_charge_preallocation+0xff/0x330 fs/afs/rxrpc.c:736
afs_open_socket+0x298/0x350 fs/afs/rxrpc.c:95
afs_net_init+0x95d/0xc60 fs/afs/main.c:123
ops_init+0x1df/0x5f0 net/core/net_namespace.c:138
setup_net+0x21f/0x860 net/core/net_namespace.c:362
copy_net_ns+0x2b4/0x6b0 net/core/net_namespace.c:500
create_new_namespaces+0x3ea/0xad0 kernel/nsproxy.c:110
page last free pid 5853 tgid 5853 stack trace:
free_unref_page+0x661/0x1080 mm/page_alloc.c:2657
vfree+0x17a/0x890 mm/vmalloc.c:3382
kcov_put kernel/kcov.c:439 [inline]
kcov_put+0x2a/0x40 kernel/kcov.c:435
kcov_close+0xd/0x20 kernel/kcov.c:535
do_exit+0xadd/0x2d70 kernel/exit.c:938
do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
get_signal+0x2576/0x2610 kernel/signal.c:3016
ffff8880723fdf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880723fdf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880723fe000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880723fe080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880723fe100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit: 8e1aa296 Bluetooth: vhci: fix a uaf in force_devcd_write
git tree: https://github.com/ea1davis/linux bt/syz
console output: https://syzkaller.appspot.com/x/log.txt?x=171500b0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e8d97faf7b870c89
Note: no patches were applied.

For archival purposes, forwarding an incoming command email to
[email protected], [email protected].

***

Subject:
Author: [email protected]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: [email protected]
Tested-by: [email protected]

Tested on:

commit: 9b2ffa61 Merge tag 'mtd/fixes-for-6.13-rc5' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15749adf980000
kernel config: https://syzkaller.appspot.com/x/.config?x=c078001e66e4a17e
patch: https://syzkaller.appspot.com/x/patch.diff?x=174362f8580000

Note: testing is done by a robot and is best-effort only.