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BUG: KASAN: slab-use-after-free in force_devcd_write+0x317/0x330 drivers/bluetooth/hci_vhci.c:327
Read of size 8 at addr ffff88814e392000 by task syz.2.866/10009

CPU: 0 UID: 0 PID: 10009 Comm: syz.2.866 Tainted: G     U             6.14.0-syzkaller #0
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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+0xc3/0x670 mm/kasan/report.c:521
 kasan_report+0xd9/0x110 mm/kasan/report.c:634
 force_devcd_write+0x317/0x330 drivers/bluetooth/hci_vhci.c:327
 full_proxy_write+0x13c/0x200 fs/debugfs/file.c:398
 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: 0033:0x7f2ba298d169
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:00007f2ba38a1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2ba2ba6080 RCX: 00007f2ba298d169
RDX: 000000000000000e RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00007f2ba2a0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f2ba2ba6080 R15: 00007ffc566b7838
 </TASK>

Allocated by task 9261:
 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
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4294 [inline]
 __kmalloc_node_track_caller_noprof+0x222/0x510 mm/slub.c:4313
 kmalloc_reserve+0xef/0x2c0 net/core/skbuff.c:537
 pskb_expand_head+0x237/0x1050 net/core/skbuff.c:2185
 __skb_cow include/linux/skbuff.h:3769 [inline]
 skb_cow_head include/linux/skbuff.h:3803 [inline]
 l2tp_xmit_core net/l2tp/l2tp_core.c:1238 [inline]
 l2tp_xmit_skb+0x246/0x1930 net/l2tp/l2tp_core.c:1325
 pppol2tp_sendmsg+0x47b/0x5e0 net/l2tp/l2tp_ppp.c:313
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:733 [inline]
 ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2573
 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2627
 __sys_sendmmsg+0x201/0x420 net/socket.c:2716
 __do_sys_sendmmsg net/socket.c:2743 [inline]
 __se_sys_sendmmsg net/socket.c:2740 [inline]
 __x64_sys_sendmmsg+0x9c/0x100 net/socket.c:2740
 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 9261:
 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:2353 [inline]
 slab_free mm/slub.c:4609 [inline]
 kfree+0x2c4/0x4d0 mm/slub.c:4757
 skb_kfree_head net/core/skbuff.c:996 [inline]
 skb_free_head+0x108/0x1d0 net/core/skbuff.c:1008
 skb_release_data+0x560/0x730 net/core/skbuff.c:1035
 skb_release_all net/core/skbuff.c:1100 [inline]
 __kfree_skb net/core/skbuff.c:1114 [inline]
 sk_skb_reason_drop+0x129/0x1a0 net/core/skbuff.c:1152
 kfree_skb_reason include/linux/skbuff.h:1271 [inline]
 kfree_skb include/linux/skbuff.h:1280 [inline]
 l2tp_xmit_core net/l2tp/l2tp_core.c:1271 [inline]
 l2tp_xmit_skb+0xdcb/0x1930 net/l2tp/l2tp_core.c:1325
 pppol2tp_sendmsg+0x47b/0x5e0 net/l2tp/l2tp_ppp.c:313
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:733 [inline]
 ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2573
 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2627
 __sys_sendmmsg+0x201/0x420 net/socket.c:2716
 __do_sys_sendmmsg net/socket.c:2743 [inline]
 __se_sys_sendmmsg net/socket.c:2740 [inline]
 __x64_sys_sendmmsg+0x9c/0x100 net/socket.c:2740
 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

The buggy address belongs to the object at ffff88814e392000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 0 bytes inside of
 freed 1024-byte region [ffff88814e392000, ffff88814e392400)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88814e392000 pfn:0x14e390
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000240(workingset|head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000240 ffff88801b041dc0 ffffea000513b810 ffffea0005382810
raw: ffff88814e392000 000000000010000c 00000000f5000000 0000000000000000
head: 057ff00000000240 ffff88801b041dc0 ffffea000513b810 ffffea0005382810
head: ffff88814e392000 000000000010000c 00000000f5000000 0000000000000000
head: 057ff00000000003 ffffea000538e401 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 1, tgid 1 (swapper/0), ts 29300886327, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x221/0x2470 mm/page_alloc.c:4740
 alloc_pages_mpol+0x1fc/0x540 mm/mempolicy.c:2270
 alloc_slab_page mm/slub.c:2423 [inline]
 allocate_slab mm/slub.c:2587 [inline]
 new_slab+0x23d/0x330 mm/slub.c:2640
 ___slab_alloc+0xc5d/0x1720 mm/slub.c:3826
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3916
 __slab_alloc_node mm/slub.c:3991 [inline]
 slab_alloc_node mm/slub.c:4152 [inline]
 __do_kmalloc_node mm/slub.c:4293 [inline]
 __kmalloc_node_track_caller_noprof+0x2f1/0x510 mm/slub.c:4313
 __do_krealloc mm/slub.c:4820 [inline]
 krealloc_noprof+0x157/0x380 mm/slub.c:4873
 add_sysfs_param+0xcb/0x960 kernel/params.c:654
 kernel_add_sysfs_param kernel/params.c:817 [inline]
 param_sysfs_builtin kernel/params.c:856 [inline]
 param_sysfs_builtin_init+0x2ce/0x460 kernel/params.c:990
 do_one_initcall+0x128/0x700 init/main.c:1257
 do_initcall_level init/main.c:1319 [inline]
 do_initcalls init/main.c:1335 [inline]
 do_basic_setup init/main.c:1354 [inline]
 kernel_init_freeable+0x5c7/0x900 init/main.c:1568
 kernel_init+0x1c/0x2b0 init/main.c:1457
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88814e391f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88814e391f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88814e392000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88814e392080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88814e392100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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