linux-kernel - Re: [syzbot] [bluetooth?] KASAN: slab-out-of-bounds Read in hci_cmd_sync

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Message-ID: <6817fe1a.050a0220.11da1b.003d.GAE@google.com>
Date: Sun, 04 May 2025 16:54:02 -0700
From: syzbot <syzbot+5fe2d5bfbfbec0b675a0@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bluetooth?] KASAN: slab-out-of-bounds Read in hci_cmd_sync_alloc

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-out-of-bounds Read in hci_cmd_sync_alloc

==================================================================
BUG: KASAN: slab-out-of-bounds in skb_put_data include/linux/skbuff.h:2752 [inline]
BUG: KASAN: slab-out-of-bounds in hci_cmd_sync_alloc+0x300/0x3a0 net/bluetooth/hci_sync.c:67
Read of size 7 at addr ffff8881071ed206 by task kworker/u33:0/67

CPU: 0 UID: 0 PID: 67 Comm: kworker/u33:0 Not tainted 6.15.0-rc5-syzkaller-g92a09c47464d-dirty #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: hci0 hci_cmd_sync_work
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+0xe0/0x110 mm/kasan/report.c:634
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189
 __asan_memcpy+0x23/0x60 mm/kasan/shadow.c:105
 skb_put_data include/linux/skbuff.h:2752 [inline]
 hci_cmd_sync_alloc+0x300/0x3a0 net/bluetooth/hci_sync.c:67
 hci_cmd_sync_add net/bluetooth/hci_sync.c:99 [inline]
 __hci_cmd_sync_sk+0x157/0xc90 net/bluetooth/hci_sync.c:168
 __hci_cmd_sync_ev+0x3e/0x50 net/bluetooth/hci_sync.c:250
 send_hci_cmd_sync+0x152/0x3a0 net/bluetooth/mgmt.c:2540
 hci_cmd_sync_work+0x1a8/0x430 net/bluetooth/hci_sync.c:332
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6476:
 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:4327 [inline]
 __kmalloc_node_track_caller_noprof+0x221/0x510 mm/slub.c:4346
 kmemdup_noprof+0x29/0x60 mm/util.c:137
 kmemdup_noprof include/linux/fortify-string.h:765 [inline]
 mgmt_pending_new+0x10b/0x290 net/bluetooth/mgmt_util.c:259
 mgmt_hci_cmd_sync net/bluetooth/mgmt.c:2574 [inline]
 mgmt_hci_cmd_sync+0x58/0x1c0 net/bluetooth/mgmt.c:2562
 hci_mgmt_cmd net/bluetooth/hci_sock.c:1712 [inline]
 hci_sock_sendmsg+0x151f/0x25e0 net/bluetooth/hci_sock.c:1832
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg net/socket.c:727 [inline]
 sock_write_iter+0x4fc/0x5b0 net/socket.c:1131
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x5ba/0x1180 fs/read_write.c:684
 ksys_write+0x205/0x240 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8881071ed200
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 6 bytes inside of
 allocated 7-byte region [ffff8881071ed200, ffff8881071ed207)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1071ed
anon flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000000 ffff88801b442500 0000000000000000 dead000000000001
raw: 0000000000000000 0000000080800080 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 9516676162, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1718
 prep_new_page mm/page_alloc.c:1726 [inline]
 get_page_from_freelist+0x135c/0x3920 mm/page_alloc.c:3688
 __alloc_frozen_pages_noprof+0x263/0x23a0 mm/page_alloc.c:4970
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2450 [inline]
 allocate_slab mm/slub.c:2618 [inline]
 new_slab+0x244/0x340 mm/slub.c:2672
 ___slab_alloc+0xd9c/0x1940 mm/slub.c:3858
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3948
 __slab_alloc_node mm/slub.c:4023 [inline]
 slab_alloc_node mm/slub.c:4184 [inline]
 __do_kmalloc_node mm/slub.c:4326 [inline]
 __kmalloc_node_track_caller_noprof+0x2ee/0x510 mm/slub.c:4346
 kvasprintf+0xbc/0x160 lib/kasprintf.c:25
 kvasprintf_const+0x66/0x1a0 lib/kasprintf.c:49
 kobject_set_name_vargs+0x5a/0x140 lib/kobject.c:274
 kobject_add_varg lib/kobject.c:368 [inline]
 kobject_add+0x129/0x240 lib/kobject.c:426
 blk_mq_register_hctx+0x264/0x470 block/blk-mq-sysfs.c:172
 blk_mq_sysfs_register+0x208/0x5f0 block/blk-mq-sysfs.c:234
 blk_register_queue+0xe5/0x560 block/blk-sysfs.c:852
 add_disk_fwnode+0x911/0x13a0 block/genhd.c:505
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881071ed100: 07 fc fc fc 07 fc fc fc 07 fc fc fc 00 fc fc fc
 ffff8881071ed180: 00 fc fc fc 06 fc fc fc 00 fc fc fc 00 fc fc fc
>ffff8881071ed200: 07 fc fc fc fa fc fc fc 03 fc fc fc 03 fc fc fc
                   ^
 ffff8881071ed280: 03 fc fc fc 03 fc fc fc 03 fc fc fc 03 fc fc fc
 ffff8881071ed300: 05 fc fc fc 05 fc fc fc 05 fc fc fc 05 fc fc fc
==================================================================


Tested on:

commit:         92a09c47 Linux 6.15-rc5
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1524f0f4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b39cb28b0a399ed3
dashboard link: https://syzkaller.appspot.com/bug?extid=5fe2d5bfbfbec0b675a0
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=1239db68580000