Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap_recv_frame

[syzbot <syzbot+5c915dc5dd417b83b348@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    e8784b0aef62 Merge tag 'usb-6.11-rc6' of git://git.kernel...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1600ea63980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b3e19fd08b312452
dashboard link: https://syzkaller.appspot.com/bug?extid=5c915dc5dd417b83b348
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13ba6d1f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10dfdadb980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e1d3f7f323a8/disk-e8784b0a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/01c01dcebf01/vmlinux-e8784b0a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/53cc8ab0ce4d/bzImage-e8784b0a.xz

Bisection is inconclusive: the first bad commit could be any of:

b79e04091010 Bluetooth: btintel: Fix null ptr deref in btintel_read_version
e7b02296fb40 Bluetooth: Remove BT_HS

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17d8bd73980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5c915dc5dd417b83b348@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in l2cap_conless_channel net/bluetooth/l2cap_core.c:6757 [inline]
BUG: KMSAN: uninit-value in l2cap_recv_frame+0xc9c5/0x18b10 net/bluetooth/l2cap_core.c:6831
 l2cap_conless_channel net/bluetooth/l2cap_core.c:6757 [inline]
 l2cap_recv_frame+0xc9c5/0x18b10 net/bluetooth/l2cap_core.c:6831
 l2cap_recv_acldata+0xdd9/0x2ac0 net/bluetooth/l2cap_core.c:7514
 hci_acldata_packet net/bluetooth/hci_core.c:3791 [inline]
 hci_rx_work+0xb38/0x1130 net/bluetooth/hci_core.c:4028
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xae0/0x1c40 kernel/workqueue.c:3312
 worker_thread+0xea7/0x14d0 kernel/workqueue.c:3389
 kthread+0x3e2/0x540 kernel/kthread.c:389
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:3994 [inline]
 slab_alloc_node mm/slub.c:4037 [inline]
 kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4080
 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:583
 __alloc_skb+0x363/0x7b0 net/core/skbuff.c:674
 alloc_skb include/linux/skbuff.h:1320 [inline]
 bt_skb_alloc include/net/bluetooth/bluetooth.h:493 [inline]
 vhci_get_user drivers/bluetooth/hci_vhci.c:487 [inline]
 vhci_write+0x128/0x910 drivers/bluetooth/hci_vhci.c:607
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xb2f/0x1550 fs/read_write.c:590
 ksys_write+0x20f/0x4c0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x93/0xe0 fs/read_write.c:652
 x64_sys_call+0x306a/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 5180 Comm: kworker/u9:2 Not tainted 6.11.0-rc5-syzkaller-00310-ge8784b0aef62 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: hci0 hci_rx_work
=====================================================


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