On Sun, Jun 06, 2021 at 04:50:04PM +0800, Hillf Danton wrote: > On 2020-08-02 20:45 > > syzbot found the following issue on: > > > > HEAD commit: ac3a0c84 Merge git://git.kernel.org/pub/scm/linux/kernel/g.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=11b8d570900000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=e59ee776d5aa8d55 > > dashboard link: https://syzkaller.appspot.com/bug?extid=305a91e025a73e4fd6ce > > compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f7ceea900000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17e5de04900000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+305a91e025a73e4fd6ce@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > IPVS: ftp: loaded support on port[0] = 21 > > ================================================================== > > BUG: KASAN: use-after-free in hci_chan_del+0x33/0x130 net/bluetooth/hci_conn.c:1707 > > Read of size 8 at addr ffff8880a9591f18 by task syz-executor081/6793 > > > > CPU: 0 PID: 6793 Comm: syz-executor081 Not tainted 5.8.0-rc7-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x1f0/0x31e lib/dump_stack.c:118 > > print_address_description+0x66/0x5a0 mm/kasan/report.c:383 > > __kasan_report mm/kasan/report.c:513 [inline] > > kasan_report+0x132/0x1d0 mm/kasan/report.c:530 > > hci_chan_del+0x33/0x130 net/bluetooth/hci_conn.c:1707 > > l2cap_conn_del+0x4c2/0x650 net/bluetooth/l2cap_core.c:1900 > > hci_disconn_cfm include/net/bluetooth/hci_core.h:1355 [inline] > > hci_conn_hash_flush+0x127/0x200 net/bluetooth/hci_conn.c:1536 > > hci_dev_do_close+0xb7b/0x1040 net/bluetooth/hci_core.c:1761 > > hci_unregister_dev+0x16d/0x1590 net/bluetooth/hci_core.c:3606 > > vhci_release+0x73/0xc0 drivers/bluetooth/hci_vhci.c:340 > > __fput+0x2f0/0x750 fs/file_table.c:281 > > task_work_run+0x137/0x1c0 kernel/task_work.c:135 > > exit_task_work include/linux/task_work.h:25 [inline] > > do_exit+0x601/0x1f80 kernel/exit.c:805 > > do_group_exit+0x161/0x2d0 kernel/exit.c:903 > > __do_sys_exit_group+0x13/0x20 kernel/exit.c:914 > > __se_sys_exit_group+0x10/0x10 kernel/exit.c:912 > > __x64_sys_exit_group+0x37/0x40 kernel/exit.c:912 > > do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > To fix the uaf reported, add reference count to hci channel to track users. > Then only channels with zero users will be released. > > It is now only for thoughts. > > +++ x/include/net/bluetooth/hci_core.h > @@ -704,6 +704,7 @@ struct hci_chan { > struct sk_buff_head data_q; > unsigned int sent; > __u8 state; > + atomic_t ref; Please no, never use "raw" atomic variables. Especially for something like this, use a kref. thanks, greg k-h
