Hi Hillf, >> syzbot found the following crash on: >> >> HEAD commit: cee5a428 Add linux-next specific files for 20200203 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=167acbf1e00000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=ea1325a05ecd7b98 >> dashboard link: https://syzkaller.appspot.com/bug?extid=c3c5bdea7863886115dc >> compiler: gcc (GCC) 9.0.0 20181231 (experimental) >> >> Unfortunately, I don't have any reproducer for this crash yet. >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+c3c5bdea7863886115dc@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> can: request_module (can-proto-0) failed. >> can: request_module (can-proto-0) failed. >> can: request_module (can-proto-0) failed. >> ================================================================== >> BUG: KASAN: use-after-free in l2cap_sock_release+0x24c/0x290 net/bluetooth/l2cap_sock.c:1212 >> Read of size 8 at addr ffff8880944904a0 by task syz-fuzzer/9751 >> >> CPU: 0 PID: 9751 Comm: syz-fuzzer Not tainted 5.5.0-next-20200203-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+0x197/0x210 lib/dump_stack.c:118 >> print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 >> __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506 >> kasan_report+0x12/0x20 mm/kasan/common.c:641 >> __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135 >> l2cap_sock_release+0x24c/0x290 net/bluetooth/l2cap_sock.c:1212 >> __sock_release+0xce/0x280 net/socket.c:605 >> sock_close+0x1e/0x30 net/socket.c:1283 >> __fput+0x2ff/0x890 fs/file_table.c:280 >> ____fput+0x16/0x20 fs/file_table.c:313 >> task_work_run+0x145/0x1c0 kernel/task_work.c:113 >> tracehook_notify_resume include/linux/tracehook.h:188 [inline] >> exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164 >> prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] >> syscall_return_slowpath arch/x86/entry/common.c:278 [inline] >> do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> RIP: 0033:0x4afb40 >> Code: 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 49 c7 c2 00 00 00 00 49 c7 c0 00 00 00 00 49 c7 c1 00 00 00 00 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30 >> RSP: 002b:000000c00020b540 EFLAGS: 00000202 ORIG_RAX: 0000000000000003 >> RAX: 0000000000000000 RBX: 000000c00002e500 RCX: 00000000004afb40 >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 >> RBP: 000000c00020b580 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000202 R12: 00000000000000cc >> R13: 00000000000000cb R14: 0000000000000200 R15: 0000000000000200 >> >> Allocated by task 9751: >> save_stack+0x23/0x90 mm/kasan/common.c:72 >> set_track mm/kasan/common.c:80 [inline] >> __kasan_kmalloc mm/kasan/common.c:515 [inline] >> __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488 >> kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529 >> __do_kmalloc mm/slab.c:3656 [inline] >> __kmalloc+0x163/0x770 mm/slab.c:3665 >> kmalloc include/linux/slab.h:560 [inline] >> sk_prot_alloc+0x23a/0x310 net/core/sock.c:1603 >> sk_alloc+0x39/0xfd0 net/core/sock.c:1657 >> l2cap_sock_alloc.constprop.0+0x37/0x230 net/bluetooth/l2cap_sock.c:1603 >> l2cap_sock_create+0x11e/0x1c0 net/bluetooth/l2cap_sock.c:1649 >> bt_sock_create+0x16a/0x2d0 net/bluetooth/af_bluetooth.c:130 >> __sock_create+0x3ce/0x730 net/socket.c:1433 >> sock_create net/socket.c:1484 [inline] >> __sys_socket+0x103/0x220 net/socket.c:1526 >> __do_sys_socket net/socket.c:1535 [inline] >> __se_sys_socket net/socket.c:1533 [inline] >> __x64_sys_socket+0x73/0xb0 net/socket.c:1533 >> do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> Freed by task 9751: >> save_stack+0x23/0x90 mm/kasan/common.c:72 >> set_track mm/kasan/common.c:80 [inline] >> kasan_set_free_info mm/kasan/common.c:337 [inline] >> __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476 >> kasan_slab_free+0xe/0x10 mm/kasan/common.c:485 >> __cache_free mm/slab.c:3426 [inline] >> kfree+0x10a/0x2c0 mm/slab.c:3757 >> sk_prot_free net/core/sock.c:1640 [inline] >> __sk_destruct+0x5d8/0x7f0 net/core/sock.c:1724 >> sk_destruct+0xd5/0x110 net/core/sock.c:1739 >> __sk_free+0xfb/0x3f0 net/core/sock.c:1750 >> sk_free+0x83/0xb0 net/core/sock.c:1761 >> sock_put include/net/sock.h:1719 [inline] >> l2cap_sock_kill+0x160/0x190 net/bluetooth/l2cap_sock.c:1058 >> l2cap_sock_release+0x1c3/0x290 net/bluetooth/l2cap_sock.c:1210 >> __sock_release+0xce/0x280 net/socket.c:605 >> sock_close+0x1e/0x30 net/socket.c:1283 >> __fput+0x2ff/0x890 fs/file_table.c:280 >> ____fput+0x16/0x20 fs/file_table.c:313 >> task_work_run+0x145/0x1c0 kernel/task_work.c:113 >> tracehook_notify_resume include/linux/tracehook.h:188 [inline] >> exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164 >> prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] >> syscall_return_slowpath arch/x86/entry/common.c:278 [inline] >> do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> The buggy address belongs to the object at ffff888094490000 >> which belongs to the cache kmalloc-2k of size 2048 >> The buggy address is located 1184 bytes inside of >> 2048-byte region [ffff888094490000, ffff888094490800) >> The buggy address belongs to the page: >> page:ffffea0002512400 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0 >> flags: 0xfffe0000000200(slab) >> raw: 00fffe0000000200 ffffea00025123c8 ffffea00021bf608 ffff8880aa400e00 >> raw: 0000000000000000 ffff888094490000 0000000100000001 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff888094490380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff888094490400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> ffff888094490480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> ffff888094490500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff888094490580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== >> >> >> --- >> This bug is generated by a bot. It may contain errors. >> See https://goo.gl/tpsmEJ for more information about syzbot. >> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. >> >> syzbot will keep track of this bug report. See: >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > > Prefetch channel before killing sock. > > --- a/net/bluetooth/l2cap_sock.c > +++ b/net/bluetooth/l2cap_sock.c > @@ -1193,6 +1193,7 @@ static int l2cap_sock_release(struct soc > { > struct sock *sk = sock->sk; > int err; > + struct l2cap_chan *chan; > > BT_DBG("sock %p, sk %p", sock, sk); > > @@ -1202,15 +1203,16 @@ static int l2cap_sock_release(struct soc > bt_sock_unlink(&l2cap_sk_list, sk); > > err = l2cap_sock_shutdown(sock, 2); > + chan = l2cap_pi(sk)->chan; > > - l2cap_chan_hold(l2cap_pi(sk)->chan); > - l2cap_chan_lock(l2cap_pi(sk)->chan); > + l2cap_chan_hold(chan); > + l2cap_chan_lock(chan); > > sock_orphan(sk); > l2cap_sock_kill(sk); > > - l2cap_chan_unlock(l2cap_pi(sk)->chan); > - l2cap_chan_put(l2cap_pi(sk)->chan); > + l2cap_chan_unlock(chan); > + l2cap_chan_put(chan); > > return err; > } please send a proper patch with commit message and everything. That way I can easily apply it. Regards Marcel
