On Tue, Jul 31, 2018 at 5:43 PM, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: > On Mon, Jul 30, 2018 at 11:15:03AM -0700, syzbot wrote: >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: acb1872577b3 Linux 4.18-rc7 >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=14eb932c400000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=2dc0cd7c2eefb46f >> dashboard link: https://syzkaller.appspot.com/bug?extid=bd391451452fb0b93039 >> compiler: gcc (GCC) 8.0.1 20180413 (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+bd391451452fb0b93039@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> netlink: 'syz-executor5': attribute type 2 has an invalid length. >> binder: 28577:28588 transaction failed 29189/-22, size 0-0 line 2852 >> ================================================================== >> BUG: KASAN: use-after-free in debug_spin_lock_before >> kernel/locking/spinlock_debug.c:83 [inline] >> BUG: KASAN: use-after-free in do_raw_spin_lock+0x1c0/0x200 >> kernel/locking/spinlock_debug.c:112 >> Read of size 4 at addr ffff880194d0ec6c by task syz-executor4/28583 >> >> CPU: 1 PID: 28583 Comm: syz-executor4 Not tainted 4.18.0-rc7+ #169 >> 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+0x1c9/0x2b4 lib/dump_stack.c:113 >> print_address_description+0x6c/0x20b mm/kasan/report.c:256 >> kasan_report_error mm/kasan/report.c:354 [inline] >> kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412 >> __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 >> debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline] >> do_raw_spin_lock+0x1c0/0x200 kernel/locking/spinlock_debug.c:112 >> __raw_spin_lock_bh include/linux/spinlock_api_smp.h:136 [inline] >> _raw_spin_lock_bh+0x39/0x40 kernel/locking/spinlock.c:168 >> spin_lock_bh include/linux/spinlock.h:315 [inline] >> vhost_transport_send_pkt+0x12e/0x380 drivers/vhost/vsock.c:223 > > Thanks for the vsock fuzzing. This is a useful bug report. Thanks. But note that syzkaller descriptions for vsock were written by people who have no idea what is vsock whatsoever: https://github.com/google/syzkaller/blob/master/sys/linux/socket_vnet.txt So most likely fuzzing is inefficient and does not test the most interesting parts of vsock. > It looks like vhost_vsock_get() needs to involve a reference count so > that vhost_vsock instances cannot be freed while something is still > using them. > > The reproducer probably involves racing close() with connect(). > > I am looking into a fix. > > Stefan > >> virtio_transport_send_pkt_info+0x31d/0x460 >> net/vmw_vsock/virtio_transport_common.c:190 >> virtio_transport_connect+0x17c/0x220 >> net/vmw_vsock/virtio_transport_common.c:588 >> vsock_stream_connect+0x4fb/0xfc0 net/vmw_vsock/af_vsock.c:1197 >> __sys_connect+0x37d/0x4c0 net/socket.c:1673 >> __do_sys_connect net/socket.c:1684 [inline] >> __se_sys_connect net/socket.c:1681 [inline] >> __x64_sys_connect+0x73/0xb0 net/socket.c:1681 >> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> RIP: 0033:0x456a09 >> Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 >> 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 >> RSP: 002b:00007fa4aee5bc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a >> RAX: ffffffffffffffda RBX: 00007fa4aee5c6d4 RCX: 0000000000456a09 >> RDX: 0000000000000010 RSI: 0000000020000200 RDI: 0000000000000016 >> RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff >> R13: 00000000004ca838 R14: 00000000004c25fb R15: 0000000000000000 >> >> Allocated by task 28583: >> save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >> set_track mm/kasan/kasan.c:460 [inline] >> kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 >> __do_kmalloc_node mm/slab.c:3682 [inline] >> __kmalloc_node+0x47/0x70 mm/slab.c:3689 >> kmalloc_node include/linux/slab.h:555 [inline] >> kvmalloc_node+0xb9/0xf0 mm/util.c:423 >> kvmalloc include/linux/mm.h:573 [inline] >> vhost_vsock_dev_open+0xa2/0x5a0 drivers/vhost/vsock.c:511 >> misc_open+0x3ca/0x560 drivers/char/misc.c:141 >> chrdev_open+0x25a/0x770 fs/char_dev.c:417 >> do_dentry_open+0x818/0xe40 fs/open.c:794 >> vfs_open+0x139/0x230 fs/open.c:908 >> do_last fs/namei.c:3399 [inline] >> path_openat+0x174a/0x4e10 fs/namei.c:3540 >> do_filp_open+0x255/0x380 fs/namei.c:3574 >> do_sys_open+0x584/0x760 fs/open.c:1101 >> __do_sys_openat fs/open.c:1128 [inline] >> __se_sys_openat fs/open.c:1122 [inline] >> __x64_sys_openat+0x9d/0x100 fs/open.c:1122 >> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> Freed by task 28579: >> save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >> set_track mm/kasan/kasan.c:460 [inline] >> __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 >> kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 >> __cache_free mm/slab.c:3498 [inline] >> kfree+0xd9/0x260 mm/slab.c:3813 >> kvfree+0x61/0x70 mm/util.c:442 >> vhost_vsock_free drivers/vhost/vsock.c:499 [inline] >> vhost_vsock_dev_release+0x4fd/0x750 drivers/vhost/vsock.c:604 >> __fput+0x355/0x8b0 fs/file_table.c:209 >> ____fput+0x15/0x20 fs/file_table.c:243 >> task_work_run+0x1ec/0x2a0 kernel/task_work.c:113 >> tracehook_notify_resume include/linux/tracehook.h:192 [inline] >> exit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166 >> prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] >> syscall_return_slowpath arch/x86/entry/common.c:268 [inline] >> do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> >> The buggy address belongs to the object at ffff880194d05f80 >> which belongs to the cache kmalloc-65536 of size 65536 >> The buggy address is located 36076 bytes inside of >> 65536-byte region [ffff880194d05f80, ffff880194d15f80) >> The buggy address belongs to the page: >> page:ffffea0006534000 count:1 mapcount:0 mapping:ffff8801dac02500 index:0x0 >> compound_mapcount: 0 >> flags: 0x2fffc0000008100(slab|head) >> raw: 02fffc0000008100 ffffea0006599808 ffff8801dac01e48 ffff8801dac02500 >> raw: 0000000000000000 ffff880194d05f80 0000000100000001 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff880194d0eb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff880194d0eb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> > ffff880194d0ec00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ^ >> ffff880194d0ec80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff880194d0ed00: 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#bug-status-tracking for how to communicate with >> syzbot. > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20180731154351.GF17816%40stefanha-x1.localdomain. > For more options, visit https://groups.google.com/d/optout.
