[....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 19.202070] random: sshd: uninitialized urandom read (32 bytes read, 31 bits of entropy available) [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [ 19.900883] random: sshd: uninitialized urandom read (32 bytes read, 31 bits of entropy available) [ 20.168648] random: sshd: uninitialized urandom read (32 bytes read, 33 bits of entropy available) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.309419] random: sshd: uninitialized urandom read (32 bytes read, 125 bits of entropy available) [ 22.821631] random: nonblocking pool is initialized Warning: Permanently added '10.128.10.38' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 29.301394] ================================================================== [ 29.308809] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 29.316063] Read of size 4 at addr ffff8800b513c000 by task syz-executor934/3795 [ 29.323563] [ 29.325164] CPU: 0 PID: 3795 Comm: syz-executor934 Not tainted 4.4.132-g4f75c34 #43 [ 29.332926] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.342252] 0000000000000000 d50ca50e793c2493 ffff8801cd17fb50 ffffffff81e0df8d [ 29.350231] ffffea0002d44f00 ffff8800b513c000 0000000000000000 ffff8800b513c000 [ 29.358208] ffffffff82f18e30 ffff8801cd17fb88 ffffffff8151526c ffff8800b513c000 [ 29.366211] Call Trace: [ 29.368788] [] dump_stack+0xc1/0x124 [ 29.374147] [] ? sock_release+0x1c0/0x1c0 [ 29.379938] [] print_address_description+0x6c/0x216 [ 29.386610] [] ? sock_release+0x1c0/0x1c0 [ 29.386619] [] kasan_report.cold.7+0x175/0x2f7 [ 29.386628] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 29.386637] [] __asan_report_load4_noabort+0x14/0x20 [ 29.386647] [] l2tp_session_queue_purge+0xf4/0x100 [ 29.386654] [] ? sock_release+0x1c0/0x1c0 [ 29.386661] [] pppol2tp_release+0x1ff/0x310 [ 29.386667] [] sock_release+0x96/0x1c0 [ 29.386672] [] sock_close+0x16/0x20 [ 29.386683] [] __fput+0x235/0x6f0 [ 29.386688] [] ____fput+0x15/0x20 [ 29.386695] [] task_work_run+0x10f/0x190 [ 29.386702] [] do_exit+0x9e5/0x26b0 [ 29.386709] [] ? release_task.part.17+0x1200/0x1200 [ 29.386717] [] ? __do_page_fault+0x385/0xa10 [ 29.386726] [] ? retint_user+0x18/0x3c [ 29.386732] [] do_group_exit+0x111/0x330 [ 29.386739] [] ? trace_hardirqs_on_thunk+0x17/0x19 [ 29.386745] [] SyS_exit_group+0x1d/0x20 [ 29.386753] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 29.386755] [ 29.386759] Allocated by task 3793: [ 29.386770] [] save_stack_trace+0x26/0x50 [ 29.386777] [] save_stack+0x43/0xd0 [ 29.386784] [] kasan_kmalloc+0xc7/0xe0 [ 29.386791] [] __kmalloc+0x124/0x310 [ 29.386798] [] l2tp_session_create+0x39/0x1030 [ 29.386804] [] pppol2tp_connect+0x10f0/0x1910 [ 29.386811] [] SYSC_connect+0x1b8/0x300 [ 29.386819] [] SyS_connect+0x24/0x30 [ 29.386826] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 29.386828] [ 29.386830] Freed by task 3760: [ 29.386837] [] save_stack_trace+0x26/0x50 [ 29.386844] [] save_stack+0x43/0xd0 [ 29.386851] [] kasan_slab_free+0x72/0xc0 [ 29.386856] [] kfree+0xf4/0x310 [ 29.386863] [] l2tp_session_free+0x170/0x200 [ 29.386871] [] l2tp_tunnel_closeall+0x2b9/0x350 [ 29.386878] [] l2tp_udp_encap_destroy+0x8b/0xf0 [ 29.386886] [] udpv6_destroy_sock+0xb1/0xd0 [ 29.386893] [] sk_common_release+0x6d/0x300 [ 29.386900] [] udp_lib_close+0x15/0x20 [ 29.386908] [] inet_release+0xff/0x1d0 [ 29.386917] [] inet6_release+0x50/0x70 [ 29.386924] [] sock_release+0x96/0x1c0 [ 29.386930] [] sock_close+0x16/0x20 [ 29.386937] [] __fput+0x235/0x6f0 [ 29.386944] [] ____fput+0x15/0x20 [ 29.386955] [] task_work_run+0x10f/0x190 [ 29.386961] [] do_exit+0x9e5/0x26b0 [ 29.386968] [] do_group_exit+0x111/0x330 [ 29.386974] [] SyS_exit_group+0x1d/0x20 [ 29.386981] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 29.386982] [ 29.386987] The buggy address belongs to the object at ffff8800b513c000 [ 29.386987] which belongs to the cache kmalloc-512 of size 512 [ 29.386992] The buggy address is located 0 bytes inside of [ 29.386992] 512-byte region [ffff8800b513c000, ffff8800b513c200) [ 29.386993] The buggy address belongs to the page: [ 29.718467] ------------[ cut here ]------------ [ 29.723243] WARNING: CPU: 1 PID: 3814 at lib/list_debug.c:62 __list_del_entry+0x162/0x1c0() [ 29.731731] list_del corruption. next->prev should be ffff8801d60177b0, but was ffffffff8148c9a7 [ 29.740809] Kernel panic - not syncing: panic_on_warn set ... [ 29.740809] [ 29.748177] CPU: 1 PID: 3814 Comm: init Not tainted 4.4.132-g4f75c34 #43 [ 29.755025] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.764380] 0000000000000000 103fc28f219db8e3 ffff8801d6017510 ffffffff81e0df8d [ 29.772455] ffffffff83a43ec0 ffff8801d601e000 ffffffff83c134c0 0000000000000009 [ 29.780531] 000000000000003e ffff8801d60175d0 ffffffff81409de4 0000000041b58ab3 [ 29.788614] Call Trace: [ 29.791197] [] dump_stack+0xc1/0x124 [ 29.796565] [] panic+0x19e/0x38d [ 29.801589] [] ? add_taint.cold.4+0x16/0x16 [ 29.807566] [] ? warn_slowpath_common.cold.6+0x5/0x20 [ 29.814415] [] warn_slowpath_common.cold.6+0x20/0x20 [ 29.821184] [] ? __list_del_entry+0x162/0x1c0 [ 29.827338] [] warn_slowpath_fmt+0xbf/0x100 [ 29.833319] [] ? warn_slowpath_common+0x120/0x120 [ 29.839824] [] ? dump_page_badflags+0x57/0x70 [ 29.845982] [] __list_del_entry+0x162/0x1c0 [ 29.851966] [] mutex_remove_waiter+0x21e/0x3c0 [ 29.858208] [] mutex_lock_nested+0x4a0/0x850 [ 29.864270] [] ? tty_open+0x53e/0xf00 [ 29.869732] [] ? mutex_lock_killable_nested+0x980/0x980 [ 29.876754] [] ? tty_open+0x158/0xf00 [ 29.882209] [] ? kmem_cache_alloc_trace+0x104/0x2c0 [ 29.888880] [] ? tty_open+0x158/0xf00 [ 29.894345] [] tty_open+0x53e/0xf00 [ 29.899631] [] ? tty_init_dev+0x430/0x430 [ 29.905443] [] ? chrdev_open+0xc7/0x4c0 [ 29.911078] [] ? tty_init_dev+0x430/0x430 [ 29.916884] [] chrdev_open+0x22d/0x4c0 [ 29.922433] [] ? cdev_put.part.0+0x50/0x50 [ 29.928329] [] do_dentry_open+0x68b/0xbc0 [ 29.934137] [] ? __inode_permission2+0x9b/0x240 [ 29.940459] [] ? cdev_put.part.0+0x50/0x50 [ 29.946358] [] vfs_open+0x12a/0x210 [ 29.951649] [] ? may_open.isra.40+0x156/0x240 [ 29.957807] [] path_openat+0x4ee/0x3a10 [ 29.963442] [] ? depot_save_stack+0x1c9/0x610 [ 29.969600] [] ? path_lookupat.isra.36+0x410/0x410 [ 29.976186] [] ? getname_flags+0xc7/0x580 [ 29.981994] [] ? getname+0x19/0x20 [ 29.987196] [] ? do_sys_open+0x203/0x610 [ 29.992916] [] ? SyS_open+0x2d/0x40 [ 29.998207] [] ? entry_SYSCALL_64_fastpath+0x22/0x9e [ 30.004971] [] ? debug_check_no_locks_freed+0x210/0x210 [ 30.011994] [] ? __lock_is_held+0xa2/0xf0 [ 30.017803] [] do_filp_open+0x197/0x270 [ 30.023443] [] ? user_path_mountpoint_at+0x70/0x70 [ 30.030029] [] ? _raw_spin_unlock+0x2c/0x50 [ 30.036012] [] ? __alloc_fd+0x1f3/0x4a0 [ 30.041645] [] do_sys_open+0x31c/0x610 [ 30.047186] [] ? filp_open+0x70/0x70 [ 30.052560] [] ? proc_clear_tty+0xd9/0x140 [ 30.058451] [] ? _raw_write_unlock_irq+0x27/0x50 [ 30.064865] [] SyS_open+0x2d/0x40 [ 30.069976] [] entry_SYSCALL_64_fastpath+0x22/0x9e [ 31.059066] PANIC: double fault, error_code: 0x0 [ 31.063850] CPU: 0 PID: 3795 Comm: syz-executor934 Not tainted 4.4.132-g4f75c34 #43 [ 31.071617] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 31.080949] task: ffff8800b16fe000 task.stack: ffff8801cd178000 [ 31.086978] RIP: 0010:[] [] dump_page_badflags+0x1a/0x70 [ 31.095746] RSP: 0018:ffff880100000000 EFLAGS: 00010086 [ 31.101170] RAX: ffff8800b16fe000 RBX: ffffea0002d44f00 RCX: 0000000000000000 [ 31.108419] RDX: 0000000000000000 RSI: ffffffff83aa9be0 RDI: ffffea0002d44f00 [ 31.115666] RBP: ffff880100000030 R08: 0000000000000001 R09: 0000000000000000 [ 31.122914] R10: 0000000000000001 R11: ffffffff858f74a7 R12: 0000000000000000 [ 31.130160] R13: ffffffff83aa9be0 R14: ffff8800b513c000 R15: ffff8800b513c200 [ 31.137409] FS: 00007f18b0e54700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 [ 31.145613] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 31.151469] CR2: ffff8800fffffff8 CR3: 00000000b1931000 CR4: 00000000001606f0 [ 31.158719] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 31.165971] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 31.173216] Stack: [ 31.175338] [ 31.176941] Call Trace: [ 31.179501] [ 31.181544] Code: df e8 2b c7 06 00 eb dd 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 49 89 f5 41 54 49 89 d4 53 48 89 fb 48 83 ec 08 71 48 ec ff 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea [ 31.218451] Shutting down cpus with NMI [ 31.222916] Dumping ftrace buffer: [ 31.226528] (ftrace buffer empty) [ 31.230209] Kernel Offset: disabled [ 31.233823] Rebooting in 86400 seconds..