[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 16.404153] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 19.024308] random: sshd: uninitialized urandom read (32 bytes read) [ 19.524326] random: sshd: uninitialized urandom read (32 bytes read) [ 20.429507] random: sshd: uninitialized urandom read (32 bytes read) [ 20.559933] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.27' (ECDSA) to the list of known hosts. [ 25.943779] random: sshd: uninitialized urandom read (32 bytes read) 2018/07/16 10:44:31 parsed 1 programs [ 27.498349] random: cc1: uninitialized urandom read (8 bytes read) 2018/07/16 10:44:34 executed programs: 0 [ 28.999953] IPVS: Creating netns size=2536 id=1 [ 29.252503] ================================================================== [ 29.259910] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 29.267173] Read of size 4 at addr ffff8801c6e91400 by task syz-executor0/3843 [ 29.274512] [ 29.276130] CPU: 1 PID: 3843 Comm: syz-executor0 Not tainted 4.9.112-g9e79039 #11 [ 29.283843] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.293174] ffff8801d8b1fca0 ffffffff81eb3249 ffffea00071ba400 ffff8801c6e91400 [ 29.301177] 0000000000000000 ffff8801c6e91400 ffffffff83013be0 ffff8801d8b1fcd8 [ 29.310043] ffffffff81567bd9 ffff8801c6e91400 0000000000000004 0000000000000000 [ 29.318077] Call Trace: [ 29.320648] [] dump_stack+0xc1/0x128 [ 29.326006] [] ? sock_release+0x1c0/0x1c0 [ 29.331794] [] print_address_description+0x6c/0x234 [ 29.338445] [] ? sock_release+0x1c0/0x1c0 [ 29.344225] [] kasan_report.cold.6+0x242/0x2fe [ 29.350447] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 29.357193] [] __asan_report_load4_noabort+0x14/0x20 [ 29.363923] [] l2tp_session_queue_purge+0xf4/0x100 [ 29.370492] [] ? sock_release+0x1c0/0x1c0 [ 29.376263] [] pppol2tp_release+0x1fb/0x2e0 [ 29.382218] [] sock_release+0x96/0x1c0 [ 29.387728] [] sock_close+0x16/0x20 [ 29.392977] [] __fput+0x263/0x700 [ 29.398052] [] ____fput+0x15/0x20 [ 29.403130] [] task_work_run+0x10c/0x180 [ 29.412810] [] exit_to_usermode_loop+0xfc/0x120 [ 29.419100] [] do_fast_syscall_32+0x5c3/0x870 [ 29.425218] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 29.431857] [] entry_SYSENTER_compat+0x90/0xa2 [ 29.438061] [ 29.439663] Allocated by task 3843: [ 29.443276] save_stack_trace+0x16/0x20 [ 29.447233] save_stack+0x43/0xd0 [ 29.450660] kasan_kmalloc+0xc7/0xe0 [ 29.454349] __kmalloc+0x11d/0x300 [ 29.457865] l2tp_session_create+0x38/0x16f0 [ 29.462247] pppol2tp_connect+0x10d7/0x18f0 [ 29.466545] SYSC_connect+0x1b8/0x300 [ 29.470316] SyS_connect+0x24/0x30 [ 29.473827] do_fast_syscall_32+0x2f7/0x870 [ 29.478121] entry_SYSENTER_compat+0x90/0xa2 [ 29.482500] [ 29.484098] Freed by task 3842: [ 29.487352] save_stack_trace+0x16/0x20 [ 29.491301] save_stack+0x43/0xd0 [ 29.494726] kasan_slab_free+0x72/0xc0 [ 29.498587] kfree+0xfb/0x310 [ 29.501668] l2tp_session_free+0x166/0x200 [ 29.505876] l2tp_tunnel_closeall+0x284/0x350 [ 29.510346] l2tp_udp_encap_destroy+0x87/0xe0 [ 29.514819] udpv6_destroy_sock+0xb1/0xd0 [ 29.518941] sk_common_release+0x6d/0x300 [ 29.523062] udp_lib_close+0x15/0x20 [ 29.526750] inet_release+0xff/0x1d0 [ 29.530446] inet6_release+0x50/0x70 [ 29.534135] sock_release+0x96/0x1c0 [ 29.537820] sock_close+0x16/0x20 [ 29.541254] __fput+0x263/0x700 [ 29.544505] ____fput+0x15/0x20 [ 29.547759] task_work_run+0x10c/0x180 [ 29.551620] exit_to_usermode_loop+0xfc/0x120 [ 29.556086] do_fast_syscall_32+0x5c3/0x870 [ 29.560401] entry_SYSENTER_compat+0x90/0xa2 [ 29.564781] [ 29.566383] The buggy address belongs to the object at ffff8801c6e91400 [ 29.566383] which belongs to the cache kmalloc-512 of size 512 [ 29.579016] The buggy address is located 0 bytes inside of [ 29.579016] 512-byte region [ffff8801c6e91400, ffff8801c6e91600) [ 29.590687] The buggy address belongs to the page: [ 29.595590] page:ffffea00071ba400 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 29.605792] flags: 0x8000000000004080(slab|head) [ 29.610519] page dumped because: kasan: bad access detected [ 29.616197] [ 29.617793] Memory state around the buggy address: [ 29.622693] ffff8801c6e91300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 29.630024] ffff8801c6e91380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 29.637366] >ffff8801c6e91400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 29.644697] ^ [ 29.648037] ffff8801c6e91480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 29.655371] ffff8801c6e91500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 29.662709] ================================================================== [ 29.670041] Disabling lock debugging due to kernel taint [ 29.675773] Kernel panic - not syncing: panic_on_warn set ... [ 29.675773] [ 29.683133] CPU: 1 PID: 3843 Comm: syz-executor0 Tainted: G B 4.9.112-g9e79039 #11 [ 29.691942] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 29.701269] ffff8801d8b1fc00 ffffffff81eb3249 ffffffff843c775f 00000000ffffffff [ 29.709255] 0000000000000000 0000000000000001 ffffffff83013be0 ffff8801d8b1fcc0 [ 29.717264] ffffffff81421a55 0000000041b58ab3 ffffffff843bae78 ffffffff81421896 [ 29.725270] Call Trace: [ 29.727838] [] dump_stack+0xc1/0x128 [ 29.733178] [] ? sock_release+0x1c0/0x1c0 [ 29.738950] [] panic+0x1bf/0x3bc [ 29.743938] [] ? add_taint.cold.6+0x16/0x16 [ 29.749889] [] ? ___preempt_schedule+0x16/0x18 [ 29.756109] [] kasan_end_report+0x47/0x4f [ 29.761882] [] kasan_report.cold.6+0x76/0x2fe [ 29.768008] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 29.774737] [] __asan_report_load4_noabort+0x14/0x20 [ 29.781466] [] l2tp_session_queue_purge+0xf4/0x100 [ 29.788021] [] ? sock_release+0x1c0/0x1c0 [ 29.793804] [] pppol2tp_release+0x1fb/0x2e0 [ 29.799751] [] sock_release+0x96/0x1c0 [ 29.805263] [] sock_close+0x16/0x20 [ 29.810513] [] __fput+0x263/0x700 [ 29.815590] [] ____fput+0x15/0x20 [ 29.820672] [] task_work_run+0x10c/0x180 [ 29.826356] [] exit_to_usermode_loop+0xfc/0x120 [ 29.832646] [] do_fast_syscall_32+0x5c3/0x870 [ 29.838765] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 29.845409] [] entry_SYSENTER_compat+0x90/0xa2 [ 29.852124] Dumping ftrace buffer: [ 29.855650] (ftrace buffer empty) [ 29.859345] Kernel Offset: disabled [ 29.862948] Rebooting in 86400 seconds..