[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.490816] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 15.968777] random: sshd: uninitialized urandom read (32 bytes read) [ 16.360494] random: sshd: uninitialized urandom read (32 bytes read) [ 17.260577] random: sshd: uninitialized urandom read (32 bytes read) [ 17.392500] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.16' (ECDSA) to the list of known hosts. [ 22.912234] random: sshd: uninitialized urandom read (32 bytes read) 2018/07/12 08:44:55 parsed 1 programs [ 24.616900] random: cc1: uninitialized urandom read (8 bytes read) 2018/07/12 08:44:58 executed programs: 0 [ 25.879655] IPVS: Creating netns size=2536 id=1 [ 25.994661] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready [ 26.006048] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready [ 26.047667] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready [ 26.059742] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready [ 26.101398] IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready [ 26.112436] IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready [ 26.124247] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready [ 26.144978] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready [ 26.610927] IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready [ 26.635872] IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready [ 26.642140] IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready [ 26.649742] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready [ 30.018300] ================================================================== [ 30.025706] BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xed/0x110 [ 30.033050] Read of size 4 at addr ffff8801d55eca00 by task syz-executor0/4318 [ 30.040394] [ 30.042007] CPU: 0 PID: 4318 Comm: syz-executor0 Not tainted 4.9.112-g9e79039 #11 [ 30.049607] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 30.058965] ffff8801d4087c20 ffffffff81eb3249 ffffea0007557b00 ffff8801d55eca00 [ 30.067151] 0000000000000000 ffff8801d55eca00 ffffffff83013be0 ffff8801d4087c58 [ 30.075180] ffffffff81567bd9 ffff8801d55eca00 0000000000000004 0000000000000000 [ 30.083192] Call Trace: [ 30.085970] [] dump_stack+0xc1/0x128 [ 30.091329] [] ? sock_release+0x1c0/0x1c0 [ 30.097108] [] print_address_description+0x6c/0x234 [ 30.103750] [] ? sock_release+0x1c0/0x1c0 [ 30.109531] [] kasan_report.cold.6+0x242/0x2fe [ 30.115749] [] ? pppol2tp_session_destruct+0xed/0x110 [ 30.122577] [] __asan_report_load4_noabort+0x14/0x20 [ 30.129323] [] pppol2tp_session_destruct+0xed/0x110 [ 30.135964] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 30.142264] [] __sk_destruct+0x55/0x590 [ 30.147877] [] ? sock_release+0x1c0/0x1c0 [ 30.153661] [] sk_destruct+0x63/0x80 [ 30.159004] [] __sk_free+0x4f/0x220 [ 30.164371] [] sk_free+0x2b/0x40 [ 30.169367] [] pppol2tp_release+0x239/0x2e0 [ 30.175317] [] sock_release+0x96/0x1c0 [ 30.180838] [] sock_close+0x16/0x20 [ 30.186089] [] __fput+0x263/0x700 [ 30.191281] [] ____fput+0x15/0x20 [ 30.196544] [] task_work_run+0x10c/0x180 [ 30.202246] [] exit_to_usermode_loop+0xfc/0x120 [ 30.208553] [] do_fast_syscall_32+0x5c3/0x870 [ 30.214685] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 30.221328] [] entry_SYSENTER_compat+0x90/0xa2 [ 30.227619] [ 30.229227] Allocated by task 4318: [ 30.232830] save_stack_trace+0x16/0x20 [ 30.236781] save_stack+0x43/0xd0 [ 30.240207] kasan_kmalloc+0xc7/0xe0 [ 30.243897] __kmalloc+0x11d/0x300 [ 30.247414] l2tp_session_create+0x38/0x16f0 [ 30.251806] pppol2tp_connect+0x10d7/0x18f0 [ 30.256107] SYSC_connect+0x1b8/0x300 [ 30.260477] SyS_connect+0x24/0x30 [ 30.263993] do_fast_syscall_32+0x2f7/0x870 [ 30.268289] entry_SYSENTER_compat+0x90/0xa2 [ 30.272665] [ 30.274274] Freed by task 4316: [ 30.277535] save_stack_trace+0x16/0x20 [ 30.281480] save_stack+0x43/0xd0 [ 30.284907] kasan_slab_free+0x72/0xc0 [ 30.288775] kfree+0xfb/0x310 [ 30.291858] l2tp_session_free+0x166/0x200 [ 30.296082] l2tp_tunnel_closeall+0x284/0x350 [ 30.300554] l2tp_udp_encap_destroy+0x87/0xe0 [ 30.305024] udp_destroy_sock+0x118/0x1a0 [ 30.309156] sk_common_release+0x6d/0x300 [ 30.313282] udp_lib_close+0x15/0x20 [ 30.316982] inet_release+0xff/0x1d0 [ 30.320677] sock_release+0x96/0x1c0 [ 30.324374] sock_close+0x16/0x20 [ 30.327812] __fput+0x263/0x700 [ 30.331066] ____fput+0x15/0x20 [ 30.334337] task_work_run+0x10c/0x180 [ 30.338198] exit_to_usermode_loop+0xfc/0x120 [ 30.342667] do_fast_syscall_32+0x5c3/0x870 [ 30.346960] entry_SYSENTER_compat+0x90/0xa2 [ 30.351347] [ 30.352948] The buggy address belongs to the object at ffff8801d55eca00 [ 30.352948] which belongs to the cache kmalloc-512 of size 512 [ 30.365590] The buggy address is located 0 bytes inside of [ 30.365590] 512-byte region [ffff8801d55eca00, ffff8801d55ecc00) [ 30.377264] The buggy address belongs to the page: [ 30.382167] page:ffffea0007557b00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 30.392346] flags: 0x8000000000004080(slab|head) [ 30.397083] page dumped because: kasan: bad access detected [ 30.402763] [ 30.404360] Memory state around the buggy address: [ 30.409300] ffff8801d55ec900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 30.416650] ffff8801d55ec980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 30.424068] >ffff8801d55eca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 30.431395] ^ [ 30.434731] ffff8801d55eca80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 30.442062] ffff8801d55ecb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 30.449390] ================================================================== [ 30.456988] Disabling lock debugging due to kernel taint [ 30.462681] Kernel panic - not syncing: panic_on_warn set ... [ 30.462681] [ 30.470027] CPU: 0 PID: 4318 Comm: syz-executor0 Tainted: G B 4.9.112-g9e79039 #11 [ 30.478845] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 30.488179] ffff8801d4087b80 ffffffff81eb3249 ffffffff843c775f 00000000ffffffff [ 30.496210] 0000000000000000 0000000000000000 ffffffff83013be0 ffff8801d4087c40 [ 30.504212] ffffffff81421a55 0000000041b58ab3 ffffffff843bae78 ffffffff81421896 [ 30.512268] Call Trace: [ 30.514833] [] dump_stack+0xc1/0x128 [ 30.520177] [] ? sock_release+0x1c0/0x1c0 [ 30.525947] [] panic+0x1bf/0x3bc [ 30.530937] [] ? add_taint.cold.6+0x16/0x16 [ 30.536882] [] ? ___preempt_schedule+0x16/0x18 [ 30.543089] [] kasan_end_report+0x47/0x4f [ 30.548956] [] kasan_report.cold.6+0x76/0x2fe [ 30.555075] [] ? pppol2tp_session_destruct+0xed/0x110 [ 30.561888] [] __asan_report_load4_noabort+0x14/0x20 [ 30.568612] [] pppol2tp_session_destruct+0xed/0x110 [ 30.575248] [] ? pppol2tp_seq_start+0x4e0/0x4e0 [ 30.581539] [] __sk_destruct+0x55/0x590 [ 30.587137] [] ? sock_release+0x1c0/0x1c0 [ 30.592908] [] sk_destruct+0x63/0x80 [ 30.598445] [] __sk_free+0x4f/0x220 [ 30.603706] [] sk_free+0x2b/0x40 [ 30.608714] [] pppol2tp_release+0x239/0x2e0 [ 30.614782] [] sock_release+0x96/0x1c0 [ 30.620322] [] sock_close+0x16/0x20 [ 30.625580] [] __fput+0x263/0x700 [ 30.630657] [] ____fput+0x15/0x20 [ 30.635752] [] task_work_run+0x10c/0x180 [ 30.641460] [] exit_to_usermode_loop+0xfc/0x120 [ 30.647769] [] do_fast_syscall_32+0x5c3/0x870 [ 30.653899] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 30.660551] [] entry_SYSENTER_compat+0x90/0xa2 [ 30.667161] Dumping ftrace buffer: [ 30.670677] (ftrace buffer empty) [ 30.674364] Kernel Offset: disabled [ 30.677982] Rebooting in 86400 seconds..