[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.637585] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. [ 13.888009] random: sshd: uninitialized urandom read (32 bytes read) [ 14.192918] random: sshd: uninitialized urandom read (32 bytes read) Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 15.405667] random: sshd: uninitialized urandom read (32 bytes read) [ 94.457348] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.0.27' (ECDSA) to the list of known hosts. [ 99.947164] random: sshd: uninitialized urandom read (32 bytes read) 2018/06/17 11:16:32 parsed 1 programs [ 101.401142] random: cc1: uninitialized urandom read (8 bytes read) 2018/06/17 11:16:34 executed programs: 0 [ 102.369118] IPVS: Creating netns size=2536 id=1 [ 102.482460] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready [ 102.494690] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready [ 102.529520] IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready [ 102.541349] IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready [ 102.575879] IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready [ 102.588323] IPv6: ADDRCONF(NETDEV_UP): veth1_to_team: link is not ready [ 102.600414] IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready [ 102.614064] IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready [ 102.909664] IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready [ 102.936509] IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready [ 102.942663] IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready [ 102.950361] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready [ 103.263782] ================================================================== [ 103.271168] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 103.278419] Read of size 4 at addr ffff8801be4f2c80 by task syz-executor0/4123 [ 103.285751] [ 103.287357] CPU: 1 PID: 4123 Comm: syz-executor0 Not tainted 4.9.109-ga4230be #2 [ 103.294863] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 103.304193] ffff8801b7b0fca0 ffffffff81eb3e29 ffffea0006f93c80 ffff8801be4f2c80 [ 103.312198] 0000000000000000 ffff8801be4f2c80 ffffffff83013be0 ffff8801b7b0fcd8 [ 103.320220] ffffffff81567a89 ffff8801be4f2c80 0000000000000004 0000000000000000 [ 103.328211] Call Trace: [ 103.330776] [] dump_stack+0xc1/0x128 [ 103.336116] [] ? sock_release+0x1c0/0x1c0 [ 103.341890] [] print_address_description+0x6c/0x234 [ 103.348548] [] ? sock_release+0x1c0/0x1c0 [ 103.354326] [] kasan_report.cold.6+0x242/0x2fe [ 103.360533] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 103.367268] [] __asan_report_load4_noabort+0x14/0x20 [ 103.374007] [] l2tp_session_queue_purge+0xf4/0x100 [ 103.380568] [] ? sock_release+0x1c0/0x1c0 [ 103.386351] [] pppol2tp_release+0x1fb/0x2e0 [ 103.392306] [] sock_release+0x96/0x1c0 [ 103.397819] [] sock_close+0x16/0x20 [ 103.403070] [] __fput+0x263/0x700 [ 103.408149] [] ____fput+0x15/0x20 [ 103.413234] [] task_work_run+0x10c/0x180 [ 103.418930] [] exit_to_usermode_loop+0xfc/0x120 [ 103.425222] [] do_fast_syscall_32+0x5c3/0x870 [ 103.431343] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 103.437984] [] entry_SYSENTER_compat+0x90/0xa2 [ 103.444197] [ 103.445798] Allocated by task 4123: [ 103.449401] save_stack_trace+0x16/0x20 [ 103.453345] save_stack+0x43/0xd0 [ 103.456771] kasan_kmalloc+0xc7/0xe0 [ 103.460488] __kmalloc+0x11d/0x300 [ 103.464013] l2tp_session_create+0x38/0x16f0 [ 103.468408] pppol2tp_connect+0x10d7/0x18f0 [ 103.472712] SYSC_connect+0x1b8/0x300 [ 103.476488] SyS_connect+0x24/0x30 [ 103.480005] do_fast_syscall_32+0x2f7/0x870 [ 103.484313] entry_SYSENTER_compat+0x90/0xa2 [ 103.488703] [ 103.490307] Freed by task 4121: [ 103.493582] save_stack_trace+0x16/0x20 [ 103.497538] save_stack+0x43/0xd0 [ 103.500964] kasan_slab_free+0x72/0xc0 [ 103.504823] kfree+0xfb/0x310 [ 103.507902] l2tp_session_free+0x166/0x200 [ 103.512110] l2tp_tunnel_closeall+0x284/0x350 [ 103.516580] l2tp_udp_encap_destroy+0x87/0xe0 [ 103.521053] udp_destroy_sock+0x118/0x1a0 [ 103.525195] sk_common_release+0x6d/0x300 [ 103.529315] udp_lib_close+0x15/0x20 [ 103.533002] inet_release+0xff/0x1d0 [ 103.536700] sock_release+0x96/0x1c0 [ 103.540385] sock_close+0x16/0x20 [ 103.543809] __fput+0x263/0x700 [ 103.547059] ____fput+0x15/0x20 [ 103.550309] task_work_run+0x10c/0x180 [ 103.554166] exit_to_usermode_loop+0xfc/0x120 [ 103.558632] do_fast_syscall_32+0x5c3/0x870 [ 103.562920] entry_SYSENTER_compat+0x90/0xa2 [ 103.567292] [ 103.568896] The buggy address belongs to the object at ffff8801be4f2c80 [ 103.568896] which belongs to the cache kmalloc-512 of size 512 [ 103.581539] The buggy address is located 0 bytes inside of [ 103.581539] 512-byte region [ffff8801be4f2c80, ffff8801be4f2e80) [ 103.593208] The buggy address belongs to the page: [ 103.598107] page:ffffea0006f93c80 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 103.608280] flags: 0x8000000000004080(slab|head) [ 103.613005] page dumped because: kasan: bad access detected [ 103.618688] [ 103.620289] Memory state around the buggy address: [ 103.625191] ffff8801be4f2b80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc [ 103.632529] ffff8801be4f2c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 103.639857] >ffff8801be4f2c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 103.647193] ^ [ 103.650552] ffff8801be4f2d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 103.657926] ffff8801be4f2d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 103.665275] ================================================================== [ 103.672645] Disabling lock debugging due to kernel taint [ 103.678775] Kernel panic - not syncing: panic_on_warn set ... [ 103.678775] [ 103.686147] CPU: 1 PID: 4123 Comm: syz-executor0 Tainted: G B 4.9.109-ga4230be #2 [ 103.694896] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 103.704369] ffff8801b7b0fc00 ffffffff81eb3e29 ffffffff843c6327 00000000ffffffff [ 103.712437] 0000000000000000 0000000000000001 ffffffff83013be0 ffff8801b7b0fcc0 [ 103.720475] ffffffff81421925 0000000041b58ab3 ffffffff843b9a40 ffffffff81421766 [ 103.728516] Call Trace: [ 103.731097] [] dump_stack+0xc1/0x128 [ 103.736463] [] ? sock_release+0x1c0/0x1c0 [ 103.742259] [] panic+0x1bf/0x3bc [ 103.747283] [] ? add_taint.cold.6+0x16/0x16 [ 103.753271] [] ? ___preempt_schedule+0x16/0x18 [ 103.759506] [] kasan_end_report+0x47/0x4f [ 103.765302] [] kasan_report.cold.6+0x76/0x2fe [ 103.771453] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 103.778210] [] __asan_report_load4_noabort+0x14/0x20 [ 103.784969] [] l2tp_session_queue_purge+0xf4/0x100 [ 103.791554] [] ? sock_release+0x1c0/0x1c0 [ 103.797356] [] pppol2tp_release+0x1fb/0x2e0 [ 103.803332] [] sock_release+0x96/0x1c0 [ 103.808872] [] sock_close+0x16/0x20 [ 103.814155] [] __fput+0x263/0x700 [ 103.819259] [] ____fput+0x15/0x20 [ 103.824371] [] task_work_run+0x10c/0x180 [ 103.830081] [] exit_to_usermode_loop+0xfc/0x120 [ 103.836422] [] do_fast_syscall_32+0x5c3/0x870 [ 103.836436] [] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 103.836446] [] entry_SYSENTER_compat+0x90/0xa2 [ 103.843001] Dumping ftrace buffer: [ 103.843004] (ftrace buffer empty) [ 103.843007] Kernel Offset: disabled [ 103.866742] Rebooting in 86400 seconds..