[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.552977] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 21.256045] random: sshd: uninitialized urandom read (32 bytes read) [ 21.596045] random: sshd: uninitialized urandom read (32 bytes read) [ 22.250835] random: sshd: uninitialized urandom read (32 bytes read) [ 22.378227] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.56' (ECDSA) to the list of known hosts. [ 27.777467] random: sshd: uninitialized urandom read (32 bytes read) executing program [ 27.921350] ================================================================== [ 27.928759] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 27.936007] Read of size 4 at addr ffff8801b5025900 by task syz-executor354/3805 [ 27.943513] [ 27.945117] CPU: 0 PID: 3805 Comm: syz-executor354 Not tainted 4.9.99-gc462abb #20 [ 27.952797] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 27.962130] ffff8801b64cfcb0 ffffffff81eb0f09 ffffea0006d40900 ffff8801b5025900 [ 27.970121] 0000000000000000 ffff8801b5025900 ffffffff8300fbe0 ffff8801b64cfce8 [ 27.978112] ffffffff815652eb ffff8801b5025900 0000000000000004 0000000000000000 [ 27.986100] Call Trace: [ 27.988666] [] dump_stack+0xc1/0x128 [ 27.994007] [] ? sock_release+0x1c0/0x1c0 [ 27.999783] [] print_address_description+0x6c/0x234 [ 28.006427] [] ? sock_release+0x1c0/0x1c0 [ 28.012199] [] kasan_report.cold.6+0x242/0x2fe [ 28.018418] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 28.025150] [] __asan_report_load4_noabort+0x14/0x20 [ 28.031880] [] l2tp_session_queue_purge+0xf4/0x100 [ 28.038436] [] ? sock_release+0x1c0/0x1c0 [ 28.044208] [] pppol2tp_release+0x1fb/0x2e0 [ 28.050154] [] sock_release+0x96/0x1c0 [ 28.055668] [] sock_close+0x16/0x20 [ 28.060924] [] __fput+0x263/0x700 [ 28.066005] [] ____fput+0x15/0x20 [ 28.071085] [] task_work_run+0x10c/0x180 [ 28.076772] [] exit_to_usermode_loop+0xfc/0x120 [ 28.083068] [] do_syscall_64+0x364/0x490 [ 28.088758] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 28.095658] [ 28.097262] Allocated by task 3804: [ 28.100869] save_stack_trace+0x16/0x20 [ 28.104818] save_stack+0x43/0xd0 [ 28.108243] kasan_kmalloc+0xc7/0xe0 [ 28.111941] __kmalloc+0x11d/0x300 [ 28.115460] l2tp_session_create+0x38/0x16f0 [ 28.119842] pppol2tp_connect+0x10d7/0x18f0 [ 28.124142] SYSC_connect+0x1b8/0x300 [ 28.127915] SyS_connect+0x24/0x30 [ 28.131429] do_syscall_64+0x1a6/0x490 [ 28.135291] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 28.140365] [ 28.141969] Freed by task 3804: [ 28.145225] save_stack_trace+0x16/0x20 [ 28.149175] save_stack+0x43/0xd0 [ 28.152603] kasan_slab_free+0x72/0xc0 [ 28.156467] kfree+0xfb/0x310 [ 28.159549] l2tp_session_free+0x166/0x200 [ 28.163761] l2tp_tunnel_closeall+0x284/0x350 [ 28.168232] l2tp_udp_encap_destroy+0x87/0xe0 [ 28.172703] udpv6_destroy_sock+0xb1/0xd0 [ 28.176832] sk_common_release+0x6d/0x300 [ 28.180953] udp_lib_close+0x15/0x20 [ 28.184641] inet_release+0xff/0x1d0 [ 28.188334] inet6_release+0x50/0x70 [ 28.192020] sock_release+0x96/0x1c0 [ 28.195707] sock_close+0x16/0x20 [ 28.199136] __fput+0x263/0x700 [ 28.202387] ____fput+0x15/0x20 [ 28.205643] task_work_run+0x10c/0x180 [ 28.209506] exit_to_usermode_loop+0xfc/0x120 [ 28.213973] do_syscall_64+0x364/0x490 [ 28.217837] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 28.222926] [ 28.224531] The buggy address belongs to the object at ffff8801b5025900 [ 28.224531] which belongs to the cache kmalloc-512 of size 512 [ 28.237166] The buggy address is located 0 bytes inside of [ 28.237166] 512-byte region [ffff8801b5025900, ffff8801b5025b00) [ 28.248843] The buggy address belongs to the page: [ 28.253750] page:ffffea0006d40900 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 28.263933] flags: 0x8000000000004080(slab|head) [ 28.268672] page dumped because: kasan: bad access detected [ 28.274354] [ 28.275967] Memory state around the buggy address: [ 28.280869] ffff8801b5025800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 28.288206] ffff8801b5025880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 28.295541] >ffff8801b5025900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 28.302874] ^ [ 28.306214] ffff8801b5025980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 28.313552] ffff8801b5025a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 28.320884] ================================================================== [ 28.328214] Disabling lock debugging due to kernel taint [ 28.334042] Kernel panic - not syncing: panic_on_warn set ... [ 28.334042] [ 28.341390] CPU: 0 PID: 3805 Comm: syz-executor354 Tainted: G B 4.9.99-gc462abb #20 [ 28.350290] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 28.359628] ffff8801b64cfc10 ffffffff81eb0f09 ffffffff843c4fe5 00000000ffffffff [ 28.367634] 0000000000000000 0000000000000000 ffffffff8300fbe0 ffff8801b64cfcd0 [ 28.375617] ffffffff8141f855 0000000041b58ab3 ffffffff843b86e8 ffffffff8141f696 [ 28.383602] Call Trace: [ 28.386172] [] dump_stack+0xc1/0x128 [ 28.391513] [] ? sock_release+0x1c0/0x1c0 [ 28.397290] [] panic+0x1bf/0x3bc [ 28.402282] [] ? add_taint.cold.6+0x16/0x16 [ 28.408234] [] ? ___preempt_schedule+0x16/0x18 [ 28.414442] [] kasan_end_report+0x47/0x4f [ 28.420216] [] kasan_report.cold.6+0x76/0x2fe [ 28.426342] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 28.433076] [] __asan_report_load4_noabort+0x14/0x20 [ 28.439805] [] l2tp_session_queue_purge+0xf4/0x100 [ 28.446362] [] ? sock_release+0x1c0/0x1c0 [ 28.452136] [] pppol2tp_release+0x1fb/0x2e0 [ 28.458085] [] sock_release+0x96/0x1c0 [ 28.463597] [] sock_close+0x16/0x20 [ 28.468853] [] __fput+0x263/0x700 [ 28.473933] [] ____fput+0x15/0x20 [ 28.479012] [] task_work_run+0x10c/0x180 [ 28.484700] [] exit_to_usermode_loop+0xfc/0x120 [ 28.490997] [] do_syscall_64+0x364/0x490 [ 28.496686] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 28.504051] Dumping ftrace buffer: [ 28.507566] (ftrace buffer empty) [ 28.511254] Kernel Offset: disabled [ 28.514857] Rebooting in 86400 seconds..