[....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[ 13.057441] random: sshd: uninitialized urandom read (32 bytes read) [?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 syzkaller login: [ 14.771723] random: sshd: uninitialized urandom read (32 bytes read) [ 15.082464] random: sshd: uninitialized urandom read (32 bytes read) [ 15.912015] random: sshd: uninitialized urandom read (32 bytes read) [ 16.049014] random: sshd: uninitialized urandom read (32 bytes read) Warning: Permanently added '10.128.10.14' (ECDSA) to the list of known hosts. [ 21.500823] random: sshd: uninitialized urandom read (32 bytes read) executing program executing program [ 21.725059] ================================================================== [ 21.732452] BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 [ 21.739719] Read of size 4 at addr ffff8801b5633b80 by task syz-executor964/3807 [ 21.747222] [ 21.748827] CPU: 1 PID: 3807 Comm: syz-executor964 Not tainted 4.9.110-g00a0bcb #4 [ 21.756512] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 21.765839] ffff8801beb17cb0 ffffffff81eb2329 ffffea0006d58c80 ffff8801b5633b80 [ 21.773849] 0000000000000000 ffff8801b5633b80 ffffffff83011be0 ffff8801beb17ce8 [ 21.781851] ffffffff81567a89 ffff8801b5633b80 0000000000000004 0000000000000000 [ 21.789852] Call Trace: [ 21.792424] [] dump_stack+0xc1/0x128 [ 21.797765] [] ? sock_release+0x1c0/0x1c0 [ 21.803537] [] print_address_description+0x6c/0x234 [ 21.810174] [] ? sock_release+0x1c0/0x1c0 [ 21.815945] [] kasan_report.cold.6+0x242/0x2fe [ 21.822155] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 21.828882] [] __asan_report_load4_noabort+0x14/0x20 [ 21.835607] [] l2tp_session_queue_purge+0xf4/0x100 [ 21.842158] [] ? sock_release+0x1c0/0x1c0 [ 21.847941] [] pppol2tp_release+0x1fb/0x2e0 [ 21.853885] [] sock_release+0x96/0x1c0 [ 21.859397] [] sock_close+0x16/0x20 [ 21.864646] [] __fput+0x263/0x700 [ 21.869721] [] ____fput+0x15/0x20 [ 21.874794] [] task_work_run+0x10c/0x180 [ 21.880486] [] exit_to_usermode_loop+0xfc/0x120 [ 21.886775] [] do_syscall_64+0x364/0x490 [ 21.892457] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 21.899360] [ 21.900962] Allocated by task 3805: [ 21.904563] save_stack_trace+0x16/0x20 [ 21.908505] save_stack+0x43/0xd0 [ 21.911927] kasan_kmalloc+0xc7/0xe0 [ 21.915613] __kmalloc+0x11d/0x300 [ 21.919126] l2tp_session_create+0x38/0x16f0 [ 21.923502] pppol2tp_connect+0x10d7/0x18f0 [ 21.927797] SYSC_connect+0x1b8/0x300 [ 21.931568] SyS_connect+0x24/0x30 [ 21.935082] do_syscall_64+0x1a6/0x490 [ 21.938943] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 21.944019] [ 21.945620] Freed by task 3805: [ 21.948873] save_stack_trace+0x16/0x20 [ 21.952817] save_stack+0x43/0xd0 [ 21.956241] kasan_slab_free+0x72/0xc0 [ 21.960099] kfree+0xfb/0x310 [ 21.963177] l2tp_session_free+0x166/0x200 [ 21.967385] l2tp_tunnel_closeall+0x284/0x350 [ 21.971851] l2tp_udp_encap_destroy+0x87/0xe0 [ 21.976317] udpv6_destroy_sock+0xb1/0xd0 [ 21.980434] sk_common_release+0x6d/0x300 [ 21.984554] udp_lib_close+0x15/0x20 [ 21.988239] inet_release+0xff/0x1d0 [ 21.991922] inet6_release+0x50/0x70 [ 21.995606] sock_release+0x96/0x1c0 [ 21.999288] sock_close+0x16/0x20 [ 22.002713] __fput+0x263/0x700 [ 22.005961] ____fput+0x15/0x20 [ 22.009220] task_work_run+0x10c/0x180 [ 22.013080] exit_to_usermode_loop+0xfc/0x120 [ 22.017546] do_syscall_64+0x364/0x490 [ 22.021403] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 22.026475] [ 22.028076] The buggy address belongs to the object at ffff8801b5633b80 [ 22.028076] which belongs to the cache kmalloc-512 of size 512 [ 22.040711] The buggy address is located 0 bytes inside of [ 22.040711] 512-byte region [ffff8801b5633b80, ffff8801b5633d80) [ 22.052387] The buggy address belongs to the page: [ 22.057291] page:ffffea0006d58c80 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 [ 22.067458] flags: 0x8000000000004080(slab|head) [ 22.072180] page dumped because: kasan: bad access detected [ 22.077858] [ 22.079458] Memory state around the buggy address: [ 22.084357] ffff8801b5633a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 22.091684] ffff8801b5633b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 22.099015] >ffff8801b5633b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 22.106342] ^ [ 22.109679] ffff8801b5633c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 22.117008] ffff8801b5633c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 22.124334] ================================================================== [ 22.131661] Disabling lock debugging due to kernel taint [ 22.137169] Kernel panic - not syncing: panic_on_warn set ... [ 22.137169] [ 22.144520] CPU: 1 PID: 3807 Comm: syz-executor964 Tainted: G B 4.9.110-g00a0bcb #4 [ 22.153413] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 22.162748] ffff8801beb17c10 ffffffff81eb2329 ffffffff843c7167 00000000ffffffff [ 22.170748] 0000000000000000 0000000000000001 ffffffff83011be0 ffff8801beb17cd0 [ 22.178751] ffffffff81421925 0000000041b58ab3 ffffffff843ba880 ffffffff81421766 [ 22.186756] Call Trace: [ 22.189318] [] dump_stack+0xc1/0x128 [ 22.194667] [] ? sock_release+0x1c0/0x1c0 [ 22.200454] [] panic+0x1bf/0x3bc [ 22.205460] [] ? add_taint.cold.6+0x16/0x16 [ 22.211410] [] ? ___preempt_schedule+0x16/0x18 [ 22.217621] [] kasan_end_report+0x47/0x4f [ 22.223395] [] kasan_report.cold.6+0x76/0x2fe [ 22.229516] [] ? l2tp_session_queue_purge+0xf4/0x100 [ 22.236241] [] __asan_report_load4_noabort+0x14/0x20 [ 22.242972] [] l2tp_session_queue_purge+0xf4/0x100 [ 22.249543] [] ? sock_release+0x1c0/0x1c0 [ 22.255406] [] pppol2tp_release+0x1fb/0x2e0 [ 22.261436] [] sock_release+0x96/0x1c0 [ 22.266946] [] sock_close+0x16/0x20 [ 22.273942] [] __fput+0x263/0x700 [ 22.279113] [] ____fput+0x15/0x20 [ 22.284192] [] task_work_run+0x10c/0x180 [ 22.289878] [] exit_to_usermode_loop+0xfc/0x120 [ 22.296172] [] do_syscall_64+0x364/0x490 [ 22.301859] [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb [ 22.309380] Dumping ftrace buffer: [ 22.312901] (ftrace buffer empty) [ 22.316581] Kernel Offset: disabled [ 22.320181] Rebooting in 86400 seconds..