[ OK ] Reached target Login Prompts. [ OK ] Reached target Multi-User System. [ OK ] Reached target Graphical Interface. Starting Update UTMP about System Runlevel Changes... [ OK ] Started Update UTMP about System Runlevel Changes. Debian GNU/Linux 9 syzkaller ttyS0 Warning: Permanently added '10.128.0.164' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 33.934908] ================================================================== [ 33.942336] BUG: KASAN: use-after-free in __lock_acquire+0x3098/0x4620 [ 33.948999] Read of size 8 at addr ffff8880985a5340 by task syz-executor686/6333 [ 33.956527] [ 33.958158] CPU: 1 PID: 6333 Comm: syz-executor686 Not tainted 4.14.175-syzkaller #0 [ 33.966029] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 33.975467] Call Trace: [ 33.978099] dump_stack+0x13e/0x194 [ 33.981710] ? __lock_acquire+0x3098/0x4620 [ 33.986016] print_address_description.cold+0x7c/0x1e2 [ 33.991388] ? __lock_acquire+0x3098/0x4620 [ 33.995702] kasan_report.cold+0xa9/0x2ae [ 33.999834] __lock_acquire+0x3098/0x4620 [ 34.003963] ? trace_hardirqs_on+0x10/0x10 [ 34.008217] ? __lock_acquire+0x5f7/0x4620 [ 34.012468] ? trace_hardirqs_on+0x10/0x10 [ 34.016831] ? trace_hardirqs_on+0x10/0x10 [ 34.021060] ? lock_acquire+0x170/0x3f0 [ 34.025015] ? eventpoll_release_file+0xae/0x130 [ 34.029753] ? eventpoll_release_file+0xae/0x130 [ 34.034488] lock_acquire+0x170/0x3f0 [ 34.038268] ? remove_wait_queue+0x1d/0x180 [ 34.042565] _raw_spin_lock_irqsave+0x8c/0xbf [ 34.047037] ? remove_wait_queue+0x1d/0x180 [ 34.051335] remove_wait_queue+0x1d/0x180 [ 34.055461] ep_unregister_pollwait.isra.0+0x9b/0x350 [ 34.060624] ep_remove+0x48/0x450 [ 34.064057] eventpoll_release_file+0xb9/0x130 [ 34.068613] __fput+0x53e/0x790 [ 34.071868] task_work_run+0x113/0x190 [ 34.075751] exit_to_usermode_loop+0x1d6/0x220 [ 34.080355] do_syscall_64+0x4a3/0x640 [ 34.084273] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 34.089452] RIP: 0033:0x4401d9 [ 34.092621] RSP: 002b:00007ffdcf3becd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000021 [ 34.100323] RAX: 0000000000000003 RBX: 00000000004002c8 RCX: 00000000004401d9 [ 34.107571] RDX: 00000000004401d9 RSI: 0000000000000003 RDI: 0000000000000004 [ 34.114832] RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8 [ 34.122095] R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000401a60 [ 34.129355] R13: 0000000000401af0 R14: 0000000000000000 R15: 0000000000000000 [ 34.136603] [ 34.138209] Allocated by task 6333: [ 34.141900] save_stack+0x32/0xa0 [ 34.145330] kasan_kmalloc+0xbf/0xe0 [ 34.149035] __kmalloc_node+0x4c/0x70 [ 34.152810] kvmalloc_node+0x46/0xd0 [ 34.156501] alloc_netdev_mqs+0x76/0xb70 [ 34.160536] ppp_ioctl+0x1313/0x221a [ 34.164250] do_vfs_ioctl+0x75a/0xfe0 [ 34.168118] SyS_ioctl+0x7f/0xb0 [ 34.171471] do_syscall_64+0x1d5/0x640 [ 34.175350] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 34.180524] [ 34.182137] Freed by task 6333: [ 34.185446] save_stack+0x32/0xa0 [ 34.188879] kasan_slab_free+0x75/0xc0 [ 34.192742] kfree+0xcb/0x260 [ 34.195824] kvfree+0x45/0x50 [ 34.198906] device_release+0x15f/0x1a0 [ 34.202858] kobject_put+0x13e/0x1f0 [ 34.206550] put_device+0x1c/0x30 [ 34.210025] free_netdev+0x26f/0x360 [ 34.213719] ppp_destroy_interface+0x2d7/0x3b0 [ 34.218323] ppp_release+0x122/0x1a0 [ 34.222031] ppp_ioctl+0x52d/0x221a [ 34.225637] do_vfs_ioctl+0x75a/0xfe0 [ 34.229428] SyS_ioctl+0x7f/0xb0 [ 34.232767] do_syscall_64+0x1d5/0x640 [ 34.236633] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 34.241797] [ 34.243406] The buggy address belongs to the object at ffff8880985a47c0 [ 34.243406] which belongs to the cache kmalloc-4096 of size 4096 [ 34.256240] The buggy address is located 2944 bytes inside of [ 34.256240] 4096-byte region [ffff8880985a47c0, ffff8880985a57c0) [ 34.268270] The buggy address belongs to the page: [ 34.273178] page:ffffea0002616900 count:1 mapcount:0 mapping:ffff8880985a47c0 index:0x0 compound_mapcount: 0 [ 34.283121] flags: 0xfffe0000008100(slab|head) [ 34.287683] raw: 00fffe0000008100 ffff8880985a47c0 0000000000000000 0000000100000001 [ 34.295538] raw: ffffea00029be3a0 ffffea00026169a0 ffff88812fe56dc0 0000000000000000 [ 34.303395] page dumped because: kasan: bad access detected [ 34.309239] [ 34.310844] Memory state around the buggy address: [ 34.315756] ffff8880985a5200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.323200] ffff8880985a5280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.332629] >ffff8880985a5300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.339971] ^ [ 34.345406] ffff8880985a5380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.352788] ffff8880985a5400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 34.360124] ================================================================== [ 34.367471] Disabling lock debugging due to kernel taint [ 34.372898] Kernel panic - not syncing: panic_on_warn set ... [ 34.372898] [ 34.380236] CPU: 1 PID: 6333 Comm: syz-executor686 Tainted: G B 4.14.175-syzkaller #0 [ 34.389304] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 34.398647] Call Trace: [ 34.401217] dump_stack+0x13e/0x194 [ 34.404934] panic+0x1f9/0x42d [ 34.408100] ? add_taint.cold+0x16/0x16 [ 34.412050] ? lock_downgrade+0x6e0/0x6e0 [ 34.416187] ? __lock_acquire+0x3098/0x4620 [ 34.420484] kasan_end_report+0x43/0x49 [ 34.424694] kasan_report.cold+0x12f/0x2ae [ 34.428903] __lock_acquire+0x3098/0x4620 [ 34.433041] ? trace_hardirqs_on+0x10/0x10 [ 34.437253] ? __lock_acquire+0x5f7/0x4620 [ 34.441463] ? trace_hardirqs_on+0x10/0x10 [ 34.445672] ? trace_hardirqs_on+0x10/0x10 [ 34.449878] ? lock_acquire+0x170/0x3f0 [ 34.453826] ? eventpoll_release_file+0xae/0x130 [ 34.458557] ? eventpoll_release_file+0xae/0x130 [ 34.463288] lock_acquire+0x170/0x3f0 [ 34.467066] ? remove_wait_queue+0x1d/0x180 [ 34.471379] _raw_spin_lock_irqsave+0x8c/0xbf [ 34.476110] ? remove_wait_queue+0x1d/0x180 [ 34.480405] remove_wait_queue+0x1d/0x180 [ 34.484528] ep_unregister_pollwait.isra.0+0x9b/0x350 [ 34.489693] ep_remove+0x48/0x450 [ 34.493120] eventpoll_release_file+0xb9/0x130 [ 34.497676] __fput+0x53e/0x790 [ 34.500935] task_work_run+0x113/0x190 [ 34.504816] exit_to_usermode_loop+0x1d6/0x220 [ 34.509461] do_syscall_64+0x4a3/0x640 [ 34.513325] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 34.518503] RIP: 0033:0x4401d9 [ 34.521669] RSP: 002b:00007ffdcf3becd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000021 [ 34.529353] RAX: 0000000000000003 RBX: 00000000004002c8 RCX: 00000000004401d9 [ 34.536596] RDX: 00000000004401d9 RSI: 0000000000000003 RDI: 0000000000000004 [ 34.543841] RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8 [ 34.551101] R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000401a60 [ 34.558349] R13: 0000000000401af0 R14: 0000000000000000 R15: 0000000000000000 [ 34.566808] Kernel Offset: disabled [ 34.570444] Rebooting in 86400 seconds..