random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) random: sshd: uninitialized urandom read (32 bytes read, 32 bits of entropy available) random: sshd: uninitialized urandom read (32 bytes read, 120 bits of entropy available) random: nonblocking pool is initialized ================================================================== BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xe8/0x100 net/l2tp/l2tp_core.c:830 Read of size 4 at addr ffff8800b0626780 by task syzkaller187593/3692 CPU: 1 PID: 3692 Comm: syzkaller187593 Not tainted 4.4.125-g38f41ec #63 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 018a296bd339e121 ffff8801cbcefcc0 ffffffff81d067bd ffffea0002c18980 ffff8800b0626780 0000000000000000 ffff8800b0626780 ffffffff82ded950 ffff8801cbcefcf8 ffffffff814fea83 ffff8800b0626780 Call Trace: [<ffffffff81d067bd>] __dump_stack lib/dump_stack.c:15 [inline] [<ffffffff81d067bd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [<ffffffff814fea83>] print_address_description+0x73/0x260 mm/kasan/report.c:252 [<ffffffff814fef95>] kasan_report_error mm/kasan/report.c:351 [inline] [<ffffffff814fef95>] kasan_report+0x285/0x370 mm/kasan/report.c:408 [<ffffffff814ff0d4>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428 [<ffffffff8345ee78>] l2tp_session_queue_purge+0xe8/0x100 net/l2tp/l2tp_core.c:830 [<ffffffff8346bf0f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509 [<ffffffff82ded7fd>] sock_release+0x8d/0x1e0 net/socket.c:586 [<ffffffff82ded966>] sock_close+0x16/0x20 net/socket.c:1037 [<ffffffff81523f43>] __fput+0x233/0x6d0 fs/file_table.c:208 [<ffffffff81524465>] ____fput+0x15/0x20 fs/file_table.c:244 [<ffffffff8118bd44>] task_work_run+0x104/0x180 kernel/task_work.c:115 [<ffffffff8100361d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [<ffffffff8100361d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:252 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline] [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:348 [<ffffffff83779af5>] int_ret_from_sys_call+0x25/0xa3 Allocated by task 3691: [<ffffffff81035d76>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 [<ffffffff814fdaf3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 [<ffffffff814fddbd>] set_track mm/kasan/kasan.c:524 [inline] [<ffffffff814fddbd>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616 [<ffffffff814fa0a4>] __kmalloc+0x124/0x320 mm/slub.c:3613 [<ffffffff83464d89>] kmalloc include/linux/slab.h:481 [inline] [<ffffffff83464d89>] kzalloc include/linux/slab.h:620 [inline] [<ffffffff83464d89>] l2tp_session_create+0x39/0x10f0 net/l2tp/l2tp_core.c:1744 [<ffffffff8346941c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718 [<ffffffff82df21b6>] SYSC_connect+0x1b6/0x310 net/socket.c:1557 [<ffffffff82df4a24>] SyS_connect+0x24/0x30 net/socket.c:1538 [<ffffffff83779965>] entry_SYSCALL_64_fastpath+0x22/0x9e Freed by task 3691: [<ffffffff81035d76>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 [<ffffffff814fdaf3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 [<ffffffff814fe412>] set_track mm/kasan/kasan.c:524 [inline] [<ffffffff814fe412>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589 [<ffffffff814faeac>] slab_free_hook mm/slub.c:1383 [inline] [<ffffffff814faeac>] slab_free_freelist_hook mm/slub.c:1405 [inline] [<ffffffff814faeac>] slab_free mm/slub.c:2859 [inline] [<ffffffff814faeac>] kfree+0xfc/0x300 mm/slub.c:3749 [<ffffffff83461310>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1672 [<ffffffff83463bc1>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline] [<ffffffff83463bc1>] l2tp_tunnel_closeall+0x2d1/0x3b0 net/l2tp/l2tp_core.c:1279 [<ffffffff8346472b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300 [<ffffffff833729c1>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421 [<ffffffff82e048fb>] sk_common_release+0x6b/0x300 net/core/sock.c:2680 [<ffffffff83371975>] udp_lib_close+0x15/0x20 include/net/udp.h:190 [<ffffffff831d5eba>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435 [<ffffffff832fb320>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424 [<ffffffff82ded7fd>] sock_release+0x8d/0x1e0 net/socket.c:586 [<ffffffff82ded966>] sock_close+0x16/0x20 net/socket.c:1037 [<ffffffff81523f43>] __fput+0x233/0x6d0 fs/file_table.c:208 [<ffffffff81524465>] ____fput+0x15/0x20 fs/file_table.c:244 [<ffffffff8118bd44>] task_work_run+0x104/0x180 kernel/task_work.c:115 [<ffffffff8100361d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [<ffffffff8100361d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:252 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline] [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:348 [<ffffffff83779af5>] int_ret_from_sys_call+0x25/0xa3 The buggy address belongs to the object at ffff8800b0626780 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff8800b0626780, ffff8800b0626980) The buggy address belongs to the page: PANIC: double fault, error_code: 0x0 CPU: 1 PID: 3692 Comm: syzkaller187593 Not tainted 4.4.125-g38f41ec #63 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801cd331800 task.stack: ffff8801cbce8000 RIP: 0010:[<ffffffff81491182>] [<ffffffff81491182>] dump_page_badflags+0x12/0x250 mm/debug.c:84 RSP: 0018:ffff880100000000 EFLAGS: 00010046 RAX: ffff8801cd331800 RBX: ffffea0002c18980 RCX: ffffffff814912f0 RDX: 0000000000000000 RSI: ffffffff838a91a0 RDI: ffffea0002c18980 RBP: ffff880100000020 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000002 R11: fffffbfff0ad821e R12: 0000000000000000 R13: ffffffff838a91a0 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f529b180700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8800fffffff8 CR3: 00000000b4a10000 CR4: 0000000000160670 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: Call Trace: <UNK> Code: 00 e9 50 fd ff ff e8 7e df 06 00 e9 1d fd ff ff 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 49 89 f5 41 54 49 89 d4 <53> 48 89 fb 48 83 ec 08 e8 f1 04 ed ff 48 8d 7b 10 48 b8 00 00