Debian GNU/Linux 7 syzkaller ttyS0 net.ipv6.conf.syz0.accept_dad = 0 net.ipv6.conf.syz0.router_solicitations = 0 executing program syzkaller login: [ 37.939386] ================================================================== [ 37.940360] BUG: KASAN: use-after-free in detach_if_pending+0x557/0x610 [ 37.941049] Write of size 8 at addr ffff88006ae2b680 by task syzkaller048766/2979 [ 37.941602] [ 37.941738] CPU: 2 PID: 2979 Comm: syzkaller048766 Not tainted 4.13.0-next-20170905+ #15 [ 37.942375] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 37.943000] Call Trace: [ 37.943209] dump_stack+0x194/0x257 [ 37.943499] ? arch_local_irq_restore+0x53/0x53 [ 37.943848] ? show_regs_print_info+0x65/0x65 [ 37.944303] ? lock_timer_base+0x1a3/0x2b0 [ 37.945054] ? detach_if_pending+0x557/0x610 [ 37.945928] print_address_description+0x73/0x250 [ 37.946898] ? detach_if_pending+0x557/0x610 [ 37.947782] kasan_report+0x24e/0x340 [ 37.948515] __asan_report_store8_noabort+0x17/0x20 [ 37.949495] detach_if_pending+0x557/0x610 [ 37.950386] ? trace_raw_output_tick_stop+0x130/0x130 [ 37.951441] ? _raw_spin_lock_irqsave+0x9e/0xc0 [ 37.952366] ? lock_timer_base+0x1a3/0x2b0 [ 37.954518] ? lock_timer_base+0x1eb/0x2b0 [ 37.955351] ? __internal_add_timer+0x2d0/0x2d0 [ 37.956291] ? trace_hardirqs_on+0xd/0x10 [ 37.957159] try_to_del_timer_sync+0xa2/0x120 [ 37.958068] ? del_timer+0x130/0x130 [ 37.958827] ? del_timer_sync+0xeb/0x240 [ 37.959671] del_timer_sync+0x18a/0x240 [ 37.960481] tun_free_netdev+0x105/0x1b0 [ 37.961299] ? tun_xdp+0x410/0x410 [ 37.962000] ? cpumask_next+0x24/0x30 [ 37.962764] ? netdev_refcnt_read+0xed/0x150 [ 37.963652] ? tun_xdp+0x410/0x410 [ 37.964366] netdev_run_todo+0x870/0xca0 [ 37.965196] ? do_group_exit+0x149/0x400 [ 37.966016] ? register_netdev+0x30/0x30 [ 37.966831] ? lock_downgrade+0x990/0x990 [ 37.967663] ? trace_hardirqs_on+0xd/0x10 [ 37.968523] ? refcount_sub_and_test+0x115/0x1b0 [ 37.969486] ? refcount_inc+0x50/0x50 [ 37.970277] ? refcount_inc+0x50/0x50 [ 37.971047] ? sk_destruct+0x4c/0x80 [ 37.971797] ? __sk_free+0x5c/0x230 [ 37.972554] ? sk_free+0x2f/0x40 [ 37.973216] ? __tun_detach+0x176/0x1390 [ 37.974907] ? tun_attach+0xf90/0xf90 [ 37.975682] ? do_raw_spin_trylock+0x190/0x190 [ 37.976416] ? locks_remove_file+0x3fa/0x5a0 [ 37.977356] ? fcntl_setlk+0x10d0/0x10d0 [ 37.978222] ? __fsnotify_parent+0xb4/0x3a0 [ 37.979139] ? fsnotify+0x1af0/0x1af0 [ 37.979944] ? __tun_detach+0x1390/0x1390 [ 37.980828] ? __tun_detach+0x1390/0x1390 [ 37.981715] rtnl_unlock+0xe/0x10 [ 37.982436] tun_chr_close+0x49/0x60 [ 37.983206] __fput+0x333/0x7f0 [ 37.983915] ? fput+0x140/0x140 [ 37.984615] ? check_same_owner+0x320/0x320 [ 37.985512] ? _raw_spin_unlock_irq+0x27/0x70 [ 37.986423] ____fput+0x15/0x20 [ 37.987084] task_work_run+0x199/0x270 [ 37.987866] ? task_work_cancel+0x210/0x210 [ 37.988742] ? _raw_spin_unlock+0x22/0x30 [ 37.989594] ? switch_task_namespaces+0x87/0xc0 [ 37.990587] do_exit+0xa52/0x1b40 [ 37.991285] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 37.992293] ? check_noncircular+0x20/0x20 [ 37.993159] ? __handle_mm_fault+0x587/0x39c0 [ 37.994061] ? mm_update_next_owner+0x930/0x930 [ 37.995571] ? __pmd_alloc+0x4e0/0x4e0 [ 37.996373] ? find_held_lock+0x39/0x1d0 [ 37.997256] ? lock_downgrade+0x990/0x990 [ 37.998150] ? handle_mm_fault+0x4a2/0x860 [ 37.999028] ? down_read_trylock+0xdb/0x170 [ 37.999919] ? __handle_mm_fault+0x39c0/0x39c0 [ 38.000873] ? vmacache_find+0x61/0x270 [ 38.001711] ? up_read+0x1a/0x40 [ 38.002415] ? __do_page_fault+0x35b/0xb60 [ 38.003368] ? do_page_fault+0xee/0x720 [ 38.004256] ? __do_page_fault+0xb60/0xb60 [ 38.005157] ? putname+0xf3/0x130 [ 38.005900] do_group_exit+0x149/0x400 [ 38.006701] ? lockdep_sys_exit+0x47/0xf0 [ 38.007563] ? SyS_exit+0x30/0x30 [ 38.008281] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 38.009329] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 38.010131] SyS_exit_group+0x1d/0x20 [ 38.010511] entry_SYSCALL_64_fastpath+0x1f/0xbe [ 38.010978] RIP: 0033:0x438db9 [ 38.011302] RSP: 002b:00007fffa2853f98 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 38.012069] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000438db9 [ 38.012951] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 38.014183] RBP: 0000000000000082 R08: 000000000000003c R09: 00000000000000e7 [ 38.015460] R10: ffffffffffffffcc R11: 0000000000000246 R12: 0000000000000001 [ 38.017271] R13: 00000000006cc300 R14: 00000000004028b0 R15: 0000000000000000 [ 38.018363] [ 38.018614] Allocated by task 2979: [ 38.019166] save_stack_trace+0x16/0x20 [ 38.019761] save_stack+0x43/0xd0 [ 38.020308] kasan_kmalloc+0xad/0xe0 [ 38.020885] __kmalloc_node+0x47/0x70 [ 38.021464] kvmalloc_node+0x64/0xd0 [ 38.021974] alloc_netdev_mqs+0x16e/0xed0 [ 38.022613] __tun_chr_ioctl+0x12be/0x3d20 [ 38.023255] tun_chr_ioctl+0x2a/0x40 [ 38.023822] do_vfs_ioctl+0x1b1/0x1530 [ 38.024403] SyS_ioctl+0x8f/0xc0 [ 38.025036] entry_SYSCALL_64_fastpath+0x1f/0xbe [ 38.025956] [ 38.026268] Freed by task 2979: [ 38.026874] save_stack_trace+0x16/0x20 [ 38.027651] save_stack+0x43/0xd0 [ 38.028320] kasan_slab_free+0x71/0xc0 [ 38.029113] kfree+0xca/0x250 [ 38.029738] kvfree+0x36/0x60 [ 38.030363] free_netdev+0x2cf/0x360 [ 38.031137] __tun_chr_ioctl+0x2cf6/0x3d20 [ 38.032028] tun_chr_ioctl+0x2a/0x40 [ 38.032468] do_vfs_ioctl+0x1b1/0x1530 [ 38.032872] SyS_ioctl+0x8f/0xc0 [ 38.033294] entry_SYSCALL_64_fastpath+0x1f/0xbe [ 38.033776] [ 38.033948] The buggy address belongs to the object at ffff88006ae28280 [ 38.033948] which belongs to the cache kmalloc-16384 of size 16384 [ 38.035361] The buggy address is located 13312 bytes inside of [ 38.035361] 16384-byte region [ffff88006ae28280, ffff88006ae2c280) [ 38.036657] The buggy address belongs to the page: [ 38.037240] page:ffffea0001ab8a00 count:1 mapcount:0 mapping:ffff88006ae28280 index:0x0 compound_mapcount: 0 [ 38.038776] flags: 0x500000000008100(slab|head) [ 38.039317] raw: 0500000000008100 ffff88006ae28280 0000000000000000 0000000100000001 [ 38.040163] raw: ffffea0001a10c20 ffff88006d800c50 ffff88003e802200 0000000000000000 [ 38.040978] page dumped because: kasan: bad access detected [ 38.041659] [ 38.041831] Memory state around the buggy address: [ 38.042399] ffff88006ae2b580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 38.043213] ffff88006ae2b600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 38.043949] >ffff88006ae2b680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 38.044758] ^ [ 38.045182] ffff88006ae2b700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 38.045910] ffff88006ae2b780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 38.046694] ================================================================== [ 38.047496] Disabling lock debugging due to kernel taint [ 38.048080] Kernel panic - not syncing: panic_on_warn set ... [ 38.048080] [ 38.048853] CPU: 2 PID: 2979 Comm: syzkaller048766 Tainted: G B 4.13.0-next-20170905+ #15 [ 38.049853] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 38.050713] Call Trace: [ 38.050977] dump_stack+0x194/0x257 [ 38.051410] ? arch_local_irq_restore+0x53/0x53 [ 38.051866] ? vprintk_default+0x28/0x30 [ 38.052324] ? detach_if_pending+0x530/0x610 [ 38.052781] panic+0x1e4/0x417 [ 38.053168] ? __warn+0x1d9/0x1d9 [ 38.053528] ? detach_if_pending+0x557/0x610 [ 38.053957] kasan_end_report+0x50/0x50 [ 38.054399] kasan_report+0x137/0x340 [ 38.054796] __asan_report_store8_noabort+0x17/0x20 [ 38.055345] detach_if_pending+0x557/0x610 [ 38.055775] ? trace_raw_output_tick_stop+0x130/0x130 [ 38.056350] ? _raw_spin_lock_irqsave+0x9e/0xc0 [ 38.056835] ? lock_timer_base+0x1a3/0x2b0 [ 38.057326] ? lock_timer_base+0x1eb/0x2b0 [ 38.057756] ? __internal_add_timer+0x2d0/0x2d0 [ 38.058272] ? trace_hardirqs_on+0xd/0x10 [ 38.059098] try_to_del_timer_sync+0xa2/0x120 [ 38.059557] ? del_timer+0x130/0x130 [ 38.059934] ? del_timer_sync+0xeb/0x240 [ 38.060392] del_timer_sync+0x18a/0x240 [ 38.060824] tun_free_netdev+0x105/0x1b0 [ 38.061307] ? tun_xdp+0x410/0x410 [ 38.061667] ? cpumask_next+0x24/0x30 [ 38.062085] ? netdev_refcnt_read+0xed/0x150 [ 38.062529] ? tun_xdp+0x410/0x410 [ 38.062886] netdev_run_todo+0x870/0xca0 [ 38.063324] ? do_group_exit+0x149/0x400 [ 38.063735] ? register_netdev+0x30/0x30 [ 38.064184] ? lock_downgrade+0x990/0x990 [ 38.064610] ? trace_hardirqs_on+0xd/0x10 [ 38.065084] ? refcount_sub_and_test+0x115/0x1b0 [ 38.065581] ? refcount_inc+0x50/0x50 [ 38.065966] ? refcount_inc+0x50/0x50 [ 38.066383] ? sk_destruct+0x4c/0x80 [ 38.066764] ? __sk_free+0x5c/0x230 [ 38.067168] ? sk_free+0x2f/0x40 [ 38.067513] ? __tun_detach+0x176/0x1390 [ 38.067928] ? tun_attach+0xf90/0xf90 [ 38.068364] ? do_raw_spin_trylock+0x190/0x190 [ 38.068841] ? locks_remove_file+0x3fa/0x5a0 [ 38.069343] ? fcntl_setlk+0x10d0/0x10d0 [ 38.069751] ? __fsnotify_parent+0xb4/0x3a0 [ 38.070236] ? fsnotify+0x1af0/0x1af0 [ 38.070635] ? __tun_detach+0x1390/0x1390 [ 38.071050] ? __tun_detach+0x1390/0x1390 [ 38.071481] rtnl_unlock+0xe/0x10 [ 38.071828] tun_chr_close+0x49/0x60 [ 38.072216] __fput+0x333/0x7f0 [ 38.072559] ? fput+0x140/0x140 [ 38.072883] ? check_same_owner+0x320/0x320 [ 38.073354] ? _raw_spin_unlock_irq+0x27/0x70 [ 38.073793] ____fput+0x15/0x20 [ 38.074129] task_work_run+0x199/0x270 [ 38.074511] ? task_work_cancel+0x210/0x210 [ 38.074931] ? _raw_spin_unlock+0x22/0x30 [ 38.075354] ? switch_task_namespaces+0x87/0xc0 [ 38.075812] do_exit+0xa52/0x1b40 [ 38.076167] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 38.076675] ? check_noncircular+0x20/0x20 [ 38.077137] ? __handle_mm_fault+0x587/0x39c0 [ 38.077585] ? mm_update_next_owner+0x930/0x930 [ 38.078048] ? __pmd_alloc+0x4e0/0x4e0 [ 38.078455] ? find_held_lock+0x39/0x1d0 [ 38.078866] ? lock_downgrade+0x990/0x990 [ 38.079305] ? handle_mm_fault+0x4a2/0x860 [ 38.079723] ? down_read_trylock+0xdb/0x170 [ 38.080165] ? __handle_mm_fault+0x39c0/0x39c0 [ 38.080604] ? vmacache_find+0x61/0x270 [ 38.081334] ? up_read+0x1a/0x40 [ 38.081686] ? __do_page_fault+0x35b/0xb60 [ 38.082011] ? do_page_fault+0xee/0x720 [ 38.082314] ? __do_page_fault+0xb60/0xb60 [ 38.082617] ? putname+0xf3/0x130 [ 38.082891] do_group_exit+0x149/0x400 [ 38.083207] ? lockdep_sys_exit+0x47/0xf0 [ 38.083499] ? SyS_exit+0x30/0x30 [ 38.083751] ? trace_hardirqs_on_caller+0x421/0x5c0 [ 38.084160] ? trace_hardirqs_on_thunk+0x1a/0x1c [ 38.084507] SyS_exit_group+0x1d/0x20 [ 38.084888] entry_SYSCALL_64_fastpath+0x1f/0xbe [ 38.085412] RIP: 0033:0x438db9 [ 38.085722] RSP: 002b:00007fffa2853f98 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 38.086425] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000438db9 [ 38.087159] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 38.087878] RBP: 0000000000000082 R08: 000000000000003c R09: 00000000000000e7 [ 38.088659] R10: ffffffffffffffcc R11: 0000000000000246 R12: 0000000000000001 [ 38.089491] R13: 00000000006cc300 R14: 00000000004028b0 R15: 0000000000000000 [ 38.090378] Dumping ftrace buffer: [ 38.090728] (ftrace buffer empty) [ 38.091100] Kernel Offset: disabled [ 38.091459] Rebooting in 86400 seconds..