[....] Starting enhanced syslogd: rsyslogd[ 14.756731] audit: type=1400 audit(1559984490.759:4): avc: denied { syslog } for pid=1926 comm="rsyslogd" capability=34 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=capability2 permissive=1 [?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[1G[[32m ok [39;49m8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.228' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program syzkaller login: [ 50.375652] ================================================================== [ 50.383225] BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 [ 50.389986] Read of size 8 at addr ffff8800b66c51e8 by task syz-executor525/2114 [ 50.397633] [ 50.399251] CPU: 0 PID: 2114 Comm: syz-executor525 Not tainted 4.4.174+ #4 [ 50.406250] 0000000000000000 c99ca1b7ffb792c8 ffff8801d4007730 ffffffff81aad1a1 [ 50.414319] 0000000000000000 ffffea0002d9b000 ffff8800b66c51e8 0000000000000008 executing program executing program executing program executing program executing program executing program executing program [ 50.422393] 0000000000000000 ffff8801d4007768 ffffffff81490120 0000000000000000 [ 50.430418] Call Trace: [ 50.433000] [] dump_stack+0xc1/0x120 [ 50.438371] [] print_address_description+0x6f/0x21b [ 50.445052] [] kasan_report.cold+0x8c/0x2be [ 50.451039] [] ? disk_unblock_events+0x55/0x60 [ 50.457290] [] __asan_report_load8_noabort+0x14/0x20 [ 50.464091] [] disk_unblock_events+0x55/0x60 [ 50.470154] [] __blkdev_get+0x70c/0xdf0 executing program executing program executing program executing program executing program executing program executing program executing program executing program [ 50.475779] [] ? __blkdev_put+0x840/0x840 [ 50.481586] [] ? blkdev_get_block+0x80/0x80 [ 50.487566] [] ? __might_sleep+0x90/0x1a0 [ 50.493371] [] blkdev_get+0x2e8/0x920 [ 50.498833] [] ? bd_may_claim+0xd0/0xd0 [ 50.504467] [] ? bd_acquire+0x133/0x370 [ 50.510099] [] ? _raw_spin_unlock+0x2d/0x50 [ 50.516080] [] blkdev_open+0x1aa/0x250 executing program executing program executing program executing program executing program executing program executing program executing program [ 50.522675] [] do_dentry_open+0x38f/0xbd0 [ 50.528484] [] ? __inode_permission2+0x9e/0x250 [ 50.534810] [] ? blkdev_get_by_dev+0x80/0x80 [ 50.540885] [] vfs_open+0x10b/0x210 [ 50.546173] [] ? may_open.isra.0+0xe7/0x210 [ 50.552151] [] path_openat+0x136f/0x4470 [ 50.557879] [] ? kasan_kmalloc.part.0+0xc6/0xf0 [ 50.564208] [] ? may_open.isra.0+0x210/0x210 [ 50.570282] [] ? trace_hardirqs_on+0x10/0x10 executing program executing program executing program executing program executing program executing program executing program [ 50.576359] [] do_filp_open+0x1a1/0x270 [ 50.582000] [] ? user_path_mountpoint_at+0x50/0x50 [ 50.588590] [] ? __alloc_fd+0x1ea/0x490 [ 50.594226] [] ? _raw_spin_unlock+0x2d/0x50 [ 50.600209] [] do_sys_open+0x2f8/0x600 [ 50.605751] [] ? filp_open+0x70/0x70 [ 50.611122] [] ? retint_user+0x18/0x3c [ 50.616665] [] ? trace_hardirqs_on_caller+0x385/0x5a0 executing program executing program executing program executing program [ 50.623513] [] SyS_open+0x2d/0x40 [ 50.628681] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 50.635254] [ 50.636888] Allocated by task 2114: [ 50.640505] [] save_stack_trace+0x26/0x50 [ 50.646450] [] kasan_kmalloc.part.0+0x62/0xf0 [ 50.652738] [] kasan_kmalloc+0xb7/0xd0 [ 50.658426] [] kmem_cache_alloc_trace+0x123/0x2d0 [ 50.665070] [] alloc_disk_node+0x50/0x3c0 [ 50.671013] [] alloc_disk+0x1b/0x20 [ 50.676428] [] loop_add+0x380/0x830 [ 50.681844] [] loop_control_ioctl+0x215/0x2f0 [ 50.688137] [] do_vfs_ioctl+0x6e7/0xfa0 [ 50.693905] [] SyS_ioctl+0x8f/0xc0 [ 50.699246] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 50.705967] [ 50.707592] Freed by task 2114: [ 50.710868] [] save_stack_trace+0x26/0x50 [ 50.716830] [] kasan_slab_free+0xb0/0x190 [ 50.722802] [] kfree+0xf4/0x310 [ 50.727878] [] disk_release+0x255/0x330 [ 50.733640] [] device_release+0x7d/0x220 [ 50.739494] [] kobject_put+0x14c/0x260 [ 50.745173] [] put_disk+0x23/0x30 [ 50.750411] [] __blkdev_get+0x66c/0xdf0 [ 50.756175] [] blkdev_get+0x2e8/0x920 [ 50.762110] [] blkdev_open+0x1aa/0x250 [ 50.767783] [] do_dentry_open+0x38f/0xbd0 [ 50.773724] [] vfs_open+0x10b/0x210 [ 50.779135] [] path_openat+0x136f/0x4470 [ 50.784990] [] do_filp_open+0x1a1/0x270 [ 50.790754] [] do_sys_open+0x2f8/0x600 [ 50.796432] [] SyS_open+0x2d/0x40 [ 50.801670] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 50.808391] [ 50.810017] The buggy address belongs to the object at ffff8800b66c4c80 [ 50.810017] which belongs to the cache kmalloc-2048 of size 2048 [ 50.822852] The buggy address is located 1384 bytes inside of [ 50.822852] 2048-byte region [ffff8800b66c4c80, ffff8800b66c5480) [ 50.834905] The buggy address belongs to the page: [ 50.841817] ------------[ cut here ]------------ [ 50.846644] WARNING: CPU: 1 PID: 2091 at lib/list_debug.c:51 __list_del_entry_valid+0x11d/0x1a0() [ 50.855669] list_del corruption. prev->next should be ffff8800ba3d1c00, but was ffff8800b66c5480 [ 50.864723] Kernel panic - not syncing: panic_on_warn set ... [ 50.864723] [ 50.872103] CPU: 1 PID: 2091 Comm: syz-executor525 Not tainted 4.4.174+ #4 [ 50.879124] 0000000000000000 09386c02b6f76ddc ffff8800b6a4f970 ffffffff81aad1a1 [ 50.887248] ffff8800b6a4fac0 ffffffff82835ee0 ffffffff8292c140 0000000000000033 [ 50.895336] ffffffff81b0b03d ffff8800b6a4fa50 ffffffff813a48c2 0000000041b58ab3 [ 50.903428] Call Trace: [ 50.906033] [] dump_stack+0xc1/0x120 [ 50.911417] [] ? __list_del_entry_valid+0x11d/0x1a0 [ 50.918109] [] panic+0x1b9/0x37b [ 50.923139] [] ? add_taint.cold+0x16/0x16 [ 50.928952] [] ? vprintk_emit+0x248/0x820 [ 50.934773] [] ? warn_slowpath_common.cold+0x5/0x20 [ 50.941466] [] warn_slowpath_common.cold+0x20/0x20 [ 50.948064] [] warn_slowpath_fmt+0xbf/0x100 [ 50.954051] [] ? warn_slowpath_common+0x120/0x120 [ 50.960563] [] __list_del_entry_valid+0x11d/0x1a0 [ 50.967071] [] ? detach_pid+0x20/0x30 [ 50.972544] [] release_task+0xc77/0x14a0 [ 50.978274] [] ? wait_consider_task+0x16b1/0x35b0 [ 50.984786] [] wait_consider_task+0x16b1/0x35b0 [ 50.991126] [] ? do_wait+0x350/0xa00 [ 50.996592] [] ? complete_and_exit+0x40/0x40 [ 51.002668] [] do_wait+0x350/0xa00 [ 51.007889] [] ? wait_consider_task+0x35b0/0x35b0 [ 51.014403] [] SyS_wait4+0x144/0x210 [ 51.019789] [] ? SyS_waitid+0x2d0/0x2d0 [ 51.025432] [] ? kill_orphaned_pgrp+0x310/0x310 [ 51.031775] [] ? lockdep_sys_exit_thunk+0x12/0x14 [ 51.038284] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 52.140250] Shutting down cpus with NMI [ 52.144551] Kernel Offset: disabled [ 52.148273] Rebooting in 86400 seconds..