[....] Starting enhanced syslogd: rsyslogd[ 14.087898] audit: type=1400 audit(1539112748.257:4): avc: denied { syslog } for pid=1922 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[ ok 8[?25h[?0c. [....] Starting periodic command scheduler: cron[?25l[?1c7[ ok 8[?25h[?0c. Starting mcstransd: [....] Starting file context maintaining daemon: restorecond[?25l[?1c7[ ok 8[?25h[?0c. [....] Starting OpenBSD Secure Shell server: sshd[?25l[?1c7[ ok 8[?25h[?0c. Debian GNU/Linux 7 syzkaller ttyS0 Warning: Permanently added '10.128.0.92' (ECDSA) to the list of known hosts. executing program executing program executing program executing program executing program syzkaller login: [ 30.698061] [ 30.699776] ====================================================== [ 30.706087] [ INFO: possible circular locking dependency detected ] [ 30.712502] 4.4.159+ #108 Not tainted [ 30.716278] ------------------------------------------------------- [ 30.722667] syz-executor122/2096 is trying to acquire lock: [ 30.728360] (&sig->cred_guard_mutex){+.+.+.}, at: [] lock_trace+0x44/0xc0 [ 30.737421] [ 30.737421] but task is already holding lock: [ 30.743376] (&p->lock){+.+.+.}, at: [] seq_read+0xdd/0x12b0 [ 30.751210] [ 30.751210] which lock already depends on the new lock. [ 30.751210] [ 30.759507] [ 30.759507] the existing dependency chain (in reverse order) is: [ 30.767106] -> #7 (&p->lock){+.+.+.}: [ 30.771543] [] lock_acquire+0x15e/0x450 [ 30.777793] [] mutex_lock_nested+0xbb/0x8d0 [ 30.784399] [] seq_read+0xdd/0x12b0 [ 30.790415] [] do_loop_readv_writev+0x148/0x1e0 [ 30.797492] [] do_readv_writev+0x581/0x6f0 [ 30.803997] [] vfs_readv+0x78/0xb0 [ 30.809846] [] default_file_splice_read+0x50f/0x8f0 [ 30.817131] [] do_splice_to+0xf7/0x140 [ 30.823536] [] splice_direct_to_actor+0x242/0x830 [ 30.830663] [] do_splice_direct+0x1a3/0x270 [ 30.837278] [] do_sendfile+0x4e4/0xb80 [ 30.843481] [] SyS_sendfile64+0xc3/0x150 [ 30.849818] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 30.857141] -> #6 (sb_writers#4){.+.+.+}: [ 30.862065] [] lock_acquire+0x15e/0x450 [ 30.868334] [] __sb_start_write+0x1ae/0x310 [ 30.875080] [] ext4_lazyinit_thread+0x1a7/0x750 [ 30.882057] [] kthread+0x268/0x300 [ 30.887928] [] ret_from_fork+0x55/0x80 [ 30.894108] -> #5 (&eli->li_list_mtx){+.+...}: [ 30.899319] [] lock_acquire+0x15e/0x450 [ 30.905569] [] mutex_lock_nested+0xbb/0x8d0 [ 30.912191] [] ext4_register_li_request+0x304/0x7a0 [ 30.919640] [] ext4_remount+0x1368/0x1bb0 [ 30.926085] [] do_remount_sb2+0x428/0x7d0 [ 30.932504] [] do_mount+0x101e/0x2a10 [ 30.938588] [] SyS_mount+0x191/0x1c0 [ 30.944574] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 30.951784] -> #4 (&ext4_li_mtx){+.+.+.}: [ 30.956559] [] lock_acquire+0x15e/0x450 [ 30.962953] [] mutex_lock_nested+0xbb/0x8d0 [ 30.969551] [] ext4_register_li_request+0x87/0x7a0 [ 30.976782] [] ext4_remount+0x1368/0x1bb0 [ 30.983207] [] do_remount_sb2+0x428/0x7d0 [ 30.989649] [] do_mount+0x101e/0x2a10 [ 30.995712] [] SyS_mount+0x191/0x1c0 [ 31.001835] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 31.009054] -> #3 (&type->s_umount_key#34){++++++}: [ 31.014855] [] lock_acquire+0x15e/0x450 [ 31.021194] [] down_read+0x42/0x60 [ 31.027133] [] iterate_supers+0xe1/0x260 [ 31.033492] [] selinux_complete_init+0x2f/0x31 [ 31.040351] [] security_load_policy+0x886/0x9b0 [ 31.047310] [] sel_write_load+0x191/0xfc0 [ 31.053729] [] __vfs_write+0x11c/0x3e0 [ 31.059948] [] vfs_write+0x17e/0x4e0 [ 31.066006] [] SyS_write+0xd9/0x1c0 [ 31.071901] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 31.079121] -> #2 (sel_mutex){+.+.+.}: [ 31.083652] [] lock_acquire+0x15e/0x450 [ 31.089908] [] mutex_lock_nested+0xbb/0x8d0 [ 31.096594] [] sel_commit_bools_write+0x87/0x250 [ 31.103620] [] __vfs_write+0x11c/0x3e0 [ 31.109778] [] __kernel_write+0x10a/0x350 [ 31.116197] [] write_pipe_buf+0x15d/0x1f0 [ 31.122614] [] __splice_from_pipe+0x364/0x790 [ 31.129375] [] splice_from_pipe+0xf9/0x170 [ 31.135882] [] default_file_splice_write+0x3c/0x80 [ 31.143089] [] SyS_splice+0xde1/0x1430 [ 31.149242] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 31.156472] -> #1 (&pipe->mutex/1){+.+.+.}: [ 31.161550] [] lock_acquire+0x15e/0x450 [ 31.167804] [] mutex_lock_nested+0xbb/0x8d0 [ 31.174406] [] fifo_open+0x15c/0x9e0 [ 31.180390] [] do_dentry_open+0x38d/0xbd0 [ 31.186917] [] vfs_open+0x12a/0x210 [ 31.192824] [] path_openat+0x50c/0x39a0 [ 31.199066] [] do_filp_open+0x197/0x270 [ 31.205321] [] do_open_execat+0x10f/0x6f0 [ 31.211749] [] do_execveat_common.isra.14+0x6a1/0x1f00 [ 31.219288] [] SyS_execve+0x42/0x50 [ 31.225229] [] return_from_execve+0x0/0x23 [ 31.231877] -> #0 (&sig->cred_guard_mutex){+.+.+.}: [ 31.237641] [] __lock_acquire+0x3e6c/0x5f10 [ 31.244246] [] lock_acquire+0x15e/0x450 [ 31.250501] [] mutex_lock_killable_nested+0xcc/0xa10 [ 31.257880] [] lock_trace+0x44/0xc0 [ 31.263785] [] proc_pid_personality+0x1c/0xc0 [ 31.270563] [] proc_single_show+0xfd/0x170 [ 31.277102] [] seq_read+0x4b6/0x12b0 [ 31.283203] [] do_loop_readv_writev+0x148/0x1e0 [ 31.290233] [] do_readv_writev+0x581/0x6f0 [ 31.296746] [] vfs_readv+0x78/0xb0 [ 31.302685] [] default_file_splice_read+0x50f/0x8f0 [ 31.309987] [] do_splice_to+0xf7/0x140 [ 31.316146] [] splice_direct_to_actor+0x242/0x830 [ 31.323265] [] do_splice_direct+0x1a3/0x270 [ 31.329869] [] do_sendfile+0x4e4/0xb80 [ 31.336020] [] SyS_sendfile64+0xc3/0x150 [ 31.342348] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 31.349551] [ 31.349551] other info that might help us debug this: [ 31.349551] [ 31.357666] Chain exists of: &sig->cred_guard_mutex --> sb_writers#4 --> &p->lock [ 31.366571] Possible unsafe locking scenario: [ 31.366571] [ 31.372600] CPU0 CPU1 [ 31.377237] ---- ---- [ 31.381874] lock(&p->lock); [ 31.385207] lock(sb_writers#4); [ 31.391604] lock(&p->lock); [ 31.397441] lock(&sig->cred_guard_mutex); [ 31.401973] [ 31.401973] *** DEADLOCK *** [ 31.401973] [ 31.408027] 1 lock held by syz-executor122/2096: [ 31.412822] #0: (&p->lock){+.+.+.}, at: [] seq_read+0xdd/0x12b0 [ 31.421364] [ 31.421364] stack backtrace: [ 31.425839] CPU: 1 PID: 2096 Comm: syz-executor122 Not tainted 4.4.159+ #108 [ 31.432999] 0000000000000000 6addc59d46797ecf ffff8800b6666f28 ffffffff81a994bd [ 31.441073] ffffffff83ab46a0 ffffffff83ab04d0 ffffffff83aaeb80 ffff8801d54467e8 [ 31.449064] ffff8801d5445f00 ffff8800b6666f70 ffffffff813a84ea 0000000000000001 [ 31.457102] Call Trace: [ 31.459670] [] dump_stack+0xc1/0x124 [ 31.465027] [] print_circular_bug.cold.34+0x2f7/0x432 [ 31.471847] [] __lock_acquire+0x3e6c/0x5f10 [ 31.477797] [] ? trace_hardirqs_on+0x10/0x10 [ 31.483838] [] ? kasan_kmalloc.part.1+0xc9/0xf0 [ 31.490134] [] ? do_readv_writev+0x581/0x6f0 [ 31.496228] [] ? default_file_splice_read+0x50f/0x8f0 [ 31.503055] [] ? splice_direct_to_actor+0x242/0x830 [ 31.509696] [] ? do_splice_direct+0x1a3/0x270 [ 31.515821] [] lock_acquire+0x15e/0x450 [ 31.521433] [] ? lock_trace+0x44/0xc0 [ 31.526874] [] mutex_lock_killable_nested+0xcc/0xa10 [ 31.533657] [] ? lock_trace+0x44/0xc0 [ 31.539091] [] ? lock_trace+0x44/0xc0 [ 31.544628] [] ? _mutex_lock_nest_lock+0x8d0/0x8d0 [ 31.551190] [] ? check_preemption_disabled+0x3b/0x170 [ 31.558006] [] lock_trace+0x44/0xc0 [ 31.563416] [] proc_pid_personality+0x1c/0xc0 [ 31.569540] [] proc_single_show+0xfd/0x170 [ 31.575408] [] seq_read+0x4b6/0x12b0 [ 31.580750] [] ? seq_lseek+0x3c0/0x3c0 [ 31.586266] [] ? __fsnotify_update_child_dentry_flags.part.0+0x300/0x300 [ 31.594762] [] ? avc_policy_seqno+0x9/0x20 [ 31.600626] [] do_loop_readv_writev+0x148/0x1e0 [ 31.606926] [] ? security_file_permission+0x8f/0x1e0 [ 31.613775] [] ? seq_lseek+0x3c0/0x3c0 [ 31.619293] [] ? seq_lseek+0x3c0/0x3c0 [ 31.624841] [] do_readv_writev+0x581/0x6f0 [ 31.630719] [] ? vfs_write+0x4e0/0x4e0 [ 31.636430] [] ? __alloc_pages_direct_compact+0x220/0x220 [ 31.643607] [] ? get_page_from_freelist+0x6cb/0x1f60 [ 31.650344] [] ? kasan_unpoison_shadow+0x35/0x50 [ 31.656727] [] ? kasan_alloc_pages+0x38/0x40 [ 31.662884] [] ? get_page_from_freelist+0xefd/0x1f60 [ 31.669623] [] ? trace_hardirqs_on_caller+0x38b/0x590 [ 31.676446] [] vfs_readv+0x78/0xb0 [ 31.681751] [] default_file_splice_read+0x50f/0x8f0 [ 31.688556] [] ? generic_file_splice_read+0x1c0/0x1c0 [ 31.695399] [] ? is_module_text_address+0x2a/0x50 [ 31.701875] [] ? __kernel_text_address+0x6b/0xa0 [ 31.708433] [] ? print_context_stack+0x4e/0xe0 [ 31.714656] [] ? page_cache_pipe_buf_release+0x70/0x70 [ 31.721562] [] ? dump_trace+0x184/0x360 [ 31.727293] [] ? save_stack_trace+0x26/0x50 [ 31.733277] [] ? kasan_kmalloc.part.1+0x62/0xf0 [ 31.739595] [] ? kasan_kmalloc+0xaf/0xc0 [ 31.745279] [] ? __kmalloc+0x13d/0x330 [ 31.750809] [] ? alloc_pipe_info+0x340/0x410 [ 31.756844] [] ? splice_direct_to_actor+0x661/0x830 [ 31.763490] [] ? do_splice_direct+0x1a3/0x270 [ 31.769612] [] ? do_sendfile+0x4e4/0xb80 [ 31.775452] [] ? SyS_sendfile64+0xc3/0x150 [ 31.781339] [] ? entry_SYSCALL_64_fastpath+0x1e/0x9a [ 31.788191] [] ? new_slab+0x2d3/0x380 [ 31.793618] [] ? fsnotify+0x866/0x10c0 [ 31.799130] [] ? rw_verify_area+0x100/0x2f0 [ 31.805099] [] ? generic_file_splice_read+0x1c0/0x1c0 [ 31.812027] [] do_splice_to+0xf7/0x140 [ 31.817545] [] splice_direct_to_actor+0x242/0x830 [ 31.824019] [] ? inode_has_perm.isra.20+0x10c/0x160 [ 31.830658] [] ? pipe_to_sendpage+0x330/0x330 [ 31.836777] [] ? do_splice_to+0x140/0x140 [ 31.842553] [] ? security_file_permission+0x8f/0x1e0 [ 31.849282] [] ? rw_verify_area+0x100/0x2f0 [ 31.855519] [] do_splice_direct+0x1a3/0x270 [ 31.861474] [] ? splice_direct_to_actor+0x830/0x830 [ 31.868119] [] ? rw_verify_area+0x100/0x2f0 [ 31.874165] [] do_sendfile+0x4e4/0xb80 [ 31.879753] [] ? __compat_sys_pwritev64+0x170/0x170 [ 31.886404] [] ? __might_fault+0x114/0x1d0 [ 31.892261] [] SyS_sendfile64+0xc3/0x150 executing program executing program [ 31.897943] [] ? SyS_sendfile+0x160/0x160 [ 31.903716] [] ? lockdep_sys_exit_thunk+0x12/0x14 [ 31.910185] [] entry_SYSCALL_64_fastpath+0x1e/0x9a executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program 00000000 executing program executing program 00000000 executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program 00000000 executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program 00000000 executing program 00000000 executing program 00000000 executing program executing program 00000000 executing program executing program 00000000 executing program executing program 00000000 executing program executing program 00000000 executing program executing program executing program 00000000 executing program 00000000 executing program executing program 00000000 executing program executing program executing program executing program 00000000 executing program 00000000 executing program executing program 00000000 executing program executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program executing program executing program 00000000 executing program executing program 00000000 executing program executing program executing program executing program 00000000 executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program executing program 00000000 executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program executing program 00000000 executing program executing program executing program executing program