random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) ====================================================== WARNING: possible circular locking dependency detected 4.17.0-rc2+ #23 Not tainted ------------------------------------------------------ syz-executor715/4492 is trying to acquire lock: (ptrval) (sb_writers#6){.+.+}, at: file_start_write include/linux/fs.h:2718 [inline] (ptrval) (sb_writers#6){.+.+}, at: vfs_fallocate+0x5be/0x8d0 fs/open.c:318 but task is already holding lock: (ptrval) (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xac/0x560 drivers/staging/android/ashmem.c:440 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (ashmem_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16d/0x17f0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 ashmem_mmap+0x53/0x460 drivers/staging/android/ashmem.c:361 call_mmap include/linux/fs.h:1789 [inline] mmap_region+0xd13/0x1820 mm/mmap.c:1723 do_mmap+0xc79/0x11d0 mm/mmap.c:1494 do_mmap_pgoff include/linux/mm.h:2237 [inline] vm_mmap_pgoff+0x1fb/0x2a0 mm/util.c:357 ksys_mmap_pgoff+0x4c9/0x640 mm/mmap.c:1544 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline] __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&mm->mmap_sem){++++}: __might_fault+0x155/0x1e0 mm/memory.c:4555 _copy_to_user+0x30/0x110 lib/usercopy.c:25 copy_to_user include/linux/uaccess.h:155 [inline] filldir+0x1ea/0x3a0 fs/readdir.c:196 dir_emit_dot include/linux/fs.h:3378 [inline] dir_emit_dots include/linux/fs.h:3389 [inline] dcache_readdir+0x13a/0x620 fs/libfs.c:192 iterate_dir+0x4b0/0x5d0 fs/readdir.c:51 __do_sys_getdents fs/readdir.c:231 [inline] __se_sys_getdents fs/readdir.c:212 [inline] __x64_sys_getdents+0x293/0x4e0 fs/readdir.c:212 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&sb->s_type->i_mutex_key#11){++++}: down_write+0x87/0x120 kernel/locking/rwsem.c:70 inode_lock include/linux/fs.h:713 [inline] do_last fs/namei.c:3274 [inline] path_openat+0x123b/0x4e20 fs/namei.c:3501 do_filp_open+0x249/0x350 fs/namei.c:3535 do_sys_open+0x56f/0x740 fs/open.c:1093 __do_sys_open fs/open.c:1111 [inline] __se_sys_open fs/open.c:1106 [inline] __x64_sys_open+0x7e/0xc0 fs/open.c:1106 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (sb_writers#6){.+.+}: lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline] percpu_down_read include/linux/percpu-rwsem.h:59 [inline] __sb_start_write+0x1e9/0x300 fs/super.c:1385 file_start_write include/linux/fs.h:2718 [inline] vfs_fallocate+0x5be/0x8d0 fs/open.c:318 ashmem_shrink_scan+0x1f1/0x560 drivers/staging/android/ashmem.c:447 ashmem_ioctl+0x3bf/0x13a0 drivers/staging/android/ashmem.c:789 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 __do_sys_ioctl fs/ioctl.c:708 [inline] __se_sys_ioctl fs/ioctl.c:706 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: sb_writers#6 --> &mm->mmap_sem --> ashmem_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ashmem_mutex); lock(&mm->mmap_sem); lock(ashmem_mutex); lock(sb_writers#6); *** DEADLOCK *** 1 lock held by syz-executor715/4492: #0: (ptrval) (ashmem_mutex){+.+.}, at: ashmem_shrink_scan+0xac/0x560 drivers/staging/android/ashmem.c:440 stack backtrace: CPU: 1 PID: 4492 Comm: syz-executor715 Not tainted 4.17.0-rc2+ #23 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 print_circular_bug.isra.36.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1223 check_prev_add kernel/locking/lockdep.c:1863 [inline] check_prevs_add kernel/locking/lockdep.c:1976 [inline] validate_chain kernel/locking/lockdep.c:2417 [inline] __lock_acquire+0x343e/0x5140 kernel/locking/lockdep.c:3431 lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline] percpu_down_read include/linux/percpu-rwsem.h:59 [inline] __sb_start_write+0x1e9/0x300 fs/super.c:1385 file_start_write include/linux/fs.h:2718 [inline] vfs_fallocate+0x5be/0x8d0 fs/open.c:318 ashmem_shrink_scan+0x1f1/0x560 drivers/staging/android/ashmem.c:447 ashmem_ioctl+0x3bf/0x13a0 drivers/staging/android/ashmem.c:789 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 __do_sys_ioctl fs/ioctl.c:708 [inline] __se_sys_ioctl fs/ioctl.c:706 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x440179 RSP: 002b:00007ffc165d4a28 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 6873612f7665642f RCX: 0000000000440179 RDX: 0000000000000000 RSI: 000000000000770a RDI: 0000000000000004 RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000004 R11: 0000000000000217 R12: 00000000004016a0 R13: 0000000000401730 R14: 0000000000000000 R15: 0000000000000000 random: crng init done