============================================ WARNING: possible recursive locking detected 4.14.280-syzkaller #0 Not tainted -------------------------------------------- syz-executor337/7995 is trying to acquire lock: ((fb_notifier_list).rwsem){++++}, at: [] __blocking_notifier_call_chain kernel/notifier.c:316 [inline] ((fb_notifier_list).rwsem){++++}, at: [] __blocking_notifier_call_chain kernel/notifier.c:304 [inline] ((fb_notifier_list).rwsem){++++}, at: [] blocking_notifier_call_chain kernel/notifier.c:328 [inline] ((fb_notifier_list).rwsem){++++}, at: [] blocking_notifier_call_chain+0x63/0x90 kernel/notifier.c:325 but task is already holding lock: ((fb_notifier_list).rwsem){++++}, at: [] __blocking_notifier_call_chain kernel/notifier.c:316 [inline] ((fb_notifier_list).rwsem){++++}, at: [] __blocking_notifier_call_chain kernel/notifier.c:304 [inline] ((fb_notifier_list).rwsem){++++}, at: [] blocking_notifier_call_chain kernel/notifier.c:328 [inline] ((fb_notifier_list).rwsem){++++}, at: [] blocking_notifier_call_chain+0x63/0x90 kernel/notifier.c:325 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock((fb_notifier_list).rwsem); lock((fb_notifier_list).rwsem); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by syz-executor337/7995: #0: (console_lock){+.+.}, at: [] do_fb_ioctl+0x81a/0xa70 drivers/video/fbdev/core/fbmem.c:1223 #1: (&fb_info->lock){+.+.}, at: [] lock_fb_info drivers/video/fbdev/core/fbmem.c:82 [inline] #1: (&fb_info->lock){+.+.}, at: [] do_fb_ioctl+0x824/0xa70 drivers/video/fbdev/core/fbmem.c:1224 #2: ((fb_notifier_list).rwsem){++++}, at: [] __blocking_notifier_call_chain kernel/notifier.c:316 [inline] #2: ((fb_notifier_list).rwsem){++++}, at: [] __blocking_notifier_call_chain kernel/notifier.c:304 [inline] #2: ((fb_notifier_list).rwsem){++++}, at: [] blocking_notifier_call_chain kernel/notifier.c:328 [inline] #2: ((fb_notifier_list).rwsem){++++}, at: [] blocking_notifier_call_chain+0x63/0x90 kernel/notifier.c:325 stack backtrace: CPU: 0 PID: 7995 Comm: syz-executor337 Not tainted 4.14.280-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x281 lib/dump_stack.c:58 print_deadlock_bug kernel/locking/lockdep.c:1800 [inline] check_deadlock kernel/locking/lockdep.c:1847 [inline] validate_chain kernel/locking/lockdep.c:2448 [inline] __lock_acquire.cold+0x180/0x97c kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 down_read+0x36/0x80 kernel/locking/rwsem.c:24 __blocking_notifier_call_chain kernel/notifier.c:316 [inline] __blocking_notifier_call_chain kernel/notifier.c:304 [inline] blocking_notifier_call_chain kernel/notifier.c:328 [inline] blocking_notifier_call_chain+0x63/0x90 kernel/notifier.c:325 fb_set_var+0xbc8/0xdc0 drivers/video/fbdev/core/fbmem.c:1065 fbcon_switch+0x3d9/0x19e0 drivers/video/fbdev/core/fbcon.c:2066 redraw_screen+0x32c/0x790 drivers/tty/vt/vt.c:689 fbcon_blank+0x986/0xd50 drivers/video/fbdev/core/fbcon.c:2204 do_unblank_screen+0x1fd/0x4e0 drivers/tty/vt/vt.c:3954 fbcon_fb_blanked drivers/video/fbdev/core/fbcon.c:2928 [inline] fbcon_event_notify+0x1445/0x1760 drivers/video/fbdev/core/fbcon.c:3046 notifier_call_chain+0x108/0x1a0 kernel/notifier.c:93 __blocking_notifier_call_chain kernel/notifier.c:317 [inline] __blocking_notifier_call_chain kernel/notifier.c:304 [inline] blocking_notifier_call_chain kernel/notifier.c:328 [inline] blocking_notifier_call_chain+0x79/0x90 kernel/notifier.c:325 fb_blank+0x14c/0x190 drivers/video/fbdev/core/fbmem.c:1093 do_fb_ioctl+0x894/0xa70 drivers/video/fbdev/core/fbmem.c:1229 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1253 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x7fd3a6027239 RSP: 002b:00007ffe8a0162f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fd3a6027239 RDX: 0000000000000000 RSI: 0000000000004611 RDI: 0000000000000005 RBP: 00007fd3a5feb220 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd3a5