syzbot

============================================
WARNING: possible recursive locking detected
4.19.211-syzkaller #0 Not tainted
--------------------------------------------
syz-executor301/8133 is trying to acquire lock:
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: __blocking_notifier_call_chain kernel/notifier.c:304 [inline]
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: blocking_notifier_call_chain kernel/notifier.c:328 [inline]
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: blocking_notifier_call_chain+0x6f/0xa0 kernel/notifier.c:325

but task is already holding lock:
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: __blocking_notifier_call_chain kernel/notifier.c:304 [inline]
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: blocking_notifier_call_chain kernel/notifier.c:328 [inline]
0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: blocking_notifier_call_chain+0x6f/0xa0 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-executor301/8133:
 #0: 00000000c985598e (console_lock){+.+.}, at: do_fb_ioctl+0x772/0xb50 drivers/video/fbdev/core/fbmem.c:1210
 #1: 00000000d3bb56cf (&fb_info->lock){+.+.}, at: lock_fb_info drivers/video/fbdev/core/fbmem.c:81 [inline]
 #1: 00000000d3bb56cf (&fb_info->lock){+.+.}, at: do_fb_ioctl+0x77c/0xb50 drivers/video/fbdev/core/fbmem.c:1211
 #2: 0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: __blocking_notifier_call_chain kernel/notifier.c:316 [inline]
 #2: 0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: __blocking_notifier_call_chain kernel/notifier.c:304 [inline]
 #2: 0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: blocking_notifier_call_chain kernel/notifier.c:328 [inline]
 #2: 0000000049dd2a93 ((fb_notifier_list).rwsem){++++}, at: blocking_notifier_call_chain+0x6f/0xa0 kernel/notifier.c:325

stack backtrace:
CPU: 0 PID: 8133 Comm: syz-executor301 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_deadlock_bug kernel/locking/lockdep.c:1764 [inline]
 check_deadlock kernel/locking/lockdep.c:1808 [inline]
 validate_chain kernel/locking/lockdep.c:2404 [inline]
 __lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 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+0x6f/0xa0 kernel/notifier.c:325
 fb_set_var+0xd9a/0xf90 drivers/video/fbdev/core/fbmem.c:1052
 fbcon_switch+0x425/0x1ba0 drivers/video/fbdev/core/fbcon.c:2088
 redraw_screen+0x37d/0x870 drivers/tty/vt/vt.c:1015
 fbcon_blank+0xae6/0xec0 drivers/video/fbdev/core/fbcon.c:2226
 do_unblank_screen+0x241/0x610 drivers/tty/vt/vt.c:4294
 fbcon_fb_blanked drivers/video/fbdev/core/fbcon.c:2973 [inline]
 fbcon_event_notify+0x1a3a/0x1d80 drivers/video/fbdev/core/fbcon.c:3091
 notifier_call_chain+0xc0/0x230 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+0x85/0xa0 kernel/notifier.c:325
 fb_blank+0x195/0x1d0 drivers/video/fbdev/core/fbmem.c:1080
 do_fb_ioctl+0x7ec/0xb50 drivers/video/fbdev/core/fbmem.c:1216
 fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1240
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f36d2d29269
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe8aaad968 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000000f4240 RCX: 00007f36d2d29269
RDX: 0000000000000000 RSI: 0000000000004611 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
R10: 00007ffe8aaad3e0 R11: 0000000000000246 R12: 000000000000a22c
R13: 00007ffe8aaad97c R14: 00007ffe8aaad990 R15: 00007ffe8aaad980