syzbot

INFO: task syz-executor.5:2641 blocked for more than 143 seconds.
      Not tainted 5.9.0-rc6-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.5  state:D stack:28728 pid: 2641 ppid:  6879 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3778 [inline]
 __schedule+0xec9/0x2280 kernel/sched/core.c:4527
 schedule+0xd0/0x2a0 kernel/sched/core.c:4602
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4661
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x3e2/0x10e0 kernel/locking/mutex.c:1103
 lock_fb_info include/linux/fb.h:636 [inline]
 fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1414
 chrdev_open+0x266/0x770 fs/char_dev.c:414
 do_dentry_open+0x4b9/0x11b0 fs/open.c:817
 do_open fs/namei.c:3251 [inline]
 path_openat+0x1b9a/0x2730 fs/namei.c:3368
 do_filp_open+0x17e/0x3c0 fs/namei.c:3395
 do_sys_openat2+0x16d/0x420 fs/open.c:1168
 do_sys_open fs/open.c:1184 [inline]
 __do_sys_openat fs/open.c:1200 [inline]
 __se_sys_openat fs/open.c:1195 [inline]
 __x64_sys_openat+0x13f/0x1f0 fs/open.c:1195
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e179
Code: Bad RIP value.
RSP: 002b:00007fb6a4ccdc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000000227c0 RCX: 000000000045e179
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000118d030 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cff4
R13: 00007ffd1314445f R14: 00007fb6a4cce9c0 R15: 000000000118cff4

Showing all locks held in the system:
1 lock held by khungtaskd/1174:
 #0: ffffffff8a067f00 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5852
1 lock held by in:imklog/6546:
 #0: ffff8880a24fb670 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:930
2 locks held by syz-executor.5/2612:
1 lock held by syz-executor.5/2641:
 #0: ffff888218b57078 (&fb_info->lock){+.+.}-{3:3}, at: lock_fb_info include/linux/fb.h:636 [inline]
 #0: ffff888218b57078 (&fb_info->lock){+.+.}-{3:3}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1414

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1174 Comm: khungtaskd Not tainted 5.9.0-rc6-syzkaller #0
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+0x198/0x1fd lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
 watchdog+0xd7d/0x1000 kernel/hung_task.c:295
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 2612 Comm: syz-executor.5 Not tainted 5.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__sanitizer_cov_trace_pc+0x49/0x60 kernel/kcov.c:203
Code: 35 8b 82 2c 14 00 00 85 c0 74 2b 8b 82 08 14 00 00 83 f8 02 75 20 48 8b 8a 10 14 00 00 8b 92 0c 14 00 00 48 8b 01 48 83 c0 01 <48> 39 c2 76 07 48 89 34 c1 48 89 01 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 0018:ffffc90016baf848 EFLAGS: 00000216
RAX: 0000000000040000 RBX: 0000000000000050 RCX: ffffc90013226000
RDX: 0000000000040000 RSI: ffffffff83f00a60 RDI: 0000000000000004
RBP: 0000000000000029 R08: 0000000000000001 R09: ffff888218b5409f
R10: 0000000000000050 R11: 0000000000000000 R12: ffff8880000a0029
R13: ffff8880000a0000 R14: 0000000000000000 R15: 00000000737e1c89
FS:  00007fb6a4cef700(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055be4f14d970 CR3: 0000000031d4f000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 writeb arch/x86/include/asm/io.h:65 [inline]
 vga16fb_fillrect+0x9c0/0x193b drivers/video/fbdev/vga16fb.c:923
 bit_clear_margins+0x2d5/0x4b0 drivers/video/fbdev/core/bitblit.c:232
 fbcon_clear_margins+0x1f1/0x280 drivers/video/fbdev/core/fbcon.c:1327
 fbcon_switch+0xafe/0x16b0 drivers/video/fbdev/core/fbcon.c:2191
 redraw_screen+0x2b9/0x790 drivers/tty/vt/vt.c:1020
 fbcon_modechanged+0x593/0x6d0 drivers/video/fbdev/core/fbcon.c:2702
 fbcon_update_vcs+0x3a/0x50 drivers/video/fbdev/core/fbcon.c:2747
 do_fb_ioctl+0x62e/0x690 drivers/video/fbdev/core/fbmem.c:1106
 fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1181
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e179
Code: 3d b2 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 0b b2 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb6a4ceec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000e280 RCX: 000000000045e179
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffd1314445f R14: 00007fb6a4cef9c0 R15: 000000000118cf4c