INFO: task hung in lock_fb_info

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 98db2bf2 Linux 4.14.171
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13507a29e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=365f8162d5a0794b
dashboard link: https://syzkaller.appspot.com/bug?extid=8f1f5cf18a9934bcb873
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8f1f5c...@syzkaller.appspotmail.com

Invalid option length (64860) for dns_resolver key
Invalid option length (748) for dns_resolver key
Invalid option length (748) for dns_resolver key
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
INFO: task syz-executor.4:16380 blocked for more than 140 seconds.
Not tainted 4.14.171-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4 D29760 16380 7262 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
lock_fb_info+0x1f/0x80 drivers/video/fbdev/core/fbmem.c:81
do_fb_ioctl+0x57b/0x940 drivers/video/fbdev/core/fbmem.c:1150
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1242
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007f64e850cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f64e850d6d4 RCX: 000000000045c449
RDX: 0000000020000140 RSI: 0000000000004604 RDI: 0000000000000003
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002e8 R14: 00000000004c4fd8 R15: 000000000076bfcc
INFO: task syz-executor.0:16378 blocked for more than 140 seconds.
Not tainted 4.14.171-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0 D29488 16378 7257 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
chrdev_open+0x207/0x590 fs/char_dev.c:423
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3428 [inline]
path_openat+0x917/0x3e50 fs/namei.c:3569
do_filp_open+0x18e/0x250 fs/namei.c:3603
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_openat fs/open.c:1111 [inline]
SyS_openat+0x30/0x40 fs/open.c:1105
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007f2119bcec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2119bcf6d4 RCX: 000000000045c449
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000799 R14: 00000000004ca0ae R15: 000000000076bf2c
INFO: task syz-executor.0:16383 blocked for more than 140 seconds.
Not tainted 4.14.171-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0 D27776 16383 7257 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
chrdev_open+0x207/0x590 fs/char_dev.c:423
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3428 [inline]
path_openat+0x917/0x3e50 fs/namei.c:3569
do_filp_open+0x18e/0x250 fs/namei.c:3603
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_openat fs/open.c:1111 [inline]
SyS_openat+0x30/0x40 fs/open.c:1105
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007f2119badc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f2119bae6d4 RCX: 000000000045c449
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000799 R14: 00000000004ca0ae R15: 000000000076bfcc
INFO: task syz-executor.3:16381 blocked for more than 140 seconds.
Not tainted 4.14.171-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3 D29488 16381 7258 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
chrdev_open+0x207/0x590 fs/char_dev.c:423
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3428 [inline]
path_openat+0x917/0x3e50 fs/namei.c:3569
do_filp_open+0x18e/0x250 fs/namei.c:3603
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_openat fs/open.c:1111 [inline]
SyS_openat+0x30/0x40 fs/open.c:1105
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007f4cac204c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4cac2056d4 RCX: 000000000045c449
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000799 R14: 00000000004ca0ae R15: 000000000076bf2c
INFO: task syz-executor.3:16386 blocked for more than 140 seconds.
Not tainted 4.14.171-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3 D29488 16386 7258 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
chrdev_open+0x207/0x590 fs/char_dev.c:423
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3428 [inline]
path_openat+0x917/0x3e50 fs/namei.c:3569
do_filp_open+0x18e/0x250 fs/namei.c:3603
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_openat fs/open.c:1111 [inline]
SyS_openat+0x30/0x40 fs/open.c:1105
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007f4cac1e3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4cac1e46d4 RCX: 000000000045c449
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000076bfc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000799 R14: 00000000004ca0ae R15: 000000000076bfcc
INFO: task syz-executor.1:16392 blocked for more than 140 seconds.
Not tainted 4.14.171-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D28704 16392 7259 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3384
schedule+0x92/0x1c0 kernel/sched/core.c:3428
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x73c/0x1470 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
chrdev_open+0x207/0x590 fs/char_dev.c:423
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3428 [inline]
path_openat+0x917/0x3e50 fs/namei.c:3569
do_filp_open+0x18e/0x250 fs/namei.c:3603
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_openat fs/open.c:1111 [inline]
SyS_openat+0x30/0x40 fs/open.c:1105
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007fcab792bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fcab792c6d4 RCX: 000000000045c449
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000799 R14: 00000000004ca0ae R15: 000000000076bf2c

Showing all locks held in the system:
1 lock held by khungtaskd/1058:
#0: (tasklist_lock){.+.+}, at: [<ffffffff81484048>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4544
1 lock held by rsyslogd/7090:
#0: (&f->f_pos_lock){+.+.}, at: [<ffffffff8195e7ab>] __fdget_pos+0xab/0xd0 fs/file.c:769
2 locks held by getty/7211:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
2 locks held by getty/7212:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
2 locks held by getty/7213:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
2 locks held by getty/7214:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
2 locks held by getty/7215:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
2 locks held by getty/7216:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
2 locks held by getty/7217:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff8668c3a3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff834bd4a6>] n_tty_read+0x1e6/0x17d0 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.4/16380:
#0: (&fb_info->lock){+.+.}, at: [<ffffffff83275b7f>] lock_fb_info+0x1f/0x80 drivers/video/fbdev/core/fbmem.c:81
1 lock held by syz-executor.0/16378:
#0: (&fb_info->lock){+.+.}, at: [<ffffffff83279cc7>] fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
1 lock held by syz-executor.0/16383:
#0: (&fb_info->lock){+.+.}, at: [<ffffffff83279cc7>] fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
1 lock held by syz-executor.3/16381:
#0: (&fb_info->lock){+.+.}, at: [<ffffffff83279cc7>] fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
1 lock held by syz-executor.3/16386:
#0: (&fb_info->lock){+.+.}, at: [<ffffffff83279cc7>] fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468
1 lock held by syz-executor.1/16392:
#0: (&fb_info->lock){+.+.}, at: [<ffffffff83279cc7>] fb_open+0xb7/0x420 drivers/video/fbdev/core/fbmem.c:1468

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

NMI backtrace for cpu 0
CPU: 0 PID: 1058 Comm: khungtaskd Not tainted 4.14.171-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+0x142/0x197 lib/dump_stack.c:58
nmi_cpu_backtrace.cold+0x57/0x94 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x141/0x189 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x5e7/0xb90 kernel/hung_task.c:274
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 16372 Comm: syz-executor.4 Not tainted 4.14.171-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888061c6a540 task.stack: ffff888051c70000
RIP: 0010:__sanitizer_cov_trace_pc+0x45/0x60 kernel/kcov.c:88
RSP: 0018:ffff888051c77260 EFLAGS: 00000216
RAX: 0000000000040000 RBX: ffff8880000a0280 RCX: ffffc90009c4b000
RDX: 0000000000040000 RSI: ffffffff832ba571 RDI: 0000000000000040
RBP: ffff888051c77260 R08: 0000000000001400 R09: 0000000000000040
R10: ffffed1014bfd37b R11: ffff8880a5fe9bdf R12: 0000000000000000
R13: 0000000000000000 R14: ffff8880000a0280 R15: 0000000000000000
FS: 00007f64e852e700(0000) GS:ffff8880aed00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c42ee2cb78 CR3: 000000009f655000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__writeq arch/x86/include/asm/io.h:100 [inline]
bitfill_aligned drivers/video/fbdev/core/cfbfillrect.c:50 [inline]
bitfill_aligned+0x91/0x190 drivers/video/fbdev/core/cfbfillrect.c:35
cfb_fillrect+0x3d0/0x720 drivers/video/fbdev/core/cfbfillrect.c:327
vga16fb_fillrect+0x618/0x1880 drivers/video/fbdev/vga16fb.c:951
bit_clear_margins+0x2d5/0x4f0 drivers/video/fbdev/core/bitblit.c:232
fbcon_clear_margins+0x292/0x320 drivers/video/fbdev/core/fbcon.c:1317
fbcon_switch+0xd38/0x1820 drivers/video/fbdev/core/fbcon.c:2299
redraw_screen+0x335/0x7c0 drivers/tty/vt/vt.c:688
fbcon_modechanged+0x59e/0x880 drivers/video/fbdev/core/fbcon.c:2946
fbcon_event_notify+0x11f/0x17af drivers/video/fbdev/core/fbcon.c:3299
notifier_call_chain+0x111/0x1b0 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+0x80/0xa0 kernel/notifier.c:325
fb_notifier_call_chain+0x25/0x30 drivers/video/fbdev/core/fb_notify.c:45
fb_set_var+0xb09/0xcf0 drivers/video/fbdev/core/fbmem.c:1054
do_fb_ioctl+0x3cc/0x940 drivers/video/fbdev/core/fbmem.c:1127
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1242
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c449
RSP: 002b:00007f64e852dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f64e852e6d4 RCX: 000000000045c449
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002ef R14: 00000000004c5076 R15: 000000000076bf2c
Code: 00 75 0b 8b 90 50 13 00 00 83 fa 01 74 01 c3 55 48 89 e5 48 8b 75 08 48 8b 88 58 13 00 00 8b 80 54 13 00 00 48 8b 11 48 83 c2 01 <48> 39 d0 76 07 48 89 34 d1 48 89 11 5d c3 0f 1f 00 66 2e 0f 1f


---
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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.