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Date
SubjectINFO: task hung in fb_release
From
Hello,

syzbot found the following crash on:

HEAD commit: c6017471 Merge tag 'xfs-5.5-fixes-2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=127d0799e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7f6119e2e3675a73
dashboard link: https://syzkaller.appspot.com/bug?extid=d130c4a0890561cfac5b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=169b1925e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12b9623ee00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d130c4a0890561cfac5b@syzkaller.appspotmail.com

INFO: task syz-executor500:14993 blocked for more than 143 seconds.
Not tainted 5.5.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor500 D28160 14993 9196 0x00004004
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x934/0x1f90 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:4214
__mutex_lock_common kernel/locking/mutex.c:1033 [inline]
__mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1103
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1118
lock_fb_info include/linux/fb.h:637 [inline]
fb_release+0x55/0x150 drivers/video/fbdev/core/fbmem.c:1435
__fput+0x2ff/0x890 fs/file_table.c:280
____fput+0x16/0x20 fs/file_table.c:313
task_work_run+0x145/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4095e1
Code: Bad RIP value.
RSP: 002b:00007fff7e1c4910 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00000000004095e1
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006e7a1c R08: 00000000004b3370 R09: 00000000004b3370
R10: 00007fff7e1c4940 R11: 0000000000000293 R12: 00000000006e7a10
R13: 0000000000000001 R14: 000000000000002d R15: 20c49ba5e353f7cf
INFO: task syz-executor500:15000 blocked for more than 143 seconds.
Not tainted 5.5.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor500 D28536 15000 9197 0x00000004
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x934/0x1f90 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871
__down_common kernel/locking/semaphore.c:220 [inline]
__down+0x176/0x2c0 kernel/locking/semaphore.c:237
down+0x64/0x90 kernel/locking/semaphore.c:61
console_lock+0x29/0x80 kernel/printk/printk.c:2289
do_fb_ioctl+0x335/0x7d0 drivers/video/fbdev/core/fbmem.c:1101
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
vfs_ioctl fs/ioctl.c:47 [inline]
file_ioctl fs/ioctl.c:545 [inline]
do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
__do_sys_ioctl fs/ioctl.c:756 [inline]
__se_sys_ioctl fs/ioctl.c:754 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44aac9
Code: Bad RIP value.
RSP: 002b:00007f2e4eaddce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006e7a08 RCX: 000000000044aac9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 00000000006e7a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e7a0c
R13: 00007fff7e1c489f R14: 00007f2e4eade9c0 R15: 20c49ba5e353f7cf
INFO: task syz-executor500:15002 blocked for more than 143 seconds.
Not tainted 5.5.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor500 D27856 15002 9200 0x00000004
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x934/0x1f90 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871
__down_common kernel/locking/semaphore.c:220 [inline]
__down+0x176/0x2c0 kernel/locking/semaphore.c:237
down+0x64/0x90 kernel/locking/semaphore.c:61
console_lock+0x29/0x80 kernel/printk/printk.c:2289
do_fb_ioctl+0x335/0x7d0 drivers/video/fbdev/core/fbmem.c:1101
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
vfs_ioctl fs/ioctl.c:47 [inline]
file_ioctl fs/ioctl.c:545 [inline]
do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
__do_sys_ioctl fs/ioctl.c:756 [inline]
__se_sys_ioctl fs/ioctl.c:754 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44aac9
Code: Bad RIP value.
RSP: 002b:00007f2e4eaddce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006e7a08 RCX: 000000000044aac9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 00000000006e7a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e7a0c
R13: 00007fff7e1c489f R14: 00007f2e4eade9c0 R15: 20c49ba5e353f7cf
INFO: task syz-executor500:15003 blocked for more than 143 seconds.
Not tainted 5.5.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor500 D28536 15003 9201 0x00000004
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x934/0x1f90 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871
__down_common kernel/locking/semaphore.c:220 [inline]
__down+0x176/0x2c0 kernel/locking/semaphore.c:237
down+0x64/0x90 kernel/locking/semaphore.c:61
console_lock+0x29/0x80 kernel/printk/printk.c:2289
do_fb_ioctl+0x335/0x7d0 drivers/video/fbdev/core/fbmem.c:1101
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
vfs_ioctl fs/ioctl.c:47 [inline]
file_ioctl fs/ioctl.c:545 [inline]
do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
__do_sys_ioctl fs/ioctl.c:756 [inline]
__se_sys_ioctl fs/ioctl.c:754 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44aac9
Code: Bad RIP value.
RSP: 002b:00007f2e4eaddce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006e7a08 RCX: 000000000044aac9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 00000000006e7a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e7a0c
R13: 00007fff7e1c489f R14: 00007f2e4eade9c0 R15: 20c49ba5e353f7cf
INFO: task syz-executor500:15001 blocked for more than 143 seconds.
Not tainted 5.5.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor500 D28536 15001 9198 0x00000004
Call Trace:
context_switch kernel/sched/core.c:3385 [inline]
__schedule+0x934/0x1f90 kernel/sched/core.c:4081
schedule+0xdc/0x2b0 kernel/sched/core.c:4155
schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871
__down_common kernel/locking/semaphore.c:220 [inline]
__down+0x176/0x2c0 kernel/locking/semaphore.c:237
down+0x64/0x90 kernel/locking/semaphore.c:61
console_lock+0x29/0x80 kernel/printk/printk.c:2289
do_fb_ioctl+0x335/0x7d0 drivers/video/fbdev/core/fbmem.c:1101
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
vfs_ioctl fs/ioctl.c:47 [inline]
file_ioctl fs/ioctl.c:545 [inline]
do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
__do_sys_ioctl fs/ioctl.c:756 [inline]
__se_sys_ioctl fs/ioctl.c:754 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44aac9
Code: Bad RIP value.
RSP: 002b:00007f2e4eaddce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006e7a08 RCX: 000000000044aac9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 00000000006e7a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e7a0c
R13: 00007fff7e1c489f R14: 00007f2e4eade9c0 R15: 20c49ba5e353f7cf

Showing all locks held in the system:
1 lock held by khungtaskd/1114:
#0: ffffffff899a5680 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5334
1 lock held by rsyslogd/9076:
#0: ffff888094bf2420 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:801
2 locks held by getty/9166:
#0: ffff8880a06d2090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000169b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9167:
#0: ffff8880938e1090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900016cb2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9168:
#0: ffff8880a9a6f090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900016ab2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9169:
#0: ffff8880961a0090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900016d72e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9170:
#0: ffff88809d854090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000170b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9171:
#0: ffff8880a71ed090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000171b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by getty/9172:
#0: ffff88809841e090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900011102e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156
2 locks held by syz-executor500/14992:
1 lock held by syz-executor500/14993:
#0: ffff888218c7b070 (&fb_info->lock){+.+.}, at: lock_fb_info
include/linux/fb.h:637 [inline]
#0: ffff888218c7b070 (&fb_info->lock){+.+.}, at: fb_release+0x55/0x150
drivers/video/fbdev/core/fbmem.c:1435

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

NMI backtrace for cpu 1
CPU: 1 PID: 1114 Comm: khungtaskd Not tainted 5.5.0-rc2-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+0x197/0x210 lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x23b/0x28b 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:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline]
watchdog+0xb11/0x10c0 kernel/hung_task.c:289
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 14992 Comm: syz-executor500 Not tainted 5.5.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:cfb_fillrect+0x3f7/0x7c0
drivers/video/fbdev/core/cfbfillrect.c:325
Code: 48 b8 00 00 00 00 00 fc ff df 89 7d b8 48 c1 ea 03 44 89 7d c0 48 01
d0 48 89 45 b0 eb 03 4d 89 fe e8 0d 44 c0 fd 0f b6 4d b8 <89> d8 83 e3 3f
6a 00 44 8b 45 c0 41 b9 40 00 00 00 89 da 4c 89 e7
RSP: 0018:ffffc90005c3f330 EFLAGS: 00000293
RAX: ffff8880a8bbe400 RBX: 0000000000000000 RCX: 0000000000000006
RDX: 0000000000000000 RSI: ffffffff83b4e9e3 RDI: 0000000000000007
RBP: ffffc90005c3f398 R08: ffff8880a8bbe400 R09: 0000000000000040
R10: ffffed104319ae43 R11: ffff888218cd721f R12: ffff888218c7b000
R13: ffff8880000a0000 R14: 00000000b01f701f R15: 00000000b01f701f
FS: 00007f2e4eade700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006e00a0 CR3: 000000008cf8d000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
vga16fb_fillrect+0x6ce/0x19b0 drivers/video/fbdev/vga16fb.c:951
bit_clear_margins+0x30b/0x530 drivers/video/fbdev/core/bitblit.c:232
fbcon_clear_margins+0x1e9/0x250 drivers/video/fbdev/core/fbcon.c:1372
fbcon_switch+0xd7f/0x17f0 drivers/video/fbdev/core/fbcon.c:2354
redraw_screen+0x2b6/0x7d0 drivers/tty/vt/vt.c:997
fbcon_modechanged+0x5c3/0x790 drivers/video/fbdev/core/fbcon.c:2991
fbcon_update_vcs+0x42/0x50 drivers/video/fbdev/core/fbcon.c:3038
fb_set_var+0xb32/0xdd0 drivers/video/fbdev/core/fbmem.c:1051
do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104
fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180
vfs_ioctl fs/ioctl.c:47 [inline]
file_ioctl fs/ioctl.c:545 [inline]
do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
__do_sys_ioctl fs/ioctl.c:756 [inline]
__se_sys_ioctl fs/ioctl.c:754 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44aac9
Code: e8 7c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 1b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2e4eaddce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006e7a08 RCX: 000000000044aac9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 00000000006e7a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e7a0c
R13: 00007fff7e1c489f R14: 00007f2e4eade9c0 R15: 20c49ba5e353f7cf


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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