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Date
SubjectINFO: task hung in fb_open
From
Hello,

syzbot found the following crash on:

HEAD commit: 596cf45c Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1599f641e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7d8ab2e0e09c2a82
dashboard link: https://syzkaller.appspot.com/bug?extid=a4ae1442ccc637162dc1
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14273edae00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15e7677ae00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a4ae1442ccc637162dc1@syzkaller.appspotmail.com

INFO: task syz-executor823:8749 blocked for more than 143 seconds.
Not tainted 5.4.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor823 D28160 8749 8748 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_preempt_disabled+0x13/0x20 kernel/sched/core.c:4214
__mutex_lock_common kernel/locking/mutex.c:1036 [inline]
__mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
lock_fb_info include/linux/fb.h:637 [inline]
fb_open+0xd7/0x450 drivers/video/fbdev/core/fbmem.c:1406
chrdev_open+0x245/0x6b0 fs/char_dev.c:414
do_dentry_open+0x4e6/0x1380 fs/open.c:797
vfs_open+0xa0/0xd0 fs/open.c:914
do_last fs/namei.c:3412 [inline]
path_openat+0x10e4/0x4710 fs/namei.c:3529
do_filp_open+0x1a1/0x280 fs/namei.c:3559
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
__do_sys_openat fs/open.c:1124 [inline]
__se_sys_openat fs/open.c:1118 [inline]
__x64_sys_openat+0x9d/0x100 fs/open.c:1118
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441419
Code: Bad RIP value.
RSP: 002b:00007fffaaef6f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441419
RDX: 0000000000000000 RSI: 0000000020000840 RDI: ffffffffffffff9c
RBP: 00000000006cb018 R08: 0000000000000004 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402190
R13: 0000000000402220 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor823:8750 blocked for more than 143 seconds.
Not tainted 5.4.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor823 D28160 8750 8747 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_preempt_disabled+0x13/0x20 kernel/sched/core.c:4214
__mutex_lock_common kernel/locking/mutex.c:1036 [inline]
__mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
lock_fb_info include/linux/fb.h:637 [inline]
fb_open+0xd7/0x450 drivers/video/fbdev/core/fbmem.c:1406
chrdev_open+0x245/0x6b0 fs/char_dev.c:414
do_dentry_open+0x4e6/0x1380 fs/open.c:797
vfs_open+0xa0/0xd0 fs/open.c:914
do_last fs/namei.c:3412 [inline]
path_openat+0x10e4/0x4710 fs/namei.c:3529
do_filp_open+0x1a1/0x280 fs/namei.c:3559
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
__do_sys_openat fs/open.c:1124 [inline]
__se_sys_openat fs/open.c:1118 [inline]
__x64_sys_openat+0x9d/0x100 fs/open.c:1118
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441419
Code: Bad RIP value.
RSP: 002b:00007fffaaef6f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441419
RDX: 0000000000000000 RSI: 0000000020000840 RDI: ffffffffffffff9c
RBP: 00000000006cb018 R08: 0000000000000004 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402190
R13: 0000000000402220 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor823:8751 blocked for more than 143 seconds.
Not tainted 5.4.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor823 D28160 8751 8745 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:1036 [inline]
__mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
lock_fb_info include/linux/fb.h:637 [inline]
fb_open+0xd7/0x450 drivers/video/fbdev/core/fbmem.c:1406
chrdev_open+0x245/0x6b0 fs/char_dev.c:414
do_dentry_open+0x4e6/0x1380 fs/open.c:797
vfs_open+0xa0/0xd0 fs/open.c:914
do_last fs/namei.c:3412 [inline]
path_openat+0x10e4/0x4710 fs/namei.c:3529
do_filp_open+0x1a1/0x280 fs/namei.c:3559
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
__do_sys_openat fs/open.c:1124 [inline]
__se_sys_openat fs/open.c:1118 [inline]
__x64_sys_openat+0x9d/0x100 fs/open.c:1118
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441419
Code: Bad RIP value.
RSP: 002b:00007fffaaef6f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441419
RDX: 0000000000000000 RSI: 0000000020000840 RDI: ffffffffffffff9c
RBP: 00000000006cb018 R08: 0000000000000004 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402190
R13: 0000000000402220 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor823:8752 blocked for more than 143 seconds.
Not tainted 5.4.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor823 D27992 8752 8743 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:1036 [inline]
__mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
lock_fb_info include/linux/fb.h:637 [inline]
fb_open+0xd7/0x450 drivers/video/fbdev/core/fbmem.c:1406
chrdev_open+0x245/0x6b0 fs/char_dev.c:414
do_dentry_open+0x4e6/0x1380 fs/open.c:797
vfs_open+0xa0/0xd0 fs/open.c:914
do_last fs/namei.c:3412 [inline]
path_openat+0x10e4/0x4710 fs/namei.c:3529
do_filp_open+0x1a1/0x280 fs/namei.c:3559
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
__do_sys_openat fs/open.c:1124 [inline]
__se_sys_openat fs/open.c:1118 [inline]
__x64_sys_openat+0x9d/0x100 fs/open.c:1118
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441419
Code: Bad RIP value.
RSP: 002b:00007fffaaef6f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441419
RDX: 0000000000000000 RSI: 0000000020000840 RDI: ffffffffffffff9c
RBP: 00000000006cb018 R08: 0000000000000004 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402190
R13: 0000000000402220 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor823:8753 blocked for more than 143 seconds.
Not tainted 5.4.0-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor823 D28160 8753 8746 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_preempt_disabled+0x13/0x20 kernel/sched/core.c:4214
__mutex_lock_common kernel/locking/mutex.c:1036 [inline]
__mutex_lock+0x7ab/0x13c0 kernel/locking/mutex.c:1106
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121
lock_fb_info include/linux/fb.h:637 [inline]
fb_open+0xd7/0x450 drivers/video/fbdev/core/fbmem.c:1406
chrdev_open+0x245/0x6b0 fs/char_dev.c:414
do_dentry_open+0x4e6/0x1380 fs/open.c:797
vfs_open+0xa0/0xd0 fs/open.c:914
do_last fs/namei.c:3412 [inline]
path_openat+0x10e4/0x4710 fs/namei.c:3529
do_filp_open+0x1a1/0x280 fs/namei.c:3559
do_sys_open+0x3fe/0x5d0 fs/open.c:1097
__do_sys_openat fs/open.c:1124 [inline]
__se_sys_openat fs/open.c:1118 [inline]
__x64_sys_openat+0x9d/0x100 fs/open.c:1118
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441419
Code: Bad RIP value.
RSP: 002b:00007fffaaef6f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441419
RDX: 0000000000000000 RSI: 0000000020000840 RDI: ffffffffffffff9c
RBP: 00000000006cb018 R08: 0000000000000004 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402190
R13: 0000000000402220 R14: 0000000000000000 R15: 0000000000000000

Showing all locks held in the system:
1 lock held by khungtaskd/1105:
#0: ffffffff897a4240 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5334
1 lock held by rsyslogd/8626:
#0: ffff888099d3e860 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:801
2 locks held by getty/8716:
#0: ffff888090469090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000178b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by getty/8717:
#0: ffff888096224090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900017eb2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by getty/8718:
#0: ffff888095f16090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000174b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by getty/8719:
#0: ffff8880a7b99090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900017bb2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by getty/8720:
#0: ffff8880a8021090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000177b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by getty/8721:
#0: ffff8880a8ac3090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc900017db2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by getty/8722:
#0: ffff8880a7a59090 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
#1: ffffc9000172b2e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1c10 drivers/tty/n_tty.c:2156
2 locks held by syz-executor823/8744:
1 lock held by syz-executor823/8749:
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: lock_fb_info
include/linux/fb.h:637 [inline]
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: fb_open+0xd7/0x450
drivers/video/fbdev/core/fbmem.c:1406
1 lock held by syz-executor823/8750:
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: lock_fb_info
include/linux/fb.h:637 [inline]
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: fb_open+0xd7/0x450
drivers/video/fbdev/core/fbmem.c:1406
1 lock held by syz-executor823/8751:
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: lock_fb_info
include/linux/fb.h:637 [inline]
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: fb_open+0xd7/0x450
drivers/video/fbdev/core/fbmem.c:1406
1 lock held by syz-executor823/8752:
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: lock_fb_info
include/linux/fb.h:637 [inline]
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: fb_open+0xd7/0x450
drivers/video/fbdev/core/fbmem.c:1406
1 lock held by syz-executor823/8753:
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: lock_fb_info
include/linux/fb.h:637 [inline]
#0: ffff8880a3d59070 (&fb_info->lock){+.+.}, at: fb_open+0xd7/0x450
drivers/video/fbdev/core/fbmem.c:1406

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

NMI backtrace for cpu 1
CPU: 1 PID: 1105 Comm: khungtaskd Not tainted 5.4.0-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: 8744 Comm: syz-executor823 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:199 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:70 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x20/0x50 kernel/kcov.c:102
Code: ff cc cc cc cc cc cc cc cc cc 55 48 89 e5 65 48 8b 04 25 c0 1e 02 00
65 8b 15 f4 23 8d 7e 81 e2 00 01 1f 00 48 8b 75 08 75 2b <8b> 90 80 13 00
00 83 fa 02 75 20 48 8b 88 88 13 00 00 8b 80 84 13
RSP: 0018:ffffc90001e072c8 EFLAGS: 00000246
RAX: ffff8880a5382000 RBX: 0000000000000000 RCX: ffffffff83b3479d
RDX: 0000000000000000 RSI: ffffffff83b34766 RDI: 0000000000000005
RBP: ffffc90001e072c8 R08: ffff8880a5382000 R09: 0000000000000040
R10: ffffed10147a952b R11: ffff8880a3d4a95f R12: 0000000000000050
R13: 0000000000000048 R14: ffff8880000a0000 R15: ffff8880000a0040
FS: 0000000000cbb880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 0000000098fe3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
bitfill_aligned drivers/video/fbdev/core/cfbfillrect.c:64 [inline]
bitfill_aligned+0x106/0x210 drivers/video/fbdev/core/cfbfillrect.c:35
cfb_fillrect+0x423/0x7c0 drivers/video/fbdev/core/cfbfillrect.c:327
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:539 [inline]
do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:726
ksys_ioctl+0xab/0xd0 fs/ioctl.c:743
__do_sys_ioctl fs/ioctl.c:750 [inline]
__se_sys_ioctl fs/ioctl.c:748 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:748
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441419
Code: e8 ac e8 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 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffaaef6f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441419
RDX: 0000000020000180 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 00000000006cb018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000402190
R13: 0000000000402220 R14: 0000000000000000 R15: 0000000000000000


---
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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