INFO: task hung in do_fb_ioctl (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 399849e4 Linux 4.19.131
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=160e0fe5100000
kernel config: https://syzkaller.appspot.com/x/.config?x=eada6d424d8bae1d
dashboard link: https://syzkaller.appspot.com/bug?extid=0d580edd5df3dc9178e5
compiler: gcc (GCC) 10.1.0-syz 20200507

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+0d580e...@syzkaller.appspotmail.com

NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
NOHZ: local_softirq_pending 08
INFO: task syz-executor.2:11802 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D28784 11802 6684 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
lock_fb_info drivers/video/fbdev/core/fbmem.c:81 [inline]
do_fb_ioctl+0x449/0xb50 drivers/video/fbdev/core/fbmem.c:1123
fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1230
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: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007f40e3189c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e5460 RCX: 000000000045cb29
RDX: 0000000020000180 RSI: 0000000000004602 RDI: 0000000000000005
RBP: 000000000078c040 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002f8 R14: 00000000004c5831 R15: 00007f40e318a6d4
INFO: task syz-executor.1:11807 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D29520 11807 6550 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007f6fbe7ebc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007f6fbe7ec6d4
INFO: task syz-executor.4:11812 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4 D29520 11812 6749 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007ff9122c8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007ff9122c96d4
INFO: task syz-executor.4:11818 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4 D28096 11818 6749 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007ff9122a7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007ff9122a86d4
INFO: task syz-executor.3:11811 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3 D28184 11811 6730 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007f1817395c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007f18173966d4
INFO: task syz-executor.5:11814 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D29520 11814 6988 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007fb723a51c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000000000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007fb723a526d4
INFO: task syz-executor.0:11813 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0 D29520 11813 6431 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007f687068bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000004000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007f687068c6d4
INFO: task syz-executor.0:11817 blocked for more than 140 seconds.
Not tainted 4.19.131-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0 D28712 11817 6431 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3515
schedule+0x8d/0x1b0 kernel/sched/core.c:3559
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3617
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x647/0x1260 kernel/locking/mutex.c:1072
fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
chrdev_open+0x266/0x770 fs/char_dev.c:423
do_dentry_open+0x4aa/0x1160 fs/open.c:796
do_last fs/namei.c:3421 [inline]
path_openat+0x793/0x2df0 fs/namei.c:3537
do_filp_open+0x18c/0x3f0 fs/namei.c:3567
do_sys_open+0x3b3/0x520 fs/open.c:1085
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45cb29
Code: 48 8b 6c 24 20 48 83 c4 28 c3 48 8b 80 c8 00 00 00 48 39 c8 74 e5 48 8b 44 24 30 48 89 04 24 48 8b 44 24 38 48 89 44 24 08 0f <b6> 44 24 48 88 44 24 10 0f b6 44 24 49 88 44 24 11 0f b6 44 24 4a
RSP: 002b:00007f687066ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000004f86a0 RCX: 000000000045cb29
RDX: 0000000004000000 RSI: 0000000020000180 RDI: ffffffffffffff9c
RBP: 000000000078bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000007c1 R14: 00000000004caafb R15: 00007f687066b6d4

Showing all locks held in the system:
1 lock held by khungtaskd/1073:
#0: 000000002038c0c1 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
1 lock held by in:imklog/6124:
#0: 000000009c5796ff (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767
3 locks held by syz-executor.2/11784:
1 lock held by syz-executor.2/11802:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: lock_fb_info drivers/video/fbdev/core/fbmem.c:81 [inline]
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: do_fb_ioctl+0x449/0xb50 drivers/video/fbdev/core/fbmem.c:1123
1 lock held by syz-executor.1/11807:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
1 lock held by syz-executor.4/11812:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
1 lock held by syz-executor.4/11818:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
1 lock held by syz-executor.3/11811:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
1 lock held by syz-executor.5/11814:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
1 lock held by syz-executor.0/11813:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457
1 lock held by syz-executor.0/11817:
#0: 0000000060e9d0ea (&fb_info->lock){+.+.}, at: fb_open+0xd3/0x430 drivers/video/fbdev/core/fbmem.c:1457

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

NMI backtrace for cpu 1
CPU: 1 PID: 1073 Comm: khungtaskd Not tainted 4.19.131-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+0x1fc/0x2fe lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x991/0xe60 kernel/hung_task.c:287
kthread+0x30b/0x410 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 11784 Comm: syz-executor.2 Not tainted 4.19.131-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__sanitizer_cov_trace_pc+0x22/0x50 kernel/kcov.c:101
Code: 00 00 e9 39 ec ff ff 90 48 8b 34 24 65 48 8b 04 25 40 ee 01 00 65 8b 15 7c 45 98 7e 81 e2 00 01 1f 00 75 2b 8b 90 d8 12 00 00 <83> fa 02 75 20 48 8b 88 e0 12 00 00 8b 80 dc 12 00 00 48 8b 11 48
RSP: 0018:ffff888042ca72b8 EFLAGS: 00000246
RAX: ffff888096ebc340 RBX: 0000000000000050 RCX: ffffffff8385d3d4
RDX: 0000000000000002 RSI: ffffffff8385d3c0 RDI: 0000000000000004
RBP: 000000000000001a R08: 0000000000000001 R09: 0000000000000050
R10: 0000000000000004 R11: 0000000000000000 R12: ffff8880000a001a
R13: ffff8880000a0000 R14: 0000000000000000 R15: 00000000f05f674f
FS: 00007f40e31cc700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 0000000089886000 CR4: 00000000001406f0
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+0x9c0/0x1940 drivers/video/fbdev/vga16fb.c:923
bit_clear_margins+0x2d5/0x4a0 drivers/video/fbdev/core/bitblit.c:232
fbcon_clear_margins+0x1e2/0x350 drivers/video/fbdev/core/fbcon.c:1342
fbcon_switch+0x1038/0x1d26 drivers/video/fbdev/core/fbcon.c:2324
redraw_screen+0x37d/0x870 drivers/tty/vt/vt.c:1015
fbcon_modechanged+0x6e9/0x9f0 drivers/video/fbdev/core/fbcon.c:2972
fbcon_event_notify+0x197/0x1d80 drivers/video/fbdev/core/fbcon.c:3347
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_set_var+0xc51/0xe20 drivers/video/fbdev/core/fbmem.c:1042
do_fb_ioctl+0x3cf/0xb50 drivers/video/fbdev/core/fbmem.c:1115
fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1230
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: 0033:0x45cb29
Code: 0d b7 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 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f40e31cbc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e55a0 RCX: 000000000045cb29
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000005
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000002fd R14: 00000000004c58a5 R15: 00007f40e31cc6d4


---
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 syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 2c746135 Linux 4.19.158
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14936805500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c19abec6250dfe36

dashboard link: https://syzkaller.appspot.com/bug?extid=0d580edd5df3dc9178e5
compiler: gcc (GCC) 10.1.0-syz 20200507

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=146d311e500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15295139500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0d580e...@syzkaller.appspotmail.com

INFO: task syz-executor443:8525 blocked for more than 140 seconds.
Not tainted 4.19.158-syzkaller #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

syz-executor443 D28648 8525 8094 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
schedule_timeout+0x92d/0xfe0 kernel/time/timer.c:1794
__down_common kernel/locking/semaphore.c:221 [inline]
__down+0x183/0x2a0 kernel/locking/semaphore.c:238
down+0x57/0x80 kernel/locking/semaphore.c:62
console_lock+0x25/0x80 kernel/printk/printk.c:2275
do_fb_ioctl+0x33e/0xb50 drivers/video/fbdev/core/fbmem.c:1109

fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1230
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: 0033:0x445189
Code: Bad RIP value.
RSP: 002b:00007ffe06dac238 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000020000080 RCX: 0000000000445189
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 0000000000087630 R08: 00000000004002e0 R09: 00000000004002e0
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000402350
R13: 00000000004023e0 R14: 0000000000000000 R15: 0000000000000000

Showing all locks held in the system:

7 locks held by kworker/u4:2/101:
1 lock held by khungtaskd/1567:
#0: 00000000c59e5605 (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440
1 lock held by in:imklog/7789:
#0: 00000000e998af56 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x26f/0x310 fs/file.c:767
2 locks held by agetty/7802:
#0: 0000000086fa765f (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
#1: 0000000035130b29 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x217/0x1950 drivers/tty/n_tty.c:2154

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

NMI backtrace for cpu 0
CPU: 0 PID: 1567 Comm: khungtaskd Not tainted 4.19.158-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+0x1fc/0x2fe lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x991/0xe60 kernel/hung_task.c:287

kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:

NMI backtrace for cpu 1

CPU: 1 PID: 101 Comm: kworker/u4:2 Not tainted 4.19.158-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Workqueue: events_unbound flush_to_ldisc
RIP: 0010:vga16fb_fillrect+0x9d4/0x1940 drivers/video/fbdev/vga16fb.c:922
Code: ff 89 de 31 ed e8 4c 6e bc fd 85 db 4d 89 ec 74 22 e8 d0 6c bc fd 45 88 34 24 83 c5 01 89 df 49 83 c4 01 89 ee e8 ac 6d bc fd <39> eb 75 e3 89 d8 49 01 c5 e8 ae 6c bc fd 31 ff 44 89 fe 4c 03 2c
RSP: 0018:ffff8880b53c74d0 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000050 RCX: ffffffff83a86344
RDX: 000000000000003c RSI: ffff8880b53bc3c0 RDI: 0000000000000004
RBP: 000000000000003c R08: 0000000000000010 R09: 0000000000000050
R10: 0000000000000004 R11: 0000000000000000 R12: ffff8880000a003c
R13: ffff8880000a0000 R14: 0000000000000000 R15: 00000000e8bc1d07
FS: 0000000000000000(0000) GS:ffff8880ba100000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00000000006d0080 CR3: 00000000a46c2000 CR4: 00000000001406e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:

bit_clear+0x382/0x4d0 drivers/video/fbdev/core/bitblit.c:74
fbcon_clear+0x5d6/0x690 drivers/video/fbdev/core/fbcon.c:1258
fbcon_scroll+0x42e/0x3440 drivers/video/fbdev/core/fbcon.c:1756
con_scroll+0x5f8/0x720 drivers/tty/vt/vt.c:637
lf+0x262/0x2b0 drivers/tty/vt/vt.c:1491
do_con_write+0x133e/0x1d90 drivers/tty/vt/vt.c:2768
con_put_char+0x96/0xe0 drivers/tty/vt/vt.c:3155
tty_put_char+0xb7/0x150 drivers/tty/tty_io.c:2887
do_output_char+0x155/0x850 drivers/tty/n_tty.c:486
__process_echoes+0x38e/0x9f0 drivers/tty/n_tty.c:737
flush_echoes drivers/tty/n_tty.c:827 [inline]
__receive_buf drivers/tty/n_tty.c:1646 [inline]
n_tty_receive_buf_common+0xc0c/0x2a90 drivers/tty/n_tty.c:1740
tty_ldisc_receive_buf+0xa9/0x190 drivers/tty/tty_buffer.c:456
tty_port_default_receive_buf+0x78/0xa0 drivers/tty/tty_port.c:38
receive_buf drivers/tty/tty_buffer.c:476 [inline]
flush_to_ldisc+0x21f/0x390 drivers/tty/tty_buffer.c:528
process_one_work+0x864/0x1570 kernel/workqueue.c:2155
worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 6be10fb6c143608a7c7ab3901a096e272233bf64
Author: George Kennedy <george....@oracle.com>
Date: Tue Jul 7 19:26:03 2020 +0000

fbmem: add margin check to fb_check_caps()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14dd639b300000
start commit: 13d2ce42de8c Linux 4.19.163
git tree: linux-4.19.y
kernel config: https://syzkaller.appspot.com/x/.config?x=fac7c3360835a4e0
dashboard link: https://syzkaller.appspot.com/bug?extid=0d580edd5df3dc9178e5
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=107c0613500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1735c937500000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: fbmem: add margin check to fb_check_caps()

For information about bisection process see: https://goo.gl/tpsmEJ#bisection