BUG: WARNING in dvb_frontend_get_event

[Yu Hao]

Hello,

We found the following issue using syzkaller on Linux v6.2.0.

In the function `dvb_frontend_get_event`, function
`wait_event_interruptible` is called
and the condition is `dvb_frontend_test_event(fepriv, events)`.
In the function `dvb_frontend_test_event`, function
`down(&fepriv->sem);` is called.
However, function `wait_event_interruptible` would put the process to sleep.
And function `down(&fepriv->sem);` may block the process.
So there is the issue with "do not call blocking ops when !TASK_RUNNING".

The full report including the Syzkaller reproducer & C reproducer:
https://gist.github.com/ZHYfeng/4c5f8be6adc63b73dba68230d15ece2c

The brief report is below:

Syzkaller hit 'WARNING in dvb_frontend_get_event' bug.

------------[ cut here ]------------
do not call blocking ops when !TASK_RUNNING; state=1 set at
[<ffffffff8161186d>] prepare_to_wait_event+0x6d/0x690
kernel/sched/wait.c:333
WARNING: CPU: 0 PID: 8017 at kernel/sched/core.c:9968
__might_sleep+0x10a/0x160 kernel/sched/core.c:9968
Modules linked in:
CPU: 0 PID: 8017 Comm: syz-executor303 Not tainted 6.2.0 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:__might_sleep+0x10a/0x160 kernel/sched/core.c:9968
Code: 9d 03 00 48 8d bb d8 16 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00
75 34 48 8b 93 d8 16 00 00 48 c7 c7 e0 68 4c 8a e8 38 55 72 08 <0f> 0b
e9 75 ff ff ff e8 1a 7b 7f 00 e9 26 ff ff ff 89 34 24 e8 1d
RSP: 0018:ffffc9000e537ac8 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff888018bdba80 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff888018bdba80 RDI: fffff52001ca6f4b
RBP: ffffffff8a4cd200 R08: 0000000000000000 R09: ffffed1005944f32
R10: ffff88802ca2798b R11: ffffed1005944f31 R12: 000000000000003a
R13: 0000000000000000 R14: 0000000000000000 R15: ffff888044057260
FS:  0000555555995880(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd34db66000 CR3: 000000001f479000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 down+0x1e/0xa0 kernel/locking/semaphore.c:58
 dvb_frontend_test_event drivers/media/dvb-core/dvb_frontend.c:277 [inline]
 dvb_frontend_get_event.isra.0+0x528/0x670
drivers/media/dvb-core/dvb_frontend.c:301
 dvb_frontend_handle_ioctl+0x1953/0x2ea0
drivers/media/dvb-core/dvb_frontend.c:2726
 dvb_frontend_do_ioctl+0x1c5/0x2f0 drivers/media/dvb-core/dvb_frontend.c:2097
 dvb_usercopy+0xbe/0x280 drivers/media/dvb-core/dvbdev.c:961
 dvb_frontend_ioctl+0x5a/0x80 drivers/media/dvb-core/dvb_frontend.c:2111
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x198/0x210 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f569e9f4a7d
Code: 28 c3 e8 36 29 00 00 66 0f 1f 44 00 00 f3 0f 1e fa 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff77694948 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f569e9f4a7d
RDX: 0000000020000000 RSI: 0000000080286f4e RDI: 0000000000000003
RBP: 00007f569e9ae440 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f569e9ae4e0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>