Re: [PATCH] posix-timers: fix oops in clock_nanosleep() with CLOCK_MONOTONIC_RAW

[Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>]

Andrew Morton wrote:
> On Mon, 03 Aug 2009 11:48:19 +0900 Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> wrote:
> 
>> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>>
>> Prevent calling do_nanosleep() with clockid CLOCK_MONOTONIC_RAW, it may
>> cause oops, such as NULL pointer dereference.
>>
>> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>> ---
>>  kernel/posix-timers.c |    7 +++++++
>>  1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
>> index 052ec4d..d089d05 100644
>> --- a/kernel/posix-timers.c
>> +++ b/kernel/posix-timers.c
>> @@ -202,6 +202,12 @@ static int no_timer_create(struct k_itimer *new_timer)
>>  	return -EOPNOTSUPP;
>>  }
>>  
>> +static int no_nsleep(const clockid_t which_clock, int flags,
>> +		     struct timespec *tsave, struct timespec __user *rmtp)
>> +{
>> +	return -EOPNOTSUPP;
>> +}
>> +
>>  /*
>>   * Return nonzero if we know a priori this clockid_t value is bogus.
>>   */
>> @@ -254,6 +260,7 @@ static __init int init_posix_timers(void)
>>  		.clock_get = posix_get_monotonic_raw,
>>  		.clock_set = do_posix_clock_nosettime,
>>  		.timer_create = no_timer_create,
>> +		.nsleep = no_nsleep,
>>  	};
>>  
>>  	register_posix_clock(CLOCK_REALTIME, &clock_realtime);
> 
> Under which circumstances will this oops trigger?
> 
> What userspace setup/actions will trigger the oops?

Sorry for the lack of information.
Userspace program is like this;

#include <time.h>

int main(void)
{
	struct timespec ts;

	ts.tv_sec = 1;
	ts.tv_nsec = 0;

	return clock_nanosleep(4, 0, &ts, NULL);
}

and it will cause oops;

BUG: unable to handle kernel NULL pointer dereference at 0000000000000001
IP: [<ffffffff81029eb5>] __ticket_spin_lock+0x9/0x1a
PGD 3dc6c067 PUD 3b519067 PMD 0 
Oops: 0002 [#1] SMP 
last sysfs file: /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/irq
CPU 0 
Modules linked in: sco bnep l2cap bluetooth sunrpc bridge stp llc ipv6 p4_clockmod speedstep_lib freq_table dm_multipath uinput iTCO_wdt iTCO_vendor_support tg3 i2c_i801 snd_intel8x0 snd_ac97_codec ac97_bus ppdev snd_pcm parport_pc snd_timer floppy parport snd soundcore snd_page_alloc pcspkr ata_generic pata_acpi nouveau drm i2c_algo_bit i2c_core [last unloaded: freq_table]
Pid: 20114, comm: a.out Not tainted 2.6.29.6-213.fc11.x86_64 #1 PC-MY32EXZE78SG
RIP: 0010:[<ffffffff81029eb5>]  [<ffffffff81029eb5>] __ticket_spin_lock+0x9/0x1a
RSP: 0018:ffff88003e08bd88  EFLAGS: 00010046
RAX: 0000000000000100 RBX: 0000000000000001 RCX: 0000000000000001
RDX: 000000000000c350 RSI: 0000000000000286 RDI: 0000000000000001
RBP: ffff88003e08bd88 R08: 0000000000000001 R09: 0000003ec680eec0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000286
R13: ffff88003e08be20 R14: 000000000000c350 R15: 000000000000c350
FS:  00007fb6cd3996f0(0000) GS:ffffffff817b7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000001 CR3: 000000003a5c0000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process a.out (pid: 20114, threadinfo ffff88003e08a000, task ffff8800399e1700)
Stack:
 ffff88003e08bd98 ffffffff81029f7f ffff88003e08bdb8 ffffffff813ac07c
 ffff880001011178 ffff88003e08be98 ffff88003e08bde8 ffffffff8105f3a1
 ffff88003e08bdd8 ffff88003e08be98 0000000000000001 000000003b9aca00
Call Trace:
 [<ffffffff81029f7f>] default_spin_lock_flags+0x9/0xe
 [<ffffffff813ac07c>] _spin_lock_irqsave+0x32/0x3b
 [<ffffffff8105f3a1>] lock_hrtimer_base+0x2a/0x50
 [<ffffffff8105f527>] __hrtimer_start_range_ns+0x2f/0x238
 [<ffffffff8105f75e>] hrtimer_start_range_ns+0x14/0x16
 [<ffffffff813aac8b>] do_nanosleep+0x4e/0xae
 [<ffffffff8105f813>] hrtimer_nanosleep+0xb3/0x123
 [<ffffffff8105edea>] ? hrtimer_wakeup+0x0/0x26
 [<ffffffff8105b4ed>] sys_clock_nanosleep+0xc9/0xdf
 [<ffffffff8101133a>] system_call_fastpath+0x16/0x1b
Code: 9c 02 81 44 89 c6 48 89 c7 e8 0a fb ff ff eb 0f 0f b7 f6 40 0f b6 ff 48 89 c2 e8 1c fb ff ff c9 c3 90 55 b8 00 01 00 00 48 89 e5 <f0> 66 0f c1 07 38 e0 74 06 f3 90 8a 07 eb f6 c9 c3 55 48 89 e5 
RIP  [<ffffffff81029eb5>] __ticket_spin_lock+0x9/0x1a
 RSP <ffff88003e08bd88>
CR2: 0000000000000001
---[ end trace e83b583836779b24 ]---

thanks,
Hiroshi