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From: Jens Axboe <axboe@kernel.dk>
To: Tony Battersby <tonyb@cybernetics.com>,
	Olivier Langlois <olivier@trillion01.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	io-uring <io-uring@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Pavel Begunkov>" <asml.silence@gmail.com>
Subject: Re: [PATCH] coredump: Limit what can interrupt coredumps
Date: Wed, 18 Aug 2021 08:46:30 -0600	[thread overview]
Message-ID: <90c35bf6-bf65-c997-1823-36c509cf72b1@kernel.dk> (raw)
In-Reply-To: <16ded7e5-1f44-1c51-5759-35f835115665@cybernetics.com>

On 8/18/21 8:37 AM, Tony Battersby wrote:
> On 8/17/21 6:05 PM, Jens Axboe wrote:
>> On 8/17/21 3:39 PM, Tony Battersby wrote:
>>> On 8/17/21 5:28 PM, Jens Axboe wrote:
>>>> Another approach - don't allow TWA_SIGNAL task_work to get queued if
>>>> PF_SIGNALED has been set on the task. This is similar to how we reject
>>>> task_work_add() on process exit, and the callers must be able to handle
>>>> that already.
>>>>
>>>> Can you test this one on top of your 5.10-stable?
>>>>
>>>>
>>>> diff --git a/fs/coredump.c b/fs/coredump.c
>>>> index 07afb5ddb1c4..ca7c1ee44ada 100644
>>>> --- a/fs/coredump.c
>>>> +++ b/fs/coredump.c
>>>> @@ -602,6 +602,14 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>>>>  		.mm_flags = mm->flags,
>>>>  	};
>>>>  
>>>> +	/*
>>>> +	 * task_work_add() will refuse to add work after PF_SIGNALED has
>>>> +	 * been set, ensure that we flush any pending TIF_NOTIFY_SIGNAL work
>>>> +	 * if any was queued before that.
>>>> +	 */
>>>> +	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
>>>> +		tracehook_notify_signal();
>>>> +
>>>>  	audit_core_dumps(siginfo->si_signo);
>>>>  
>>>>  	binfmt = mm->binfmt;
>>>> diff --git a/kernel/task_work.c b/kernel/task_work.c
>>>> index 1698fbe6f0e1..1ab28904adc4 100644
>>>> --- a/kernel/task_work.c
>>>> +++ b/kernel/task_work.c
>>>> @@ -41,6 +41,12 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
>>>>  		head = READ_ONCE(task->task_works);
>>>>  		if (unlikely(head == &work_exited))
>>>>  			return -ESRCH;
>>>> +		/*
>>>> +		 * TIF_NOTIFY_SIGNAL notifications will interfere with
>>>> +		 * a core dump in progress, reject them.
>>>> +		 */
>>>> +		if ((task->flags & PF_SIGNALED) && notify == TWA_SIGNAL)
>>>> +			return -ESRCH;
>>>>  		work->next = head;
>>>>  	} while (cmpxchg(&task->task_works, head, work) != head);
>>>>  
>>>>
>>> Doesn't compile.  5.10 doesn't have TIF_NOTIFY_SIGNAL.
>> Oh right... Here's one hacked up for the 5.10 TWA_SIGNAL setup. Totally
>> untested...
>>
>> diff --git a/fs/coredump.c b/fs/coredump.c
>> index c6acfc694f65..9e899ce67589 100644
>> --- a/fs/coredump.c
>> +++ b/fs/coredump.c
>> @@ -603,6 +603,19 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>>  		.mm_flags = mm->flags,
>>  	};
>>  
>> +	/*
>> +	 * task_work_add() will refuse to add work after PF_SIGNALED has
>> +	 * been set, ensure that we flush any pending TWA_SIGNAL work
>> +	 * if any was queued before that.
>> +	 */
>> +	if (signal_pending(current) && (current->jobctl & JOBCTL_TASK_WORK)) {
>> +		task_work_run();
>> +		spin_lock_irq(&current->sighand->siglock);
>> +		current->jobctl &= ~JOBCTL_TASK_WORK;
>> +		recalc_sigpending();
>> +		spin_unlock_irq(&current->sighand->siglock);
>> +	}
>> +
>>  	audit_core_dumps(siginfo->si_signo);
>>  
>>  	binfmt = mm->binfmt;
>> diff --git a/kernel/task_work.c b/kernel/task_work.c
>> index 8d6e1217c451..93b3f262eb4a 100644
>> --- a/kernel/task_work.c
>> +++ b/kernel/task_work.c
>> @@ -39,6 +39,12 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
>>  		head = READ_ONCE(task->task_works);
>>  		if (unlikely(head == &work_exited))
>>  			return -ESRCH;
>> +		/*
>> +		 * TWA_SIGNAL notifications will interfere with
>> +		 * a core dump in progress, reject them.
>> +		 */
>> +		if ((task->flags & PF_SIGNALED) && notify == TWA_SIGNAL)
>> +			return -ESRCH;
>>  		work->next = head;
>>  	} while (cmpxchg(&task->task_works, head, work) != head);
>>  
>>
> Tested with 5.10.59 + backport 06af8679449d + the patch above.  That
> fixes it for me.  I tested a couple of variations to make sure.
> 
> Thanks!
> 
> Tested-by: Tony Battersby <tonyb@cybernetics.com>

Great, thanks for testing! The 5.10 version is a bit uglier due to how
TWA_SIGNAL used to work, but it's the most straight forward backport of
the other version I sent.

-- 
Jens Axboe


  reply	other threads:[~2021-08-18 14:46 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com>
     [not found] ` <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com>
     [not found]   ` <87h7i694ij.fsf_-_@disp2133>
2021-06-09 20:33     ` [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL Linus Torvalds
2021-06-09 20:48       ` Eric W. Biederman
2021-06-09 20:52         ` Linus Torvalds
2021-06-09 21:02       ` Olivier Langlois
2021-06-09 21:05         ` Eric W. Biederman
2021-06-09 21:26           ` Olivier Langlois
2021-06-09 21:56             ` Olivier Langlois
2021-06-10 14:26             ` Eric W. Biederman
2021-06-10 15:17               ` Olivier Langlois
2021-06-10 18:58               ` [CFT}[PATCH] coredump: Limit what can interrupt coredumps Eric W. Biederman
2021-06-10 19:10                 ` Linus Torvalds
2021-06-10 19:18                   ` Eric W. Biederman
2021-06-10 19:50                     ` Linus Torvalds
2021-06-10 20:11                       ` [PATCH] " Eric W. Biederman
2021-06-10 21:04                         ` Linus Torvalds
2021-06-12 14:36                         ` Olivier Langlois
2021-06-12 16:26                           ` Jens Axboe
2021-06-14 14:10                         ` Oleg Nesterov
2021-06-14 16:37                           ` Eric W. Biederman
2021-06-14 16:59                             ` Oleg Nesterov
2021-06-15 22:08                           ` Eric W. Biederman
2021-06-16 19:23                             ` Olivier Langlois
2021-06-16 20:00                               ` Eric W. Biederman
2021-06-18 20:05                                 ` Olivier Langlois
2021-08-05 13:06                             ` Olivier Langlois
2021-08-10 21:48                               ` Tony Battersby
2021-08-11 20:47                                 ` Olivier Langlois
2021-08-12  1:55                                 ` Jens Axboe
2021-08-12 13:53                                   ` Tony Battersby
2021-08-15 20:42                                   ` Olivier Langlois
2021-08-16 13:02                                     ` Pavel Begunkov
2021-08-16 13:06                                       ` Pavel Begunkov
2021-08-17 18:15                                     ` Jens Axboe
2021-08-17 18:24                                       ` Jens Axboe
2021-08-17 19:29                                         ` Tony Battersby
2021-08-17 19:59                                           ` Jens Axboe
2021-08-17 21:28                                             ` Jens Axboe
2021-08-17 21:39                                               ` Tony Battersby
2021-08-17 22:05                                                 ` Jens Axboe
2021-08-18 14:37                                                   ` Tony Battersby
2021-08-18 14:46                                                     ` Jens Axboe [this message]
2021-08-18  2:57                                               ` Jens Axboe
2021-08-18  2:58                                                 ` Jens Axboe
2021-08-21 10:08                                                 ` Olivier Langlois
2021-08-21 16:47                                                   ` Olivier Langlois
2021-08-21 16:51                                                     ` Jens Axboe
2021-08-21 17:21                                                       ` Olivier Langlois
2021-08-21  9:52                                         ` Olivier Langlois
2021-08-21  9:48                                       ` Olivier Langlois
2021-10-22 14:13     ` [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL Pavel Begunkov
2021-12-24  1:34       ` Olivier Langlois
2021-12-24 10:37         ` Pavel Begunkov
2021-12-24 19:52           ` Eric W. Biederman
2021-12-28 11:24             ` Pavel Begunkov
2022-03-14 23:58               ` Eric W. Biederman
     [not found]                 ` <8218f1a245d054c940e25142fd00a5f17238d078.camel@trillion01.com>
2022-06-01  3:15                   ` Jens Axboe
2022-07-20 16:49                     ` [PATCH 0/2] coredump: Allow io_uring using apps to dump to pipes Eric W. Biederman
2022-07-20 16:50                       ` [PATCH 1/2] signal: Move stopping for the coredump from do_exit into get_signal Eric W. Biederman
2022-07-20 16:51                       ` [PATCH 2/2] coredump: Allow coredumps to pipes to work with io_uring Eric W. Biederman
2022-08-22 21:16                         ` Olivier Langlois
2022-08-23  3:35                           ` Olivier Langlois
2022-08-23 18:22                             ` Eric W. Biederman
2022-08-23 18:27                               ` Jens Axboe
2022-08-24 15:11                                 ` Eric W. Biederman
2022-08-24 15:51                                   ` Jens Axboe
2022-01-05 19:39           ` [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL Olivier Langlois

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