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From: Siddh Raman Pant via Linux-kernel-mentees <linux-kernel-mentees@lists.linuxfoundation.org>
To: "Greg KH" <gregkh@linuxfoundation.org>
Cc: syzbot+c70d87ac1d001f29a058
	<syzbot+c70d87ac1d001f29a058@syzkaller.appspotmail.com>,
	linux-kernel-mentees
	<linux-kernel-mentees@lists.linuxfoundation.org>,
	linux-security-modules <linux-security-module@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	Eric Dumazet <edumazet@google.com>,
	Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
	"Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Subject: Re: [PATCH] kernel/watch_queue: Make pipe NULL while clearing watch_queue
Date: Sat, 23 Jul 2022 19:59:23 +0530	[thread overview]
Message-ID: <1822b768504.1d4e377e236061.5518350412857967240@siddh.me> (raw)
In-Reply-To: <Ytv/4Tljvlt0PJ2r@kroah.com>

On Sat, 23 Jul 2022 19:34:17 +0530  Greg KH <gregkh@linuxfoundation.org> wrote:
> Also you now have a spinlock held when calling rcu_read_unlock(), are
> you sure that's ok?
> 
> 

We logically should not do write operations in a read critical section, so the
nulling of `wqueue->pipe->watch_queue` should happen after rcu_read_unlock().
Also, since we already have a spinlock, we can use it to ensure the nulling.
So I think it is okay.

Though, it is my first time encountering a spinlock and an rcu lock together,
so if I am wrong, please do correct me.

Thanks,
Siddh
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https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

WARNING: multiple messages have this Message-ID (diff)
From: Siddh Raman Pant <code@siddh.me>
To: "Greg KH" <gregkh@linuxfoundation.org>
Cc: "David Howells" <dhowells@redhat.com>,
	"Christophe JAILLET" <christophe.jaillet@wanadoo.fr>,
	"Eric Dumazet" <edumazet@google.com>,
	"Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
	"linux-security-modules" <linux-security-module@vger.kernel.org>,
	"linux-kernel-mentees" 
	<linux-kernel-mentees@lists.linuxfoundation.org>,
	"linux-kernel" <linux-kernel@vger.kernel.org>,
	"syzbot+c70d87ac1d001f29a058" 
	<syzbot+c70d87ac1d001f29a058@syzkaller.appspotmail.com>
Subject: Re: [PATCH] kernel/watch_queue: Make pipe NULL while clearing watch_queue
Date: Sat, 23 Jul 2022 19:59:23 +0530	[thread overview]
Message-ID: <1822b768504.1d4e377e236061.5518350412857967240@siddh.me> (raw)
In-Reply-To: <Ytv/4Tljvlt0PJ2r@kroah.com>

On Sat, 23 Jul 2022 19:34:17 +0530  Greg KH <gregkh@linuxfoundation.org> wrote:
> Also you now have a spinlock held when calling rcu_read_unlock(), are
> you sure that's ok?
> 
> 

We logically should not do write operations in a read critical section, so the
nulling of `wqueue->pipe->watch_queue` should happen after rcu_read_unlock().
Also, since we already have a spinlock, we can use it to ensure the nulling.
So I think it is okay.

Though, it is my first time encountering a spinlock and an rcu lock together,
so if I am wrong, please do correct me.

Thanks,
Siddh

  reply	other threads:[~2022-07-23 14:29 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-23 13:54 [PATCH] kernel/watch_queue: Make pipe NULL while clearing watch_queue Siddh Raman Pant
2022-07-23 13:54 ` Siddh Raman Pant via Linux-kernel-mentees
2022-07-23 14:03 ` Greg KH
2022-07-23 14:03   ` Greg KH
2022-07-23 14:29   ` Siddh Raman Pant via Linux-kernel-mentees
2022-07-23 14:29     ` Siddh Raman Pant
2022-07-24  3:45     ` Khalid Masum
2022-07-24  3:45       ` Khalid Masum
2022-07-24  4:02       ` Siddh Raman Pant
2022-07-24  4:02         ` Siddh Raman Pant via Linux-kernel-mentees
2022-07-23 14:04 ` Greg KH
2022-07-23 14:04   ` Greg KH
2022-07-23 14:29   ` Siddh Raman Pant via Linux-kernel-mentees [this message]
2022-07-23 14:29     ` Siddh Raman Pant
2022-07-27 14:46   ` David Howells
2022-07-27 14:46     ` David Howells
2022-07-27 16:20     ` Siddh Raman Pant
2022-07-27 16:20       ` Siddh Raman Pant via Linux-kernel-mentees
2022-07-31 18:11       ` Dipanjan Das
2022-07-31 18:11         ` Dipanjan Das
2022-07-31 18:46         ` Siddh Raman Pant
2022-07-31 18:46           ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-01  8:47           ` Greg KH
2022-08-01  8:47             ` Greg KH
2022-08-01  8:53             ` Siddh Raman Pant
2022-08-01  8:53               ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-01 21:06           ` Hillf Danton
2022-08-02  1:14             ` Siddh Raman Pant
2022-08-02  1:19             ` Siddh Raman Pant
2022-07-27 14:15 ` David Howells
2022-07-27 14:15   ` David Howells
2022-07-27 14:23   ` Siddh Raman Pant
2022-07-27 14:23     ` Siddh Raman Pant via Linux-kernel-mentees
2022-08-01 12:15 Hillf Danton
2022-08-01 12:52 ` Siddh Raman Pant
2022-08-01 12:52   ` Siddh Raman Pant via Linux-kernel-mentees

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