From: Jiri Kosina <jikos@kernel.org>
To: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Gary King <gary.king@oculus.com>, linux-input@vger.kernel.org
Subject: Re: [PATCH] hidraw: fix list->buffer race condition
Date: Fri, 7 Oct 2016 10:43:55 +0200 (CEST) [thread overview]
Message-ID: <alpine.LNX.2.00.1610071043080.31629@cbobk.fhfr.pm> (raw)
In-Reply-To: <20161005075329.GZ19261@mail.corp.redhat.com>
On Wed, 5 Oct 2016, Benjamin Tissoires wrote:
> > @@ -98,7 +99,9 @@ static ssize_t hidraw_read(struct file *file, char __user *buffer, size_t count,
> >
> > kfree(list->buffer[list->tail].value);
> > list->buffer[list->tail].value = NULL;
> > + smp_wmb();
> > list->tail = (list->tail + 1) & (HIDRAW_BUFFER_SIZE - 1);
> > + smp_wmb();
>
> How does these barriers be needed? To me, list->tail gets accessed just
> before, so I doubt the compiler would decide to reorder the code without
> changing the semantic.
These are CPU barriers, not compiler barriers.
(that's just a clarification, it doesn't imply in any way that I'd think
the barriers are correct :) ).
Thanks,
--
Jiri Kosina
SUSE Labs
next prev parent reply other threads:[~2016-10-07 8:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-05 0:44 [PATCH] hidraw: fix list->buffer race condition Gary King
2016-10-05 7:53 ` Benjamin Tissoires
2016-10-07 8:43 ` Jiri Kosina [this message]
2016-10-07 8:43 ` Jiri Kosina
2016-10-07 17:30 ` Gary King
2016-10-10 8:36 ` Jiri Kosina
2016-10-11 3:12 ` Dmitry Torokhov
2016-10-14 1:29 ` Gary King
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