From: Christoph Hellwig <hch@lst.de>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
viro@zeniv.linux.org.uk, jack@suse.cz, dmonakhov@openvz.org,
linux-fsdevel@vger.kernel.org, linux-aio@kvack.org,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Oleg Nesterov <oleg@redhat.com>,
Mikulas Patocka <mpatocka@redhat.com>
Subject: Re: [PATCH] aio: fix a use after free (and fix freeze protection of aio writes)
Date: Mon, 17 Oct 2016 20:55:52 +0200 [thread overview]
Message-ID: <20161017185552.GA24653@lst.de> (raw)
In-Reply-To: <x49twcabzy4.fsf@segfault.boston.devel.redhat.com>
On Mon, Oct 17, 2016 at 02:19:47PM -0400, Jeff Moyer wrote:
> This ends up being a call to __sb_end_write:
>
> void __sb_end_write(struct super_block *sb, int level)
> {
> percpu_up_read(sb->s_writers.rw_sem + level-1);
> }
>
> Nothing guarantees that submission and completion happen on the same
> CPU. Is this safe?
Good point. From my reading of the percpu_rwsem implementation it
is not safe to release it from a different CPU. Which makes me
wonder how we can protect aio writes properly here..
next prev parent reply other threads:[~2016-10-17 18:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-16 5:51 [PATCH] aio: fix a use after free (and fix freeze protection of aio writes) Christoph Hellwig
2016-10-17 18:19 ` Jeff Moyer
2016-10-17 18:55 ` Christoph Hellwig [this message]
2016-10-17 19:40 ` Jeff Moyer
2016-10-17 19:54 ` Peter Zijlstra
2016-10-17 20:04 ` Jeff Moyer
2016-10-17 20:04 ` Christoph Hellwig
2016-10-17 19:54 ` Peter Zijlstra
2016-10-17 20:05 ` Jeff Moyer
2016-10-24 6:36 ` Christoph Hellwig
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