From: Omar Sandoval <osandov@osandov.com>
To: dsterba@suse.cz, linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 5/7] Btrfs: fix suspicious RCU in BTRFS_IOC_DEV_INFO
Date: Thu, 7 Sep 2017 10:24:53 -0700 [thread overview]
Message-ID: <20170907172453.GB17057@vader.DHCP.thefacebook.com> (raw)
In-Reply-To: <20170906153728.GW31874@twin.jikos.cz>
On Wed, Sep 06, 2017 at 05:37:28PM +0200, David Sterba wrote:
> On Tue, Aug 22, 2017 at 11:46:03PM -0700, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> >
> > A naked read of the value of an RCU pointer isn't safe. Put the whole
> > access in an RCU critical section, not just the pointer dereference.
>
> In this case it is safe, as the device will not go away (and potentially
> free dev->name) because it's under the device_list_mutex.
>
> The locking around devices and related structures is not exactly
> straightforward, but here I don't think we need to stick to the RCU
> pattern if the protection is guaranteed by other means. This applies to
> uuid_mutex and device_list_mutex.
You're right, it's a little confusing because uuid_mutex protects
device->name, so under device_list_mutex, device->name might change but
will never become NULL. We can just drop this one, thanks!
next prev parent reply other threads:[~2017-09-07 17:24 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-23 6:45 [PATCH 0/7] Btrfs: bugs found by sparse and RCU strings Omar Sandoval
2017-08-23 6:45 ` [PATCH 1/7] Btrfs: fix blk_status_t/errno confusion Omar Sandoval
2017-08-23 15:50 ` David Sterba
2017-08-23 16:13 ` Liu Bo
2017-08-23 19:18 ` Omar Sandoval
2017-08-23 6:46 ` [PATCH 2/7] Btrfs: fix incorrect {node,sector}size endianness from BTRFS_IOC_FS_INFO Omar Sandoval
2017-09-06 14:51 ` David Sterba
2017-08-23 6:46 ` [PATCH 3/7] Move Btrfs RCU string to common library Omar Sandoval
2017-09-06 15:15 ` David Sterba
2017-09-07 17:10 ` Omar Sandoval
2017-08-23 6:46 ` [PATCH 4/7] Btrfs: refactor btrfs_device->name updates Omar Sandoval
2017-08-23 6:46 ` [PATCH 5/7] Btrfs: fix suspicious RCU in BTRFS_IOC_DEV_INFO Omar Sandoval
2017-09-06 15:37 ` David Sterba
2017-09-07 17:24 ` Omar Sandoval [this message]
2017-08-23 6:46 ` [PATCH 6/7] Btrfs: make some volumes.c functions static Omar Sandoval
2017-09-06 15:25 ` David Sterba
2017-08-23 6:46 ` [PATCH 7/7] Btrfs: fix __user casting in ioctl.c Omar Sandoval
2017-09-06 15:23 ` David Sterba
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