linux-kernel - RE: [PATCH] Drivers: hv: kvp/vss: Avoid accessing a ringbuffer not initialized yet

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <SA1PR21MB131794D6AF620CB201958EFCBF542@SA1PR21MB1317.namprd21.prod.outlook.com>
Date: Wed, 30 Oct 2024 19:03:31 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: Michael Kelley <mhklinux@...look.com>, KY Srinivasan <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Vitaly
 Kuznetsov <vkuznets@...hat.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, "open list:Hyper-V/Azure CORE AND DRIVERS"
	<linux-hyperv@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
CC: "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] Drivers: hv: kvp/vss: Avoid accessing a ringbuffer not
 initialized yet

> From: Michael Kelley <mhklinux@...look.com>
> Sent: Tuesday, October 29, 2024 4:45 PM
> [...]
> An alternate approach occurs to me. util_probe() does these three
> things in order:
> 
> 1) Allocates the receive buffer
> 2) Calls the util_init() function, which for KVP and VSS creates the char dev
> 3) Sets up the VMBus channel, including calling vmbus_open()
> 
> What if the order of #2 and #3 were swapped in util_probe()? I
> don't immediately see any interdependency between #2 and #3
> for KVP and VSS, nor for Shutdown and Timesync. With the swap,
> the VMBus channel would be fully open by the time the /dev entry
> appears and the user space daemon can do anything.
> 
> I haven't though too deeply about this, so maybe there's a problem
> somewhere. But if not, it seems a lot cleaner.
> 
> Michael

I think #3 depends on #2, e.g. hv_kvp_init() sets the channel's
preferred max_pkt_size, which is tested later in __vmbus_open().

Another example of dependency is: hv_timesync_init() initializes
host_ts.lock and adj_time_work, which are used by
timesync_onchannelcallback() -> adj_guesttime().
Note: the channel callback can be already running before
vmbus_open() returns.

Thanks,
Dexuan