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From: Nikolay Aleksandrov <>
To: Nikolay Aleksandrov <>,
	Hillf Danton <>
Subject: Re: [PATCH net-next 1/3] net: bridge: fix ioctl locking
Date: Thu, 5 Aug 2021 12:29:34 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 05/08/2021 11:29, Nikolay Aleksandrov wrote:
> From: Nikolay Aleksandrov <>
> Before commit ad2f99aedf8f ("net: bridge: move bridge ioctls out of
> .ndo_do_ioctl") the bridge ioctl calls were divided in two parts:
> one was deviceless called by sock_ioctl and didn't expect rtnl to be held,
> the other was with a device called by dev_ifsioc() and expected rtnl to be
> held. After the commit above they were united in a single ioctl stub, but
> it didn't take care of the locking expectations.
> For sock_ioctl now we acquire  (1) br_ioctl_mutex, (2) rtnl
> and for dev_ifsioc we acquire  (1) rtnl,           (2) br_ioctl_mutex
> The fix is to get a refcnt on the netdev for dev_ifsioc calls and drop rtnl
> then to reacquire it in the bridge ioctl stub after br_ioctl_mutex has
> been acquired. That will avoid playing locking games and make the rules
> straight-forward: we always take br_ioctl_mutex first, and then rtnl.
> Reported-by:
> Fixes: ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl")
> Signed-off-by: Nikolay Aleksandrov <>
> ---
>  net/bridge/br_if.c    |  4 +---
>  net/bridge/br_ioctl.c | 37 ++++++++++++++++++++++++-------------
>  net/core/dev_ioctl.c  |  7 ++++++-
>  3 files changed, 31 insertions(+), 17 deletions(-)

I fixed the bridge side of things, but the unlock/lock suggestion was made first by Hillf.
I forgot to add:

Suggested-by: Hillf Danton <>

+CC Hillf

Hillf, since the rtnl unlock/lock suggestion was yours feel free to add
your signed-off-by


  reply	other threads:[~2021-08-05  9:29 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05  8:29 [PATCH net-next 0/3] net: bridge: fix recent ioctl changes Nikolay Aleksandrov
2021-08-05  8:29 ` [PATCH net-next 1/3] net: bridge: fix ioctl locking Nikolay Aleksandrov
2021-08-05  9:29   ` Nikolay Aleksandrov [this message]
2021-08-05  8:29 ` [PATCH net-next 2/3] net: bridge: fix ioctl old_deviceless bridge argument Nikolay Aleksandrov
2021-08-05  8:29 ` [PATCH net-next 3/3] net: core: don't call SIOCBRADD/DELIF for non-bridge devices Nikolay Aleksandrov
2021-08-05 10:40 ` [PATCH net-next 0/3] net: bridge: fix recent ioctl changes patchwork-bot+netdevbpf

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