linux-kernel - Re: [PATCH] vhost-vdpa: honor CAP_IPC

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Message-ID: <20210302044918-mutt-send-email-mst@kernel.org>
Date:   Tue, 2 Mar 2021 04:51:23 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vhost-vdpa: honor CAP_IPC_LOCK

On Tue, Mar 02, 2021 at 04:14:18AM -0500, Jason Wang wrote:
> When CAP_IPC_LOCK is set we should not check locked memory against
> rlimit as what has been implemented in mlock().
> 
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Indeed and it's not just mlock.

Documentation/admin-guide/perf-security.rst:

RLIMIT_MEMLOCK and perf_event_mlock_kb resource constraints are ignored
for processes with the CAP_IPC_LOCK capability.

and let's add a Fixes: tag?

> ---
>  drivers/vhost/vdpa.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index ef688c8c0e0e..e93572e2e344 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -638,7 +638,8 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
>  	mmap_read_lock(dev->mm);
>  
>  	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> -	if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
> +	if (!capable(CAP_IPC_LOCK) &&
> +	    (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit)) {
>  		ret = -ENOMEM;
>  		goto unlock;
>  	}
> -- 
> 2.18.1