Virtualization - Mar 2021 - [PATCH] vhost-vdpa: honor CAP_IPC_LOCK

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 at redhat.com>
---
 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

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 at redhat.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