[Devel] [PATCH RHEL8 COMMIT] devcgroup: Allow mounting device with no write perm for new mount api

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-305.3.1.vz8.7.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-305.3.1.vz8.7.10
------>
commit 57a85c23be1a606ee01f723aa741fe9fcdb9fe7f
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Fri Aug 27 20:32:28 2021 +0300

    devcgroup: Allow mounting device with no write perm for new mount api
    
    After rebase to RH8.4 we now have alternative code path to mount bdev
    for filesystems which switched to new mount api (e.g. checked it on
    xfs). Without this fix if block device with xfs is available in
    container and has "b major:minor rM" device cgroup allow rule for this
    container, the user inside would still not be able to mount this disk,
    which means "M" would not work.
    
    Note: we use "M" instead of "w" when we want to only allow mounting of
    the given disk but not writes to it.
    
    Fixes: 6d716d983506 ("device_cgroup: add device visibility virtualization in CT")
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 fs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/super.c b/fs/super.c
index a68ab7d3e1b7..2edab581b876 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1328,7 +1328,7 @@ int get_tree_bdev(struct fs_context *fc,
 	if (!fc->source)
 		return invalf(fc, "No source specified");
 
-	bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
+	bdev = blkdev_get_by_path(fc->source, mode | FMODE_MOUNT, fc->fs_type);
 	if (IS_ERR(bdev)) {
 		errorf(fc, "%s: Can't open blockdev", fc->source);
 		return PTR_ERR(bdev);