[pbs-devel] [RFC PATCH 5/5] fix: api: avoid race condition in set_backup_owner

[Stefan Sterz <s.sterz@proxmox.com>]

when two clients change the owner of a backup store, a race condition
arose. add locking to avoid this.

Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>
---
 src/api2/admin/datastore.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
index ef82b426..0c297937 100644
--- a/src/api2/admin/datastore.rs
+++ b/src/api2/admin/datastore.rs
@@ -1889,11 +1889,12 @@ pub fn set_backup_owner(
 
     let privs = user_info.lookup_privs(&auth_id, &["datastore", &store]);
 
+    let owner = datastore.get_owner(&backup_group)?;
+
     let allowed = if (privs & PRIV_DATASTORE_MODIFY) != 0 {
         // High-privilege user/token
         true
     } else if (privs & PRIV_DATASTORE_BACKUP) != 0 {
-        let owner = datastore.get_owner(&backup_group)?;
 
         match (owner.is_token(), new_owner.is_token()) {
             (true, true) => {
@@ -1940,6 +1941,12 @@ pub fn set_backup_owner(
               new_owner);
     }
 
+    let _guard = datastore.lock_group(&backup_group)?;
+
+    if owner != datastore.get_owner(&backup_group)? {
+        bail!("{} does not own this group anymore", owner);
+    }
+
     datastore.set_owner(&backup_group, &new_owner, true)?;
 
     Ok(())
-- 
2.30.2