[PATCH proxmox-backup v4 09/14] datastore: add additional check for device number on lock helper

[Christian Ebner <c.ebner@proxmox.com>]

Comparing the inodes previous and after locking the file is not
guaranteed to protect against overmounting by another filesystem.

Further restrict by also comparing the device number to assure
uniqueness.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
 pbs-datastore/src/lib.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pbs-datastore/src/lib.rs b/pbs-datastore/src/lib.rs
index e936c7edf..5e6dca4ab 100644
--- a/pbs-datastore/src/lib.rs
+++ b/pbs-datastore/src/lib.rs
@@ -267,8 +267,9 @@ where
     let lock = lock_fn(path)?;
 
     let inode = nix::sys::stat::fstat(lock.as_raw_fd())?.st_ino;
+    let dev = nix::sys::stat::fstat(lock.as_raw_fd())?.st_dev;
 
-    if nix::sys::stat::stat(path).map_or(true, |st| inode != st.st_ino) {
+    if nix::sys::stat::stat(path).map_or(true, |st| inode != st.st_ino || dev != st.st_dev) {
         bail!("could not acquire lock, another thread modified the lock file");
     }
 
-- 
2.47.3