filelocks: use mount idmapping for setlease permission check

A user should be allowed to take out a lease via an idmapped mount if the fsuid matches the mapped uid of the inode. generic_setlease() is checking the unmapped inode uid, causing these operations to be denied. Fix this by comparing against the mapped inode uid instead of the unmapped uid. Fixes: 9caccd4 ("fs: introduce MOUNT_ATTR_IDMAP") Cc: [email protected] Signed-off-by: Seth Forshee (DigitalOcean) <[email protected]> Signed-off-by: Christian Brauner (Microsoft) <[email protected]>
sedwards · Mar 9, 2023 · 42d0c4b · 42d0c4b
1 parent dc59219
commit 42d0c4b
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/fs/locks.c b/fs/locks.c
@@ -1863,9 +1863,10 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp,
 			void **priv)
 {
 	struct inode *inode = file_inode(filp);
+	vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(filp), inode);
 	int error;
 
-	if ((!uid_eq(current_fsuid(), inode->i_uid)) && !capable(CAP_LEASE))
+	if ((!vfsuid_eq_kuid(vfsuid, current_fsuid())) && !capable(CAP_LEASE))
 		return -EACCES;
 	if (!S_ISREG(inode->i_mode))
 		return -EINVAL;