diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 7d6539a04fac..1e176e11dbfa 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1120,10 +1120,10 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
 
 	/*
 	 * Accessing maxBuf is racy with cifs_reconnect - need to store value
-	 * and check it for zero before using.
+	 * and check it before using.
 	 */
 	max_buf = tcon->ses->server->maxBuf;
-	if (!max_buf) {
+	if (max_buf < (sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE))) {
 		free_xid(xid);
 		return -EINVAL;
 	}
@@ -1460,10 +1460,10 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
 
 	/*
 	 * Accessing maxBuf is racy with cifs_reconnect - need to store value
-	 * and check it for zero before using.
+	 * and check it before using.
 	 */
 	max_buf = tcon->ses->server->maxBuf;
-	if (!max_buf)
+	if (max_buf < (sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE)))
 		return -EINVAL;
 
 	max_num = (max_buf - sizeof(struct smb_hdr)) /
diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c
index b4b1f0305f29..79078533f807 100644
--- a/fs/cifs/smb2file.c
+++ b/fs/cifs/smb2file.c
@@ -124,10 +124,10 @@ smb2_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
 
 	/*
 	 * Accessing maxBuf is racy with cifs_reconnect - need to store value
-	 * and check it for zero before using.
+	 * and check it before using.
 	 */
 	max_buf = tcon->ses->server->maxBuf;
-	if (!max_buf)
+	if (max_buf < sizeof(struct smb2_lock_element))
 		return -EINVAL;
 
 	max_num = max_buf / sizeof(struct smb2_lock_element);