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-rw-r--r--fs/cifs/smb2pdu.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index d499ce265c3b..6f0e6343c15e 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -656,15 +656,22 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
/*
* validation ioctl must be signed, so no point sending this if we
- * can not sign it. We could eventually change this to selectively
+ * can not sign it (ie are not known user). Even if signing is not
+ * required (enabled but not negotiated), in those cases we selectively
* sign just this, the first and only signed request on a connection.
- * This is good enough for now since a user who wants better security
- * would also enable signing on the mount. Having validation of
- * negotiate info for signed connections helps reduce attack vectors
+ * Having validation of negotiate info helps reduce attack vectors.
*/
- if (tcon->ses->server->sign == false)
+ if (tcon->ses->session_flags & SMB2_SESSION_FLAG_IS_GUEST)
return 0; /* validation requires signing */
+ if (tcon->ses->user_name == NULL) {
+ cifs_dbg(FYI, "Can't validate negotiate: null user mount\n");
+ return 0; /* validation requires signing */
+ }
+
+ if (tcon->ses->session_flags & SMB2_SESSION_FLAG_IS_NULL)
+ cifs_dbg(VFS, "Unexpected null user (anonymous) auth flag sent by server\n");
+
vneg_inbuf.Capabilities =
cpu_to_le32(tcon->ses->server->vals->req_capabilities);
memcpy(vneg_inbuf.Guid, tcon->ses->server->client_guid,