Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE38E2DC783; Mon, 17 Aug 2026 14:31:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786977083; cv=none; b=aZd8Gh6n/Ho0iLVEo4T1VlGpTJ5rKwKi4Kcm8152a/gxa/L8q6JmG40xNK7H6u3BWIquTSz/N8LRdUlpx5oIBypFCpx7eGwivdW8lzH5S8UEecPpEEbWI2xtyE3vmr+WAIZOStszDUGeLBtUDE7TS2g5DSWWe4s796RUHpr9BKA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786977083; c=relaxed/simple; bh=Oas7lZ48lqeWctzgOUqE79qUnlS8Cm22nHjk8M9CIAI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p3xsVh3IlNmGi3kw7+sexzJwZwFrgQ2LVqujcPx0kPYYyVX8jvVxt6BBN6K6ljeQUihrPzIRnGPI8qx3T+TdV6tDg8JOxYxEvAJnRWzmAp306+g8wkz028KzK9nlDPJL2OXc6ES5V2e6zSFA3AZzBgQHjyrtkFyQ5ytwB8ajL7s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EI1NcY/Q; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="EI1NcY/Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 22F741F000E9; Mon, 17 Aug 2026 14:31:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786977082; bh=w/zzhq0eparkovqD8CA0JJaRgFAkChNaSDGVsQrHd0s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EI1NcY/QrRlON5QXuwm/gwsdiEwLbLjb24HmGDU0sTWaPTBcC8ZnZGOM2J4fyUyvl 8KUg/wt3F0dC1cyh2RQkPY3I8ueNS14oyCGzuYDqh4UtZsS0GPYkd2Zu6UE0o5bI+k lgETibcoDRMC+R4i82kEwkpJi9+ph8qRpeQ+zx50= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Raphael Zimmer , Ilya Dryomov Subject: [PATCH 5.15 206/456] libceph: Reject monmaps advertising zero monitors Date: Mon, 17 Aug 2026 15:29:56 +0200 Message-ID: <20260817132548.191073730@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132539.792407575@linuxfoundation.org> References: <20260817132539.792407575@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Raphael Zimmer commit 40480eee361ed9676b3f844d532ac28b47251634 upstream. A message of type CEPH_MSG_MON_MAP contains a monmap that is sent from a monitor to the client. This monmap contains information about the existing monitors in the cluster. Currently, a monmap indicating that there are zero monitors in the cluster is treated as valid. However, it is impossible to have zero monitors in the cluster and still receive a valid monmap from a monitor. Therefore, such a monmap must be corrupted and should be treated as invalid. Furthermore, a monmap with a monitor count of zero can subsequently crash the client when attempting to open a session with a monitor in __open_session(). This happens because the "BUG_ON(monc->monmap->num_mon < 1)" assertion in pick_new_mon() is triggered. This patch extends a check in ceph_monmap_decode() to also reject arriving mon_maps with num_mon == 0 rather than only with num_mon > CEPH_MAX_MON. [ idryomov: drop "log output for unusual values of num_mon" part ] Cc: stable@vger.kernel.org Signed-off-by: Raphael Zimmer Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov Signed-off-by: Greg Kroah-Hartman --- net/ceph/mon_client.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ceph/mon_client.c +++ b/net/ceph/mon_client.c @@ -114,7 +114,7 @@ static struct ceph_monmap *ceph_monmap_d dout("%s fsid %pU epoch %u num_mon %u\n", __func__, &fsid, epoch, num_mon); - if (num_mon > CEPH_MAX_MON) + if (num_mon == 0 || num_mon > CEPH_MAX_MON) goto e_inval; monmap = kmalloc(struct_size(monmap, mon_inst, num_mon), GFP_NOIO);