CVE-2023-44466 (C, published 2023-09-29T06:15Z)
Description: value: An issue was discovered in net/ceph/messenger_v2.c in the Linux kernel before 6.4.5. There is an integer signedness error, leading to a buffer overflow and remote code execution via HELLO or one of the AUTH frames. This occurs because of an untrusted length taken from a TCP packet in ceph_decode_32.
Severity: nan (CVSS v3 base score: 8.8)
Weakness: CWE-120 \u2014 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.
Repository: https://github.com/torvalds/linux
Files changed:
net/ceph/messenger_v2.c
Commit message: libceph: harden msgr2.1 frame segment length checks

ceph_frame_desc::fd_lens is an int array.  decode_preamble() thus
effectively casts u32 -> int but the checks for segment lengths are
written as if on unsigned values.  While reading in HELLO or one of the
AUTH frames (before authentication is completed), arithmetic in
head_onwire_len() can get duped by negative ctrl_len and produce
head_len which is less than CEPH_PREAMBLE_LEN but still positive.
This would lead to a buffer overrun in prepare_read_control() as the
preamble gets copied to the newly allocated buffer of size head_len.

Cc: stable@vger.kernel.org
Fixes: cd1a677cad99 ("libceph, ceph: implement msgr2.1 protocol (crc and secure modes)")
Reported-by: Thelford Williams <thelford@google.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>


Vulnerable code:
	/*
	 * This would fire for FRAME_TAG_WAIT (it has one empty
	 * segment), but we should never get it as client.
	 */
	if (!desc->fd_lens[desc->fd_seg_cnt - 1]) {
		pr_err("last segment empty\n");

	if (desc->fd_lens[0] > CEPH_MSG_MAX_CONTROL_LEN) {
		pr_err("control segment too big %d\n", desc->fd_lens[0]);
	if (desc->fd_lens[1] > CEPH_MSG_MAX_FRONT_LEN) {
		pr_err("front segment too big %d\n", desc->fd_lens[1]);
	if (desc->fd_lens[2] > CEPH_MSG_MAX_MIDDLE_LEN) {
		pr_err("middle segment too big %d\n", desc->fd_lens[2]);
	if (desc->fd_lens[3] > CEPH_MSG_MAX_DATA_LEN) {
		pr_err("data segment too big %d\n", desc->fd_lens[3]);

Fixed code:
	BUG_ON(ctrl_len < 0 || ctrl_len > CEPH_MSG_MAX_CONTROL_LEN);

	BUG_ON(front_len < 0 || front_len > CEPH_MSG_MAX_FRONT_LEN ||
	       middle_len < 0 || middle_len > CEPH_MSG_MAX_MIDDLE_LEN ||
	       data_len < 0 || data_len > CEPH_MSG_MAX_DATA_LEN);

	if (desc->fd_lens[0] < 0 ||
	    desc->fd_lens[0] > CEPH_MSG_MAX_CONTROL_LEN) {
		pr_err("bad control segment length %d\n", desc->fd_lens[0]);
	if (desc->fd_lens[1] < 0 ||
	    desc->fd_lens[1] > CEPH_MSG_MAX_FRONT_LEN) {
		pr_err("bad front segment length %d\n", desc->fd_lens[1]);
	if (desc->fd_lens[2] < 0 ||
	    desc->fd_lens[2] > CEPH_MSG_MAX_MIDDLE_LEN) {
		pr_err("bad middle segment length %d\n", desc->fd_lens[2]);
	if (desc->fd_lens[3] < 0 ||
	    desc->fd_lens[3] > CEPH_MSG_MAX_DATA_LEN) {
		pr_err("bad data segment length %d\n", desc->fd_lens[3]);

	/*
	 * This would fire for FRAME_TAG_WAIT (it has one empty
	 * segment), but we should never get it as client.
	 */
	if (!desc->fd_lens[desc->fd_seg_cnt - 1]) {
		pr_err("last segment empty, segment count %d\n",
		       desc->fd_seg_cnt);