Bug 1224496 (CVE-2024-35902)

In the Linux kernel, the following vulnerability has been resolved:

net/rds: fix possible cp null dereference

cp might be null, calling cp->cp_conn would produce null dereference

[Simon Horman adds:]

Analysis:

* cp is a parameter of __rds_rdma_map and is not reassigned.

* The following call-sites pass a NULL cp argument to __rds_rdma_map()

  - rds_get_mr()
  - rds_get_mr_for_dest

* Prior to the code above, the following assumes that cp may be NULL
  (which is indicative, but could itself be unnecessary)

	trans_private = rs->rs_transport->get_mr(
		sg, nents, rs, &mr->r_key, cp ? cp->cp_conn : NULL,
		args->vec.addr, args->vec.bytes,
		need_odp ? ODP_ZEROBASED : ODP_NOT_NEEDED);

* The code modified by this patch is guarded by IS_ERR(trans_private),
  where trans_private is assigned as per the previous point in this analysis.

  The only implementation of get_mr that I could locate is rds_ib_get_mr()
  which can return an ERR_PTR if the conn (4th) argument is NULL.

* ret is set to PTR_ERR(trans_private).
  rds_ib_get_mr can return ERR_PTR(-ENODEV) if the conn (4th) argument is NULL.
  Thus ret may be -ENODEV in which case the code in question will execute.

Conclusion:
* cp may be NULL at the point where this patch adds a check;
  this patch does seem to address a possible bug

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-35902
https://www.cve.org/CVERecord?id=CVE-2024-35902
https://git.kernel.org/stable/c/62fc3357e079a07a22465b9b6ef71bb6ea75ee4b
https://git.kernel.org/stable/c/6794090c742008c53b344b35b021d4a3093dc50a
https://git.kernel.org/stable/c/92309bed3c5fbe2ccd4c45056efd42edbd06162d
https://git.kernel.org/stable/c/bcd46782e2ec3825d10c1552fcb674d491cc09f9
https://git.kernel.org/stable/c/cbaac2e5488ed54833897264a5ffb2a341a9f196
https://git.kernel.org/stable/c/cfb786b03b03c5ff38882bee38525eb9987e4d14
https://git.kernel.org/stable/c/d275de8ea7be3a453629fddae41d4156762e814c
https://git.kernel.org/stable/c/d49fac38479bfdaec52b3ea274d290c47a294029
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-35902.mbox