CVE-2024-35902 — net/rds: fix possible cp null dereference

Affected: Linux, Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

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

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CVE-2024-35902 — net/rds: fix possible cp null dereference