RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp

Overview

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

RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp

rxe_qp_from_attr() handles IB_QP_MAX_DEST_RD_ATOMIC outside the IB_QP_STATE path, so it holds no state_lock and runs while the responder task rxe_receiver() (recv_task on rxe_wq) is live. A modify_qp() setting only that attribute calls free_rd_atomic_resources() then alloc_rd_atomic_resources(), swapping qp->resp.resources[] while rxe_prepare_res()/find_resource() walk it; free_rd_atomic_resources() also leaves the cached pointer qp->resp.res dangling. A local unprivileged user can race the free/realloc into a use-after-free in rxe_receiver() (local DoS).

Drain recv_task around the swap with rxe_disable_task()/rxe_enable_task(), as rxe_qp_reset() already does when tearing this array down, re-enabling only after alloc_rd_atomic_resources() succeeds so the responder never resumes against a NULL qp->resp.resources on the ENOMEM path. Also clear qp->resp.res in free_rd_atomic_resources(), like the rxe_resp.c completion paths.

Reproduced under KASAN; the slab-use-after-free in rxe_receiver() is gone.

Affected

• Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 0136b528b753c5a56e4d997ef20b86bb6750b8fb
• Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < ffa4f0be69656be1755090f02db38d49816585c6
• Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < d4cd32eb8bd2b0ffbdc7b1f3d82ce6a371f8f844
• Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 60dfd47929cd1e7070daa810d40ce538d888410d
• Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 6f7014237405e7f032b5c53a82d9eccf6161c291
• Linux 4.8

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.