An ODP MR's page array map.pfn_list[] is sized from the umem's start, but rxe_check_pagefault() indexes it with an iova taken relative to that start, while the access was range-checked against the MR's iova (ibmr.iova). reg_mr only requires start and hca_va to share a page offset, so a user can register with hca_va = start + N*PAGE, and the index skew (hca_va - start) >> PAGE_SHIFT then lands out of bounds of pfn_list[], which is read with no bound check. An unprivileged local user reaches this with a single RDMA operation on a self-connected rxe QP: observed as a KASAN slab-out-of-bounds read and, when the out-of-bounds qword looks like a writable HMM pfn, a write into an attacker-influenced page. Reject an index that leaves the umem and force the fault path, which fails the out-of-range access via the umem range check in ib_umem_odp_map_dma_and_lock(). The downstream pfn_list[] users (__rxe_odp_mr_copy() and the atomic helpers) run only after a successful map, so this check protects them as well. Fixes: 2fae67ab63db ("RDMA/rxe: Add support for Send/Recv/Write/Read with ODP") Cc: stable@vger.kernel.org Signed-off-by: Youngsung Ahn Assisted-by: LLM --- Notes (not part of the commit): Reproduced on a KASAN x86-64 build of 7.3-rc4 as uid 1000; the data-only write primitive was used to reach uid 0 on a fully hardened build. drivers/infiniband/sw/rxe/ is unchanged between 7.3-rc4 (93f51579e7df) and mainline 551c722f4080 (2026-09-29) and rdma for-next, so both are affected. Compile-tested (KASAN+RDMA_RXE), not runtime-tested. Found through AI-assisted review; per Documentation/process/security-bugs.rst this is public and a reproducer can be shared on request. A maintainer may prefer to also index relative to ibmr.iova (as the non-ODP rxe_mr_iova_to_index() does) so legitimately skewed MRs keep working; this patch takes the minimal, safe route. v2: no code change. Added Assisted-by: LLM and dropped the security@kernel.org Cc, per review of v1. drivers/infiniband/sw/rxe/rxe_odp.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c index ab21b620e94c..07a30c60fc62 100644 --- a/drivers/infiniband/sw/rxe/rxe_odp.c +++ b/drivers/infiniband/sw/rxe/rxe_odp.c @@ -136,6 +136,11 @@ static inline bool rxe_check_pagefault(struct ib_umem_odp *umem_odp, u64 iova, while (addr < iova + length) { idx = (addr - ib_umem_start(umem_odp)) >> umem_odp->page_shift; + if (idx >= ib_umem_odp_num_pages(umem_odp)) { + need_fault = true; + break; + } + if ((umem_odp->map.pfn_list[idx] & access) != access) { need_fault = true; break; -- 2.43.0