CVE-2025-21888 — RDMA/mlx5: Fix a WARN during dereg_mr for DM type

Affected: Linux

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

RDMA/mlx5: Fix a WARN during dereg_mr for DM type

Memory regions (MR) of type DM (device memory) do not have an associated umem.

In the __mlx5_ib_dereg_mr() -> mlx5_free_priv_descs() flow, the code incorrectly takes the wrong branch, attempting to call dma_unmap_single() on a DMA address that is not mapped.

This results in a WARN [1], as shown below.

The issue is resolved by properly accounting for the DM type and ensuring the correct branch is selected in mlx5_free_priv_descs().

[1] WARNING: CPU: 12 PID: 1346 at drivers/iommu/dma-iommu.c:1230 iommu_dma_unmap_page+0x79/0x90 Modules linked in: ip6table_mangle ip6table_nat ip6table_filter ip6_tables iptable_mangle xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter rpcsec_gss_krb5 auth_rpcgss oid_registry ovelay rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm mlx5_ib ib_uverbs ib_core fuse mlx5_core CPU: 12 UID: 0 PID: 1346 Comm: ibv_rc_pingpong Not tainted 6.12.0-rc7+ #1631 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:iommu_dma_unmap_page+0x79/0x90 Code: 2b 49 3b 29 72 26 49 3b 69 08 73 20 4d 89 f0 44 89 e9 4c 89 e2 48 89 ee 48 89 df 5b 5d 41 5c 41 5d 41 5e 41 5f e9 07 b8 88 ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 66 0f 1f 44 00 RSP: 0018:ffffc90001913a10 EFLAGS: 00010…

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CVE-2025-21888 — RDMA/mlx5: Fix a WARN during dereg_mr for DM type