CVE-2026-99081 Longitud de mapeo DMA incorrecta para paquetes pequeños con relleno en bnxt_en

Qué es CVE-2026-99081

Los paquetes menores a BNXT_MIN_PKT_SIZE se rellenan, pero la longitud de mapeo DMA no se ajustaba, provocando lecturas DMA fuera de límites, fallas del IOMMU Intel y timeouts de la cola de transmisión en NICs BCM57412. Se corrige la longitud de mapeo DMA para paquetes pequeños con relleno.

Productos y versiones afectadas

• Linux

  • desde c0c050c58d840994ba842ad1c338a98e7c12b764 hasta antes de cf8530a25ae92c4493e2f22981ecb46f0b66f4c8
  • desde c0c050c58d840994ba842ad1c338a98e7c12b764 hasta antes de 2956aca14dd2977cd08bd2ccafae3beb8b84b268
  • desde c0c050c58d840994ba842ad1c338a98e7c12b764 hasta antes de fbd977e513971ccb4f0762a7f59eac500e474f89
  • desde c0c050c58d840994ba842ad1c338a98e7c12b764 hasta antes de 5213f65a9667d3dd85db2e6df8f2e0516290db34
  • desde c0c050c58d840994ba842ad1c338a98e7c12b764 hasta antes de a51d233ccd4889aadb71dace863525cc2b00271e

• Linux

  • 4.4

Qué hacer

1. Verificá si usás Linux y en qué versión: el rango afectado figura arriba.
2. Actualizá a la versión corregida que indique el fabricante en su aviso (ver referencias) o aplicá la mitigación que publique.
3. Revisá registros y accesos de los sistemas expuestos para descartar que se haya aprovechado antes de corregir.

Calculadora CVSS

CVSS 3.1 · 7.5 ALTA

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

VECTOR DE ATAQUE (AV)

Red

COMPLEJIDAD DEL ATAQUE (AC)

Baja

PRIVILEGIOS REQUERIDOS (PR)

Ninguno

INTERACCIÓN DEL USUARIO (UI)

Ninguna

ALCANCE (S)

Sin cambio

CONFIDENCIALIDAD (C)

Ninguna

INTEGRIDAD (I)

Ninguna

DISPONIBILIDAD (A)

Alta

Abrir la calculadora completa →

Descripción original

In the Linux kernel, the following vulnerability has been resolved: bnxt_en: fix DMA mapping length for padded small packets Stefan Fleischmann reported Intel IOMMU DMA Read faults on BCM57412 NetXtreme-E NICs when transmitting packets on VLAN/macvlan interfaces: DMAR: [DMA Read NO_PASID] Request device [18:00.0] fault addr 0xfc499000 [fault reason 0x06] PTE Read access is not set bnxt_en 0000:18:00.0 eno1np0: Abandoning msg {0xb4 0x41a} len: 0 due to firmware status: 0x2000001 ... NETDEV WATCHDOG: eno1np0 (bnxt_en): transmit queue 0 timed out The fault address (0xfc499000) is on an exact 4KB page boundary, pointing to a DMA read buffer overrun. In bnxt_start_xmit(), packets smaller than BNXT_MIN_PKT_SIZE (52 bytes), such as 42-byte untagged ARP frames, are padded: if (length < BNXT_MIN_PKT_SIZE) { pad = BNXT_MIN_PKT_SIZE - length; if (skb_pad(skb, pad)) goto tx_kick_pending; length = BNXT_MIN_PKT_SIZE; } mapping = dma_map_single(&pdev->dev, skb->data, len, DMA_TO_DEVICE); ... dma_unmap_len_set(tx_buf, len, len); However, 'len' was initialized earlier to skb_headlen(skb) (e.g. 42 bytes) and is left unadjusted after padding. Consequently, dma_map_single() and dma_unmap_len_set() map and track only 42 bytes. Later, the hardware TX buffer descriptor is programmed with the padded length: txbd->tx_bd_len_flags_type = cpu_to_le32(((len + pad) << TX_BD_LEN_SHIFT) | flags | TX_BD_FLAGS_PACKET_END); The NIC DMA engine is thus instructed to read 52 bytes from a region where only 42 bytes were DMA-mapped. If skb->data ends near the boundary of a 4KB page (within 'pad' bytes of the next page), the hardware DMA read overruns into the unmapped adjacent page, triggering an IOMMU fault. This issue was exposed after commit 447cbe95ebb9 ("vlan: fix skb_under_panic and races when toggling HW VLAN offload") because reserving extra VLAN headroom rounded LL_RESERVED_SPACE from 48 up to 64 bytes, shifting skb->data offsets and potentially causing small frames to land right against page boundaries. Fix this by using skb_put_padto(skb, BNXT_MIN_PKT_SIZE) in bnxt_start_xmit(), before skb_shinfo(skb)->nr_frags is sampled, because padding might linearize the skb. This ensures skb->len and skb_headlen(skb) reflect the padded size so that dma_map_single() maps the full buffer and the descriptor length is consistent. This also removes the temporary 'pad' variable and masking logic. The padding is done after the SW USO branch, otherwise bnxt_sw_udp_gso_xmit() would account the padding as UDP payload and send it in extra segments. Note that SW USO segments are still not padded: with IPv4, a segment carrying less than 10 bytes of UDP payload (small gso_size, or a short last segment) is sent as a frame shorter than BNXT_MIN_PKT_SIZE. This is a separate issue, left for a followup patch.

Referencias

• git.kernel.org/stable/c/cf8530a25ae92c4493e2f22981ecb46f0b66f4c8
• git.kernel.org/stable/c/2956aca14dd2977cd08bd2ccafae3beb8b84b268
• git.kernel.org/stable/c/fbd977e513971ccb4f0762a7f59eac500e474f89
• git.kernel.org/stable/c/5213f65a9667d3dd85db2e6df8f2e0516290db34
• git.kernel.org/stable/c/a51d233ccd4889aadb71dace863525cc2b00271e

Historial de la alerta

1. 23 OCT · 10:15VULNERABILIDAD Nueva vulnerabilidad detectada.

CÓMO SE HIZOResumen traducido automáticamente al español a partir de la descripción original. Ante dudas, la descripción original y las referencias del fabricante son la fuente de verdad. Cómo funciona.