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

net: spacemit: clear TX descriptor on fragment mapping failure

emac_tx_mem_map() writes TX_DESC_0_OWN into the ring descriptor for every slot beyond old_head as soon as that slot's memset()'d local copy is committed with "*tx_desc_addr = tx_desc", i.e. before the buffers for that slot have necessarily all been mapped successfully. If emac_tx_map_frag() then fails on a later fragment, the err_free_skb path calls emac_free_tx_buf() to unmap and drop the skb, but leaves the already-written descriptor memory untouched, and tx_ring->head is never advanced past old_head (the "tx_ring->head = head" store is skipped by the goto).

So a slot between old_head and the rolled-back head can be left with TX_DESC_0_OWN set and buffer_addr_{1,2} pointing at DMA mappings that emac_free_tx_buf() just tore down, while software considers that slot free again. The next successful emac_tx_mem_map() call only rebuilds old_head itself; if the DMA engine auto-advances into the following descriptor once it finishes old_head's packet, it will fetch that stale, already-unmapped address.

emac_tx_clean_desc() already treats emac_free_tx_buf() and clearing the descriptor as a pair when reclaiming completed descriptors; do the same in the mapping failure path.

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

net: spacemit: clear TX descriptor on fragment mapping failure

emac_tx_mem_map() writes TX_DESC_0_OWN into the ring descriptor for every slot beyond old_head as soon as that slot's memset()'d local copy is committed with "*tx_desc_addr = tx_desc", i.e. before the buffers for that slot have necessarily all been mapped successfully. If emac_tx_map_frag() then fails on a later fragment, the err_free_skb path calls emac_free_tx_buf() to unmap and drop the skb, but leaves the already-written descriptor memory untouched, and tx_ring->head is never advanced past old_head (the "tx_ring->head = head" store is skipped by the goto).

So a slot between old_head and the rolled-back head can be left with TX_DESC_0_OWN set and buffer_addr_{1,2} pointing at DMA mappings that emac_free_tx_buf() just tore down, while software considers that slot free again. The next successful emac_tx_mem_map() call only rebuilds old_head itself; if the DMA engine auto-advances into the following descriptor once it finishes old_head's packet, it will fetch that stale, already-unmapped address.

emac_tx_clean_desc() already treats emac_free_tx_buf() and clearing the descriptor as a pair when reclaiming completed descriptors; do the same in the mapping failure path.

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 118 more

In the Linux kernel, the following vulnerability has been resolved: net: spacemit: clear TX descriptor on fragment mapping failure emac_tx_mem_map() writes TX_DESC_0_OWN into the ring descriptor for every slot beyond old_head as soon as that slot's memset()'d local copy is committed with "*tx_desc_addr = tx_desc", i.e. before the buffers for that slot have necessarily all been mapped successfully. If emac_tx_map_frag() then fails on a later fragment, the err_free_skb path calls emac_free_tx_buf() to unmap and drop the skb, but leaves the already-written descriptor memory untouched, and tx_ring->head is never advanced past old_head (the "tx_ring->head = head" store is skipped by the goto). So a slot between old_head and the rolled-back head can be left with TX_DESC_0_OWN set and buffer_addr_{1,2} pointing at DMA mappings that emac_free_tx_buf() just tore down, while software considers that slot free again. The next successful emac_tx_mem_map() call only rebuilds old_head itself; if the DMA engine auto-advances into the following descriptor once it finishes old_head's packet, it will fetch that stale, already-unmapped address. emac_tx_clean_desc() already treats emac_free_tx_buf() and clearing the descriptor as a pair when reclaiming completed descriptors; do the same in the mapping failure path.

Ein Angreifer kann mehrere Schwachstellen im Linux Kernel ausnutzen, um einen nicht näher spezifizierten Angriff durchzuführen, möglicherweise einen Denial-of-Service-Angriff auszulösen, Daten zu manipulieren oder offenzulegen oder Sicherheitsmaßnahmen zu umgehen.