net: spacemit: clear TX descriptor on fragment mapping failure

Overview

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

• Linux >= bfec6d7f2001c7470c3cd261ae65a3ba8737f226 < ca9986cc824f2feb79b4a83e5f6f4c24c2140448
• Linux >= bfec6d7f2001c7470c3cd261ae65a3ba8737f226 < 3001a103a367c6051c43aff363b6979c10e65347
• Linux >= bfec6d7f2001c7470c3cd261ae65a3ba8737f226 < 2d14720beb58870b15a52b236c3ab0be0e06e915
• Linux 6.18

Remediation

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