net: stmmac: fix TX descriptor availability check for TSO traffic

Summary

In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix TX descriptor availability check for TSO traffic stmmac_tso_xmit() estimates the number of free TX descriptors required by a TSO skb as: (skb->len - proto_hdr_len) / TSO_MAX_BUFF_SIZE + 1 which assumes the payload is split into TSO_MAX_BUFF_SIZE chunks. This underestimates the descriptors actually consumed by stmmac_tso_allocator(), since each fragment is mapped individually and so it needs at least one descriptor regardless of its size. Moreover, one descriptor is used for the L2/L3/L4 headers and, when the MSS changes, one more is consumed for the MSS context descriptor. For a highly fragmented TSO skb the check can therefore pass even when the ring has too few free slots. stmmac_tso_allocator() then writes past the available descriptors, overwriting descriptors still owned by the DMA engine, corrupting the TX ring. Add stmmac_tso_get_num_desc() to compute the exact number of descriptors needed for the header, the linear payload and each fragment, plus the MSS context descriptor when required, and use it in the availability check.

Timeline

1. Sep 25, 2026, 10:23 AM UTCCVE published
2. Oct 21, 2026, 12:53 PM UTCRecord last updated

Affected versions

• Linux Linux

  From f748be531d7012c456b97f66091d86b3675c5fef · fixed in 09c30547da2c45bb79f7d3adffc860af332c2d42; From f748be531d7012c456b97f66091d86b3675c5fef · fixed in ffa6d2481bc1c87f822ecd626561484e4ee24cef; From f748be531d7012c456b97f66091d86b3675c5fef · fixed in c28175220f808c867d5618de8ecc6dbcc815c773; From f748be531d7012c456b97f66091d86b3675c5fef · fixed in 65820fc743eae322f7f94f6a64d07861211d4b21; From f748be531d7012c456b97f66091d86b3675c5fef · fixed in 5e38d732ec67a5b1f9a56e6c73add480c4b6030a

• Linux Linux

  4.7

• KernelLinux

  From 4.7.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.111; From 6.13.0 · fixed in 6.18.53; From 6.19.0 · fixed in 7.2.7

References 5