net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry

Summary

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry With AF_XDP on a striding RQ, mlx5e defers releasing XSK buffers until an MPWQE is refilled. If XSK allocation then returns -ENOMEM, actual_wq_head is not advanced and a later NAPI poll retries the same WQE. mlx5e_free_rx_mpwqe() leaves each released slot marked as releasable. On retry it can therefore call xsk_buff_free() again through stale pointers after the frames have returned to the XSK pool and been reallocated. Set all skip_release_bitmap bits in the common error path of mlx5e_xsk_alloc_rx_mpwqe(). This matches mlx5e_alloc_rx_mpwqe(). A successful allocation already clears the bitmap after replacing every buffer, so retries become idempotent without changing the success path. Fault injection forced three consecutive failures for one selected MPWQE. Both an early allocation failure and a partial 8-of-16-buffer unwind released the original 16 XSK buffers only once. Each error left a full bitmap, the following NAPI retry skipped the release, and a later successful allocation cleared it. A 20-second AF_XDP zero-copy pressure run exercised 1,575,262 buffer allocation failures without invalid descriptors, WQE errors, or kernel warnings.

Affected versions

• Linux Linux

  From 4c2a1323680709078736a2886c754004e9fe42e6 · fixed in f3a52e2ec2788a7f6b64137985c087188a54ad4f; From 4c2a1323680709078736a2886c754004e9fe42e6 · fixed in d215d09606b0fcd18ad1eb532995782a21cea49d; From 4c2a1323680709078736a2886c754004e9fe42e6 · fixed in 867119b4b588037724b85839d534465f0334d9bd; From 4c2a1323680709078736a2886c754004e9fe42e6 · fixed in 3d73a1164a8c6b4461907a65cb6c022ea4fd39af; From 4c2a1323680709078736a2886c754004e9fe42e6 · fixed in 63811edf512584c946e5e96b100e9e280703bbb5

• Linux Linux

  6.4

• KernelLinux

  From 6.4.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.113; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.2.11

References 5