CVE-2026-99078: net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry

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

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

With AFXDP on a striding RQ, mlx5e defers releasing XSK buffers until an MPWQE is refilled. If XSK allocation then returns -ENOMEM, actualwqhead is not advanced and a later NAPI poll retries the same WQE.

mlx5efreerxmpwqe() leaves each released slot marked as releasable. On retry it can therefore call xskbufffree() again through stale pointers after the frames have returned to the XSK pool and been reallocated.

Set all skipreleasebitmap bits in the common error path of mlx5exskallocrxmpwqe(). This matches mlx5eallocrxmpwqe(). 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 AFXDP zero-copy pressure run exercised 1,575,262 buffer allocation failures without invalid descriptors, WQE errors, or kernel warnings.