net/mlx5e: Fix handling of compressed CQEs in case of low NAPI budget
When CQE compression is enabled, compressed CQEs use the following
structure: a title is followed by one or many blocks, each containing 8
mini CQEs (except the last, which may contain fewer mini CQEs).
Due to NAPI budget restriction, a complete structure is not always
parsed in one NAPI run, and some blocks with mini CQEs may be deferred
to the next NAPI poll call - we have the mlx5e_decompress_cqes_cont call
in the beginning of mlx5e_poll_rx_cq. However, if the budget is
extremely low, some blocks may be left even after that, but the code
that follows the mlx5e_decompress_cqes_cont call doesn't check it and
assumes that a new CQE begins, which may not be the case. In such cases,
random memory corruptions occur.
An extremely low NAPI budget of 8 is used when busy_poll or busy_read is
active.
This commit adds a check to make sure that the previous compressed CQE
has been completely parsed after mlx5e_decompress_cqes_cont, otherwise
it prevents a new CQE from being fetched in the middle of a compressed
CQE.
This commit fixes random crashes in __build_skb, __page_pool_put_page
and other not-related-directly places, that used to happen when both CQE
compression and busy_poll/busy_read were enabled.
projects / kernel.git / commit