Re: [PATCH v3] RDMA/mlx5: Fix CQ resize destination index mask

[sashiko-bot@kernel.org]

> From: Li RongQing <lirongqing@baidu.com>
> 
> In copy_resize_cqes, the destination CQE index is computed as
> (i + 1) & cq->resize_buf->nent, but resize_buf->nent is produced by
> roundup_pow_of_two(), so it is a power of two with exactly one bit set.
> Masking with a single-bit value can only yield 0 or nent itself. The
> buffer has nent entries, so valid indices are 0 .. nent - 1 and nent is
> one past the last slot; whenever the masked result is nent the following
> memcpy writes one entry out of bounds.
> 
> Use (nent - 1) as the wrap mask instead. For a power-of-two nent,
> (i + 1) & (nent - 1) is the correct modulo-nent reduction, keeping the
> index within [0, nent - 1]. This matches get_sw_cqe(), which addresses
> the CQ buffer via n & cq->ibcq.cqe, where cq->ibcq.cqe == entries - 1 is
> exactly the nent - 1 wrap mask.
> 
> Fixes: bde51583f49b ("IB/mlx5: Add support for resize CQ")
> Signed-off-by: Li RongQing <lirongqing@baidu.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261019050503.2313-1-lirongqing@baidu.com?part=1