linux-kernel - Re: [PATCH] io_uring/kbuf: Fix size for shared buffer ring

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Date:   Thu, 27 Apr 2023 08:35:06 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Tudor Cretu <tudor.cretu@....com>, io-uring@...r.kernel.org
Cc:     =axboe@...nel.dk, asml.silence@...il.com, kevin.brodsky@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] io_uring/kbuf: Fix size for shared buffer ring

On 4/27/23 8:31?AM, Tudor Cretu wrote:
> The size of the ring is the product of ring_entries and the size of
> struct io_uring_buf. Using struct_size is equivalent to
>   (ring_entries + 1) * sizeof(struct io_uring_buf)
> and generates an off-by-one error. Fix it by using size_mul directly.

Looks right, so we're doing one entry too much. This is probably a
remnant of when the initial version had it done a bit differently, but
we overlaid the tail with the first entry reserved field.

-- 
Jens Axboe