linux-kernel - Re: [PATCH][next][V2] io_uring: Fix incorrect sizeof operator for copy_from

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Message-ID: <b6790793-c6ab-5d41-d483-3f978557e904@gmail.com>
Date:   Tue, 15 Jun 2021 14:35:46 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Colin King <colin.king@...onical.com>,
        Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next][V2] io_uring: Fix incorrect sizeof operator for
 copy_from_user call

On 6/15/21 2:00 PM, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Static analysis is warning that the sizeof being used is should be
> of *data->tags[i] and not data->tags[i]. Although these are the same
> size on 64 bit systems it is not a portable assumption to assume
> this is true for all cases.  Fix this by using a temporary pointer
> tag_slot to make the code a clearer.
> 
> Addresses-Coverity: ("Sizeof not portable")
> Fixes: d878c81610e1 ("io_uring: hide rsrc tag copy into generic helpers")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Reviewed-by: Pavel Begunkov <asml.silence@...il.com>

> ---
> V2: Use temp variable tag_slot, this makes code clearer as suggested by
>     Pavel Begunkov.
> ---
>  fs/io_uring.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index d665c9419ad3..7538d0878ff5 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -7230,8 +7230,10 @@ static int io_rsrc_data_alloc(struct io_ring_ctx *ctx, rsrc_put_fn *do_put,
>  	if (utags) {
>  		ret = -EFAULT;
>  		for (i = 0; i < nr; i++) {
> -			if (copy_from_user(io_get_tag_slot(data, i), &utags[i],
> -					   sizeof(data->tags[i])))
> +			u64 *tag_slot = io_get_tag_slot(data, i);
> +
> +			if (copy_from_user(tag_slot, &utags[i],
> +					   sizeof(*tag_slot)))
>  				goto fail;
>  		}
>  	}
> 

-- 
Pavel Begunkov