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

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Message-ID: <d606818f-2e13-fbea-970b-eab9080d7f15@gmail.com>
Date:   Tue, 15 Jun 2021 12:30:54 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Colin Ian 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] io_uring: Fix incorrect sizeof operator for
 copy_from_user call

On 6/15/21 11:47 AM, Colin Ian King wrote:
> On 15/06/2021 11:45, 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.
>>
>> 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>
>> ---
>>  fs/io_uring.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index d665c9419ad3..6b1a70449749 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -7231,7 +7231,7 @@ static int io_rsrc_data_alloc(struct io_ring_ctx *ctx, rsrc_put_fn *do_put,
>>  		ret = -EFAULT;
>>  		for (i = 0; i < nr; i++) {
>>  			if (copy_from_user(io_get_tag_slot(data, i), &utags[i],
>> -					   sizeof(data->tags[i])))
>> +					   sizeof(*data->tags[i])))
>>  				goto fail;
>>  		}
>>  	}
>>

Yep, thanks Colin. I think `sizeof(io_get_tag_slot(data, i))`
would be less confusing. Or

u64 *tag_slot = io_get_tag_slot(data, i);
copy_from_user(tag_slot, ..., sizeof(*tag_slot));

-- 
Pavel Begunkov