On 6/15/21 12:35 PM, Colin Ian King wrote:
> On 15/06/2021 12:30, Pavel Begunkov wrote:
>> 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@xxxxxxxxxxxxx>
>>>>
>>>> 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@xxxxxxxxxxxxx>
>>>> ---
>>>> 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));
>>
> BTW, Coverity is complaining about:
>
> 7220 return -ENOMEM;
>
> Wrong sizeof argument (SIZEOF_MISMATCH)
>
> suspicious_sizeof: Passing argument nr * 8UL /* sizeof
> (data->tags[0][0]) */ to function io_alloc_page_table and then casting
> the return value to u64 ** is suspicious.
>
> 7221 data->tags = (u64 **)io_alloc_page_table(nr *
> sizeof(data->tags[0][0]));
Ah, this one. We want it to be indexed linearly, but can't allocate
as much, so together with io_get_tag_slot() it hides two level
tables from us, providing linear indexing.
>
> Not sure if that's a false positive or not. This kind of indirection
> makes my brain melt.
So, this one should be a false positive. But agree about the
indirection, it's not the first sizeof bug you found. Any
better ideas how to push it to the type system?
I think something like below would make more sense
#define copy_from_user_typed(from, to) \
assert(typeof(from) == typeof(to)),
copy_from_user(from, to, sizeof(*from));
--
Pavel Begunkov
