On 2/20/23 7:53 AM, Gabriel Krisman Bertazi wrote:
> Pavel Begunkov <asml.silence@xxxxxxxxx> writes:
>
>> If two or more mappings go back to back to each other they can be passed
>> into io_uring to be registered as a single registered buffer. That would
>> even work if mappings came from different sources, e.g. it's possible to
>> mix in this way anon pages and pages from shmem or hugetlb. That is not
>> a problem but it'd rather be less prone if we forbid such mixing.
>>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
>> ---
>> io_uring/rsrc.c | 15 ++++++++-------
>> 1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
>> index a59fc02de598..70d7f94670f9 100644
>> --- a/io_uring/rsrc.c
>> +++ b/io_uring/rsrc.c
>> @@ -1162,18 +1162,19 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages)
>> pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM,
>> pages, vmas);
>> if (pret == nr_pages) {
>> + struct file *file = vmas[0]->vm_file;
>> +
>> /* don't support file backed memory */
>> for (i = 0; i < nr_pages; i++) {
>> - struct vm_area_struct *vma = vmas[i];
>> -
>> - if (vma_is_shmem(vma))
>> + if (vmas[i]->vm_file != file)
>> + break;
>
> Perhaps, return -EINVAL instead of -EOPNOTSUPP
Agree, -EOPNOTSUPP is OK for an unsupported case, but I think
-EINVAL makes more sense for the weird case of mixed sources
as it's unlikely to ever make sense to support that.
--
Jens Axboe
