Re: [PATCHv2] io_uring: avoid page allocation warnings

From: Jens Axboe
Date: Wed May 01 2019 - 12:00:59 EST

On 5/1/19 9:59 AM, Mark Rutland wrote:
> In io_sqe_buffer_register() we allocate a number of arrays based on the
> iov_len from the user-provided iov. While we limit iov_len to SZ_1G,
> we can still attempt to allocate arrays exceeding MAX_ORDER.
> On a 64-bit system with 4KiB pages, for an iov where iov_base = 0x10 and
> iov_len = SZ_1G, we'll calculate that nr_pages = 262145. When we try to
> allocate a corresponding array of (16-byte) bio_vecs, requiring 4194320
> bytes, which is greater than 4MiB. This results in SLUB warning that
> we're trying to allocate greater than MAX_ORDER, and failing the
> allocation.
> Avoid this by using kvmalloc() for allocations dependent on the
> user-provided iov_len. At the same time, fix a leak of imu->bvec when
> registration fails.

Applied, thanks.

Jens Axboe