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Subject: Re: [PATCHv2] io_uring: avoid page allocation warnings
To:     Mark Rutland <mark.rutland@arm.com>, linux-kernel@vger.kernel.org
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org
References: <20190501155916.34008-1-mark.rutland@arm.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <7c75a9bf-204f-1159-a2db-4679158652a2@kernel.dk>
Date:   Wed, 1 May 2019 10:00:41 -0600
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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