From: Daehyeon Ko <4ncienth@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Jens Axboe <axboe@kernel.dk>, Keith Busch <kbusch@kernel.org>,
Hannes Reinecke <hare@kernel.org>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] iov_iter: validate extracted segment for bvec alignment
Date: Fri, 16 Oct 2026 11:44:37 +0900 [thread overview]
Message-ID: <20261016024439.4069212-1-4ncienth@gmail.com> (raw)
In-Reply-To: <20261015181702.21329d323eb40d145a6d0c9d@linux-foundation.org>
Yes for bio-based drivers, but not necessarily for blk-mq hardware drivers.
The worst effect I have confirmed is an alignment-contract bypass. An
unprivileged O_DIRECT preadv() produced bvecs with offset/length pairs
(1, 4095) and (0, 1). The bio reached brd_submit_bio(), and the read
completed 4096 bytes instead of failing with -EINVAL.
I have not demonstrated harmful behavior on real DMA hardware. For a
normal blk-mq target, blk_mq_submit_bio() calls __bio_split_to_limits(),
where bio_split_io_at() rejects the misaligned bvec before queue_rq().
Virtio-blk and loop both returned -EINVAL in my controls.
So a bio-based driver can receive a bvec which violates its advertised
dma_alignment, but any further effect is driver-specific. I have not
reproduced memory corruption or a crash on real hardware.
prev parent reply other threads:[~2026-10-16 2:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 6:19 [PATCH v2] iov_iter: validate extracted segment for bvec alignment Daehyeon Ko
2026-10-16 1:17 ` Andrew Morton
2026-10-16 2:44 ` Daehyeon Ko [this message]
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