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Thu, 15 Oct 2026 19:44:59 -0700 (PDT) From: Daehyeon Ko <4ncienth@gmail.com> To: Andrew Morton Cc: Alexander Viro , Jens Axboe , Keith Busch , Hannes Reinecke , 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 Message-ID: <20261016024439.4069212-1-4ncienth@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261015181702.21329d323eb40d145a6d0c9d@linux-foundation.org> References: <20261015061907.2713943-1-4ncienth@gmail.com> <20261015181702.21329d323eb40d145a6d0c9d@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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.