From: Keith Busch <kbusch@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <kbusch@meta.com>,
linux-block@vger.kernel.org, axboe@kernel.dk,
Carlos Maiolino <cem@kernel.org>
Subject: Re: [PATCH] block: check bio split for unaligned bvec
Date: Mon, 15 Jun 2026 16:08:41 -0600 [thread overview]
Message-ID: <ajB36Wt9lU_F-r7h@kbusch-mbp> (raw)
In-Reply-To: <20260615133549.GC26132@lst.de>
On Mon, Jun 15, 2026 at 03:35:49PM +0200, Christoph Hellwig wrote:
> On Fri, Jun 12, 2026 at 03:32:04PM -0700, Keith Busch wrote:
> > From: Keith Busch <kbusch@kernel.org>
> >
> > Offsets and lengths need to be validated against the dma alignment. This
> > check was skipped for sufficiently a small bio with a single bvec, which
> > may allow an invalid request dispatched to the driver. Force the
> > validation for an unaligned bvec by forcing the bio split path that
> > handles this condition.
>
> This fix itself looks good, but we'll also need something similar
> for bio-based drivers that never call into the splitting helper.
Totally agree. I'm looking at all the .submit_bio drivers, and I think
they fall into one of four catagories:
1: already split (md/nvme-mp/drbd; dm conditional)
2: don't split
* btt, dcssblk: already reject unaligned
* n64cart: WARNs, but potentially proceeds to undefined behavior
* nfhd: silently corrupts, but looks like a driver problem
3: can handle arbitrary memory but advertise default dma_alignment=511
(brd, pmem, zram, ps3vram, simdisk - "limits lie")
4: forward/self-split (bcache)
I think the block layer can fix 3 with a BLK_FEAT flag to allow a zero
dma_alignment limit for the drivers that really don't need it from the
source buffer.
As for the rest, I don't know of anyone caring to ensure n64 or nfhd are
correctly handling degenerate applications.
next prev parent reply other threads:[~2026-06-15 22:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-12 22:32 [PATCH] block: check bio split for unaligned bvec Keith Busch
2026-06-13 12:36 ` Jens Axboe
2026-06-15 9:37 ` Carlos Maiolino
2026-06-15 13:35 ` Christoph Hellwig
2026-06-15 22:08 ` Keith Busch [this message]
2026-06-16 15:36 ` Keith Busch
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