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Date: Mon, 18 May 2026 08:44:14 -0600
From: Keith Busch <kbusch@kernel.org>
To: Keith Busch <kbusch@meta.com>
Cc: axboe@kernel.dk, hch@lst.de, linux-block@vger.kernel.org
Subject: Re: [PATCHv2] blk-mq: check for stale cached request in
 blk_mq_submit_bio
Message-ID: <agslvk4DLD0OOVLR@kbusch-mbp>
References: <20260501174120.403960-1-kbusch@meta.com>
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In-Reply-To: <20260501174120.403960-1-kbusch@meta.com>

On Fri, May 01, 2026 at 10:41:19AM -0700, Keith Busch wrote:
> When submitting a bio to blk-mq, if the task should sleep after peeking
> a cached request, but before it pops it, the plug flushes and calls
> blk_mq_free_plug_rqs, freeing the cached_rqs. This creates a
> use-after-free bug. Fix this by ensuring the cached_rqs still contains
> our peeked request, and retry the bio submission without it if the
> request had been freed.

Any thoughts on this one? I know it's an old bug, but I've only recently
started seeing it happen for some reason.