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Date: Tue, 24 Mar 2026 07:53:08 +0100
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Dan Carpenter <dan.carpenter@linaro.org>,
	Sungwoo Kim <iam@sung-woo.kim>, Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
	Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Subject: Re: [PATCH] nvme: remove bogus check in nvme_pr_read_keys()
Message-ID: <20260324065308.GA1578@lst.de>
References: <ab5yUf3BqtlN3K-P@stanley.mountain> <acF-E8csusg-YbaO@kbusch-mbp>
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On Mon, Mar 23, 2026 at 11:53:23AM -0600, Keith Busch wrote:
> On Sat, Mar 21, 2026 at 01:26:25PM +0300, Dan Carpenter wrote:
> > This check for if (rse_len > U32_MAX) is confusing because if
> > rse_len is > INT_MAX, that will trigger a WARN() in kvzalloc().
> > Fortunately, the caller blkdev_pr_read_keys(), puts a limit on num_keys.
> > The number of keys can't be more than PR_KEYS_MAX (65536) and the
> > condition is impossible.
> 
> There's actually two callers: blkdev_pr_read_keys() ensures the number of
> keys is smaller than 65536 and iblock_pr_read_keys() is a fixed size at
> 16. But begs the question, what guarantee does nvme_pr_read_keys() have
> that all the callers validated the number of keys such that it can
> bravely skip checking it? I think nvme should validate that it's a
> reasonable value before calling kvalloc so we return an apporpriate
> EINVAL instead of ENOMEM. The existing UINT_MAX check is certainly far
> too high, but I think something like a 4MB payload would be a totally
> reasonable upper limit for nvme on this function.

Agreed.