linux-kernel - Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num

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Message-ID: <20251201072727.GA20845@lst.de>
Date: Mon, 1 Dec 2025 08:27:27 +0100
From: Christoph Hellwig <hch@....de>
To: Chaitanya Kulkarni <chaitanyak@...dia.com>
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
	Keith Busch <kbusch@...nel.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
	Christoph Hellwig <hch@....de>,
	Mike Christie <michael.christie@...cle.com>,
	"linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
	Jens Axboe <axboe@...nel.dk>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys
 values

On Mon, Dec 01, 2025 at 07:11:31AM +0000, Chaitanya Kulkarni wrote:
> On 11/27/25 07:54, Stefan Hajnoczi wrote:
> > The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> > Reservation Report command has a u32 maximum length. Reject num_keys
> > values that are too large to fit.
> >
> > This will become important when pr_read_keys() is exposed to untrusted
> > userspace via an <linux/pr.h> ioctl.
> >
> > Signed-off-by: Stefan Hajnoczi<stefanha@...hat.com>
> > ---
> >   drivers/nvme/host/pr.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> > index ca6a74607b139..156a2ae1fac2e 100644
> > --- a/drivers/nvme/host/pr.c
> > +++ b/drivers/nvme/host/pr.c
> > @@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
> >   	int ret, i;
> >   	bool eds;
> >   
> > +	/* Check that keys fit into u32 rse_len */
> > +	if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
> > +		return -EINVAL;
> 
> de-referencing res in res->regctl_eds[0] is safe in this patch ?

sizeof does not dereference pointers in the expression.