Re: [PATCH] ide: set an upper limit to nb_sectors - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: P J P <ppandit@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>
Cc: Prasad J Pandit <pjp@fedoraproject.org>,
	John Snow <jsnow@redhat.com>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Markus Armbruster <armbru@redhat.com>
Subject: Re: [PATCH] ide: set an upper limit to nb_sectors
Date: Tue, 19 Jan 2021 15:13:10 +0100	[thread overview]
Message-ID: <b0198f13-c5af-70c5-59cb-c34bac328b83@redhat.com> (raw)
In-Reply-To: <20210119134211.494133-1-ppandit@redhat.com>

Hi Prasad,

On 1/19/21 2:42 PM, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
> 
> Set an upper limit to number of sectors on an IDE disk media.
> This is to ensure that logical block addresses (LBA) and
> nb_sector arguments remain within INT_MAX range.
> 
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/ide/core.c | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> Update: limit s->nb_sectors count
>   -> https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04270.html
>   -> https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04173.html
> 
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index b49e4cfbc6..064998804a 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -1161,15 +1161,21 @@ static void ide_cfata_metadata_write(IDEState *s)
>                                      s->nsector << 9), 0x200 - 2));
>  }
> 
> +static void ide_set_nb_sectors(IDEState *s)
> +{
> +    uint64_t nb_sectors;
> +
> +    blk_get_geometry(s->blk, &nb_sectors);

       /* An explanation here would be useful */

or better, add a self-explaining definition for this magic value.

> +    s->nb_sectors = MIN(nb_sectors, (uint64_t)INT_MAX << 2);
> +}