linux-kernel - Re: [PATCH] NFSD: Annotate struct pnfs_block_deviceaddr with __counted

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Message-ID: <bde519c9-c95d-4275-a89b-50e628446206@embeddedor.com>
Date: Wed, 28 Aug 2024 17:58:56 -0600
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Thorsten Blum <thorsten.blum@...lux.com>, chuck.lever@...cle.com,
 jlayton@...nel.org, neilb@...e.de, okorniev@...hat.com, Dai.Ngo@...cle.com,
 tom@...pey.com, kees@...nel.org, gustavoars@...nel.org
Cc: linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] NFSD: Annotate struct pnfs_block_deviceaddr with
 __counted_by()



On 28/08/24 15:42, Thorsten Blum wrote:
> Add the __counted_by compiler attribute to the flexible array member
> volumes to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
> 
> Use struct_size() instead of manually calculating the number of bytes to
> allocate for a pnfs_block_deviceaddr with a single volume.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>

Looks good --`nr_volumes` is updated just before accessing `volumes[]`.

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
--
Gustavo

> ---
>   fs/nfsd/blocklayout.c    | 6 ++----
>   fs/nfsd/blocklayoutxdr.h | 2 +-
>   2 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
> index 3c040c81c77d..08a20e5bcf7f 100644
> --- a/fs/nfsd/blocklayout.c
> +++ b/fs/nfsd/blocklayout.c
> @@ -147,8 +147,7 @@ nfsd4_block_get_device_info_simple(struct super_block *sb,
>   	struct pnfs_block_deviceaddr *dev;
>   	struct pnfs_block_volume *b;
>   
> -	dev = kzalloc(sizeof(struct pnfs_block_deviceaddr) +
> -		      sizeof(struct pnfs_block_volume), GFP_KERNEL);
> +	dev = kzalloc(struct_size(dev, volumes, 1), GFP_KERNEL);
>   	if (!dev)
>   		return -ENOMEM;
>   	gdp->gd_device = dev;
> @@ -255,8 +254,7 @@ nfsd4_block_get_device_info_scsi(struct super_block *sb,
>   	const struct pr_ops *ops;
>   	int ret;
>   
> -	dev = kzalloc(sizeof(struct pnfs_block_deviceaddr) +
> -		      sizeof(struct pnfs_block_volume), GFP_KERNEL);
> +	dev = kzalloc(struct_size(dev, volumes, 1), GFP_KERNEL);
>   	if (!dev)
>   		return -ENOMEM;
>   	gdp->gd_device = dev;
> diff --git a/fs/nfsd/blocklayoutxdr.h b/fs/nfsd/blocklayoutxdr.h
> index b0361e8aa9a7..4e28ac8f1127 100644
> --- a/fs/nfsd/blocklayoutxdr.h
> +++ b/fs/nfsd/blocklayoutxdr.h
> @@ -47,7 +47,7 @@ struct pnfs_block_volume {
>   
>   struct pnfs_block_deviceaddr {
>   	u32				nr_volumes;
> -	struct pnfs_block_volume	volumes[];
> +	struct pnfs_block_volume	volumes[] __counted_by(nr_volumes);
>   };
>   
>   __be32 nfsd4_block_encode_getdeviceinfo(struct xdr_stream *xdr,