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

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Message-ID: <998d25a6ac673063fe1b0def62af90792379c4fe.camel@kernel.org>
Date: Wed, 28 Aug 2024 18:09:54 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Thorsten Blum <thorsten.blum@...lux.com>, chuck.lever@...cle.com, 
	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 Wed, 2024-08-28 at 23:42 +0200, 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>
> ---
>  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,

Acked-by: Jeff Layton <jlayton@...nel.org>