linux-kernel - Re: [PATCH] Fix size argument to memset call in nfsacl

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Date:	Thu, 03 Feb 2011 18:37:19 -0600
From:	Milton Miller <miltonm@....com>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Neil Brown <neilb@...e.de>, bfields@...ldses.org
Subject: Re: [PATCH] Fix size argument to memset call in nfsacl_encode

On Thu, 3 Feb 2011 about 20:41:05 +0100 (CET), Jesper Juhl wrote:
> On Thu, 3 Feb 2011, Trond Myklebust wrote:
> > On Thu, 2011-02-03 at 20:15 +0100, Jesper Juhl wrote: 
> > > We want to give memset() the sizeof(struct posix_acl), not
> > > sizeof(struct posix_acl *).
> > > 
> > > Signed-off-by: Jesper Juhl <jj@...osbits.net>
> > > ---
> > >  nfsacl.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/nfs_common/nfsacl.c b/fs/nfs_common/nfsacl.c
> > > index 84c27d6..bc6d81b 100644
> > > --- a/fs/nfs_common/nfsacl.c
> > > +++ b/fs/nfs_common/nfsacl.c
> > > @@ -117,7 +117,7 @@ int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
> > >  		 * invoked in contexts where a memory allocation failure is
> > >  		 * fatal.  Fortunately this fake ACL is small enough to
> > >  		 * construct on the stack. */
> > > -		memset(acl2, 0, sizeof(acl2));
> > > +		memset(acl2, 0, sizeof(*acl2));
> > >  		posix_acl_init(acl2, 4);
> > >  
> > >  		/* Insert entries in canonical order: other orders seem
> > 
> > Ccing Milton Miller who also sent in the same patch.
> > 
> > Neither patch is correct afaics. posix_acl_init() will clobber the above
> > memset, and so the correct fix is just to get rid of it...
> > 
> 
> posix_acl_init() sets a_refcount and a_count, but what about a_entries ... 
> no problem, nfsacl_encode() itself takes care of that post the 
> posix_acl_init() call.. it's all good.
> 
> So ...
> 
> 
> Remove pointless memset() in nfsacl_encode().
> 

It would be nice to point out that the memset was just added and of
a incorrect size.

> Thanks to Trond Myklebust <Trond.Myklebust@...app.com> for pointing out 
> that it is not needed since posix_acl_init() will set everything 
> regardless..
> 

But I ack the patch since I even pointed out this alternative in my
changelog.  I guess that could be Reported-by.

http://lkml.indiana.edu/hypermail/linux/kernel/1102.0/00665.html

> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  nfsacl.c |    1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/nfs_common/nfsacl.c b/fs/nfs_common/nfsacl.c
> index 84c27d6..ec0f277 100644
> --- a/fs/nfs_common/nfsacl.c
> +++ b/fs/nfs_common/nfsacl.c
> @@ -117,7 +117,6 @@ int nfsacl_encode(struct xdr_buf *buf, unsigned int base, struct inode *inode,
>  		 * invoked in contexts where a memory allocation failure is
>  		 * fatal.  Fortunately this fake ACL is small enough to
>  		 * construct on the stack. */
> -		memset(acl2, 0, sizeof(acl2));
>  		posix_acl_init(acl2, 4);
>  
>  		/* Insert entries in canonical order: other orders seem
> 
> 
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