linux-kernel - Re: [PATCH] nfs: Fix potential posix_acl refcnt leak in nfs3_set

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Date:   Mon, 20 Apr 2020 12:59:52 +0000
From:   Trond Myklebust <trondmy@...merspace.com>
To:     "akpm@...l.org" <akpm@...l.org>,
        "xiyuyang19@...an.edu.cn" <xiyuyang19@...an.edu.cn>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>,
        "agruenba@...hat.com" <agruenba@...hat.com>,
        "okir@...e.de" <okir@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "tanxin.ctf@...il.com" <tanxin.ctf@...il.com>,
        "yuanxzhang@...an.edu.cn" <yuanxzhang@...an.edu.cn>,
        "kjlu@....edu" <kjlu@....edu>
Subject: Re: [PATCH] nfs: Fix potential posix_acl refcnt leak in nfs3_set_acl

On Mon, 2020-04-20 at 14:51 +0200, Andreas Gruenbacher wrote:
> Am Mo., 20. Apr. 2020 um 14:15 Uhr schrieb Trond Myklebust <
> trondmy@...merspace.com>:
> > I don't really see any alternative to adding a 'dfalloc' to track
> > the
> > allocated dfacl separately.
> 
> Something like the attached patch should work as well.
> 
> Thanks,
> Andreas
> 
> ---
>  fs/nfs/nfs3acl.c | 32 ++++++++++++++++++--------------
>  1 file changed, 18 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
> index c5c3fc6e6c60..f1581f11c220 100644
> --- a/fs/nfs/nfs3acl.c
> +++ b/fs/nfs/nfs3acl.c
> @@ -253,37 +253,41 @@ int nfs3_proc_setacls(struct inode *inode,
> struct posix_acl *acl,
>  
>  int nfs3_set_acl(struct inode *inode, struct posix_acl *acl, int
> type)
>  {
> -	struct posix_acl *alloc = NULL, *dfacl = NULL;
> +	struct posix_acl *orig = acl, *dfacl = NULL;
>  	int status;
>  
>  	if (S_ISDIR(inode->i_mode)) {
>  		switch(type) {
>  		case ACL_TYPE_ACCESS:
> -			alloc = dfacl = get_acl(inode,
> ACL_TYPE_DEFAULT);
> -			if (IS_ERR(alloc))
> -				goto fail;
> +			dfacl = get_acl(inode, ACL_TYPE_DEFAULT);
> +			status = PTR_ERR(dfacl);
> +			if (IS_ERR(dfacl))
> +				goto out;
>  			break;
>  
>  		case ACL_TYPE_DEFAULT:
>  			dfacl = acl;
> -			alloc = acl = get_acl(inode, ACL_TYPE_ACCESS);
> -			if (IS_ERR(alloc))
> -				goto fail;
> +			acl = get_acl(inode, ACL_TYPE_ACCESS);
> +			status = PTR_ERR(acl);
> +			if (IS_ERR(acl))
> +				goto out;
>  			break;
>  		}
>  	}
>  
>  	if (acl == NULL) {
> -		alloc = acl = posix_acl_from_mode(inode->i_mode,
> GFP_KERNEL);
> -		if (IS_ERR(alloc))
> -			goto fail;
> +		acl = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
> +		status = PTR_ERR(acl);
> +		if (IS_ERR(acl))
> +			goto out;
>  	}
>  	status = __nfs3_proc_setacls(inode, acl, dfacl);
> -	posix_acl_release(alloc);
> +out:
> +	if (acl != orig)
> +		posix_acl_release(acl);
> +	if (dfacl != orig)
> +		posix_acl_release(dfacl);
>  	return status;
> -
> -fail:
> -	return PTR_ERR(alloc);
>  }
>  
>  const struct xattr_handler *nfs3_xattr_handlers[] = {
> 
> base-commit: ae83d0b416db002fe95601e7f97f64b59514d936

Well, that should Oops when either IS_ERR(acl) or IS_ERR(dfacl)
triggers, shouldn't it? 🙂

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@...merspace.com