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

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Date:   Mon, 20 Apr 2020 14:13:17 +0000
From:   Trond Myklebust <trondmy@...merspace.com>
To:     "agruenba@...hat.com" <agruenba@...hat.com>
CC:     "okir@...e.de" <okir@...e.de>,
        "tanxin.ctf@...il.com" <tanxin.ctf@...il.com>,
        "xiyuyang19@...an.edu.cn" <xiyuyang19@...an.edu.cn>,
        "akpm@...l.org" <akpm@...l.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>,
        "kjlu@....edu" <kjlu@....edu>,
        "yuanxzhang@...an.edu.cn" <yuanxzhang@...an.edu.cn>
Subject: Re: [PATCH] nfs: Fix potential posix_acl refcnt leak in nfs3_set_acl

On Mon, 2020-04-20 at 15:51 +0200, Andreas Gruenbacher wrote:
> nfs3_set_acl keeps track of the acl it allocated locally to determine
> if an acl
> needs to be released at the end.  This results in a memory leak when
> the
> function allocates an acl as well as a default acl.  Fix by releasing
> acls
> that differ from the acl originally passed into nfs3_set_acl.
> 
> Fixes: b7fa0554cf1b ("[PATCH] NFS: Add support for NFSv3 ACLs")
> Reported-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
> ---
>  fs/nfs/nfs3acl.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
> index c5c3fc6e6c60..26c94b32d6f4 100644
> --- a/fs/nfs/nfs3acl.c
> +++ b/fs/nfs/nfs3acl.c
> @@ -253,37 +253,45 @@ 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, *alloc;
>  	int status;
>  
>  	if (S_ISDIR(inode->i_mode)) {
>  		switch(type) {
>  		case ACL_TYPE_ACCESS:
> -			alloc = dfacl = get_acl(inode,
> ACL_TYPE_DEFAULT);
> +			alloc = get_acl(inode, ACL_TYPE_DEFAULT);
>  			if (IS_ERR(alloc))
>  				goto fail;
> +			dfacl = alloc;
>  			break;
>  
>  		case ACL_TYPE_DEFAULT:
> -			dfacl = acl;
> -			alloc = acl = get_acl(inode, ACL_TYPE_ACCESS);
> +			alloc = get_acl(inode, ACL_TYPE_ACCESS);
>  			if (IS_ERR(alloc))
>  				goto fail;
> +			dfacl = acl;
> +			acl = alloc;
>  			break;
>  		}
>  	}
>  
>  	if (acl == NULL) {
> -		alloc = acl = posix_acl_from_mode(inode->i_mode,
> GFP_KERNEL);
> +		alloc = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
>  		if (IS_ERR(alloc))
>  			goto fail;
> +		acl = alloc;
>  	}
>  	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);
> +	status = PTR_ERR(alloc);
> +	goto out;
>  }
>  
>  const struct xattr_handler *nfs3_xattr_handlers[] = {
> 
> base-commit: ae83d0b416db002fe95601e7f97f64b59514d936

Thanks Andreas! This one looks good.

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