linux-kernel - Re: [V9fs-developer] [Patch] 9p: fix a potential acl leak

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Date:   Wed, 14 Dec 2016 09:57:48 +0100
From:   Greg Kurz <groug@...d.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     linux-kernel@...r.kernel.org, Latchesar Ionkov <lucho@...kov.net>,
        Ron Minnich <rminnich@...dia.gov>, jack@...e.cz,
        Eric Van Hensbergen <ericvh@...il.com>, salyzyn@...roid.com,
        v9fs-developer@...ts.sourceforge.net
Subject: Re: [V9fs-developer] [Patch] 9p: fix a potential acl leak

On Tue, 13 Dec 2016 10:33:34 -0800
Cong Wang <xiyou.wangcong@...il.com> wrote:

> posix_acl_update_mode() could possibly clear 'acl', if so
> we leak the memory pointed by 'acl'. Save this pointer
> before calling posix_acl_update_mode() and release the memory
> if 'acl' really gets cleared.
> 
> Reported-by: Mark Salyzyn <salyzyn@...roid.com>
> Reviewed-by: Jan Kara <jack@...e.cz>
> Cc: Eric Van Hensbergen <ericvh@...il.com>
> Cc: Ron Minnich <rminnich@...dia.gov>
> Cc: Latchesar Ionkov <lucho@...kov.net>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---

Reviewed-by: Greg Kurz <groug@...d.org>

>  fs/9p/acl.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/9p/acl.c b/fs/9p/acl.c
> index b3c2cc7..082d227 100644
> --- a/fs/9p/acl.c
> +++ b/fs/9p/acl.c
> @@ -277,6 +277,7 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
>  	case ACL_TYPE_ACCESS:
>  		if (acl) {
>  			struct iattr iattr;
> +			struct posix_acl *old_acl = acl;
>  
>  			retval = posix_acl_update_mode(inode, &iattr.ia_mode, &acl);
>  			if (retval)
> @@ -287,6 +288,7 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
>  				 * by the mode bits. So don't
>  				 * update ACL.
>  				 */
> +				posix_acl_release(old_acl);
>  				value = NULL;
>  				size = 0;
>  			}