linux-kernel - Re: [PATCH next] audit: fix potential double free on error path from fsnotify_add_inode

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Date:   Mon, 22 Aug 2022 10:50:50 +0200
From:   Jan Kara <jack@...e.cz>
To:     Gaosheng Cui <cuigaosheng1@...wei.com>
Cc:     paul@...l-moore.com, eparis@...hat.com, mszeredi@...hat.com,
        jack@...e.cz, amir73il@...il.com, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] audit: fix potential double free on error path from
 fsnotify_add_inode_mark

On Mon 22-08-22 10:29:05, Gaosheng Cui wrote:
> Audit_alloc_mark() assign pathname to audit_mark->path, on error path
> from fsnotify_add_inode_mark(), fsnotify_put_mark will free memory
> of audit_mark->path, but the caller of audit_alloc_mark will free
> the pathname again, so there will be double free problem.
> 
> Fix this by resetting audit_mark->path to NULL pointer on error path
> from fsnotify_add_inode_mark().
> 
> Fixes: 7b1293234084d ("fsnotify: Add group pointer in fsnotify_init_mark()")
> Signed-off-by: Gaosheng Cui <cuigaosheng1@...wei.com>

Good spotting! The patch looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  kernel/audit_fsnotify.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/audit_fsnotify.c b/kernel/audit_fsnotify.c
> index 6432a37ac1c9..c565fbf66ac8 100644
> --- a/kernel/audit_fsnotify.c
> +++ b/kernel/audit_fsnotify.c
> @@ -102,6 +102,7 @@ struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pa
>  
>  	ret = fsnotify_add_inode_mark(&audit_mark->mark, inode, 0);
>  	if (ret < 0) {
> +		audit_mark->path = NULL;
>  		fsnotify_put_mark(&audit_mark->mark);
>  		audit_mark = ERR_PTR(ret);
>  	}
> -- 
> 2.25.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR