linux-kernel - Re: [PATCH v2] audit: fix a memory leak bug

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Message-ID: <CAHC9VhQNGiw_+KhZPC7DhzS83u3gi+Ch1AKCeZitsFg=98gUDA@mail.gmail.com>
Date:   Fri, 19 Apr 2019 15:28:39 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Wenwen Wang <wang6495@....edu>
Cc:     Eric Paris <eparis@...hat.com>,
        "moderated list:AUDIT SUBSYSTEM" <linux-audit@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] audit: fix a memory leak bug

On Fri, Apr 19, 2019 at 11:10 AM Wenwen Wang <wang6495@....edu> wrote:
>
> In audit_rule_change(), audit_data_to_entry() is firstly invoked to
> translate the payload data to the kernel's rule representation. In
> audit_data_to_entry(), depending on the audit field type, an audit tree may
> be created in audit_make_tree(), which eventually invokes kmalloc() to
> allocate the tree.  Since this tree is a temporary tree, it will be then
> freed in the following execution, e.g., audit_add_rule() if the message
> type is AUDIT_ADD_RULE or audit_del_rule() if the message type is
> AUDIT_DEL_RULE. However, if the message type is neither AUDIT_ADD_RULE nor
> AUDIT_DEL_RULE, i.e., the default case of the switch statement, this
> temporary tree is not freed.
>
> To fix this issue, only allocate the tree when the type is AUDIT_ADD_RULE
> or AUDIT_DEL_RULE.
>
> Signed-off-by: Wenwen Wang <wang6495@....edu>
> ---
>  kernel/auditfilter.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)

This looks good, it just needs some minor vertical whitespace fixes (see below).

> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 63f8b3f..923b858 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1114,22 +1114,28 @@ int audit_rule_change(int type, int seq, void *data, size_t datasz)
>         int err = 0;
>         struct audit_entry *entry;
>
> -       entry = audit_data_to_entry(data, datasz);
> -       if (IS_ERR(entry))
> -               return PTR_ERR(entry);
> -
>         switch (type) {
>         case AUDIT_ADD_RULE:
> +               entry = audit_data_to_entry(data, datasz);
> +               if (IS_ERR(entry))
> +                       return PTR_ERR(entry);
> +

I realize you are taking the blank line from the code above, but we
probably don't need it here.

>                 err = audit_add_rule(entry);
>                 audit_log_rule_change("add_rule", &entry->rule, !err);
>                 break;
> +

Definitely do not add this blank line.

>         case AUDIT_DEL_RULE:
> +               entry = audit_data_to_entry(data, datasz);
> +               if (IS_ERR(entry))
> +                       return PTR_ERR(entry);
> +
>                 err = audit_del_rule(entry);
>                 audit_log_rule_change("remove_rule", &entry->rule, !err);
>                 break;
> +

Same here.

>         default:
> -               err = -EINVAL;
>                 WARN_ON(1);
> +               return -EINVAL;
>         }
>
>         if (err || type == AUDIT_DEL_RULE) {
> --
> 2.7.4

-- 
paul moore
www.paul-moore.com