Re: [Xen-devel] [PATCH] tools/xenstore: fix a use after free problem in xenstored

[Jürgen Groß <jgross@xxxxxxxx>]

Ping?

On 24.03.20 11:12, Juergen Gross wrote:
> Commit 562a1c0f7ef3fb ("tools/xenstore: dont unlink connection object
> twice") introduced a potential use after free problem in
> domain_cleanup(): after calling talloc_unlink() for domain->conn
> domain->conn is set to NULL. The problem is that domain is registered
> as talloc child of domain->conn, so it might be freed by the
> talloc_unlink() call.
>
> Fixes: 562a1c0f7ef3fb ("tools/xenstore: dont unlink connection object twice")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>   tools/xenstore/xenstored_domain.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tools/xenstore/xenstored_domain.c 
> b/tools/xenstore/xenstored_domain.c
> index baddaba5df..5858185211 100644
> --- a/tools/xenstore/xenstored_domain.c
> +++ b/tools/xenstore/xenstored_domain.c
> @@ -214,6 +214,7 @@ static void domain_cleanup(void)
>   {
>         xc_dominfo_t dominfo;
>         struct domain *domain;
> +       struct connection *conn;
>         int notify = 0;
>   
>    again:
> @@ -230,8 +231,10 @@ static void domain_cleanup(void)
>                                 continue;
>                 }
>                 if (domain->conn) {
> -                       talloc_unlink(talloc_autofree_context(), domain->conn);
> +                       /* domain is a talloc child of domain->conn. */
> +                       conn = domain->conn;
>                         domain->conn = NULL;
> +                       talloc_unlink(talloc_autofree_context(), conn);
>                         notify = 0; /* destroy_domain() fires the watch */
>                         goto again;
>                 }