From fbb5d5edd233c25774109dc0a673702c7b4985e5 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Fri, 25 Feb 2022 16:05:41 +0100 Subject: [PATCH] xen/netfront: don't use gnttab_query_foreign_access() for mapped status Commit 31185df7e2b1d2fa1de4900247a12d7b9c7087eb upstream. It isn't enough to check whether a grant is still being in use by calling gnttab_query_foreign_access(), as a mapping could be realized by the other side just after having called that function. In case the call was done in preparation of revoking a grant it is better to do so via gnttab_end_foreign_access_ref() and check the success of that operation instead. This is CVE-2022-23037 / part of XSA-396. Reported-by: Demi Marie Obenour Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 56c7f2ebf573..d1bcbc24a70b 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -414,14 +414,12 @@ static bool xennet_tx_buf_gc(struct netfront_queue *queue) queue->tx_link[id] = TX_LINK_NONE; skb = queue->tx_skbs[id]; queue->tx_skbs[id] = NULL; - if (unlikely(gnttab_query_foreign_access( - queue->grant_tx_ref[id]) != 0)) { + if (unlikely(!gnttab_end_foreign_access_ref( + queue->grant_tx_ref[id], GNTMAP_readonly))) { dev_alert(dev, "Grant still in use by backend domain\n"); goto err; } - gnttab_end_foreign_access_ref( - queue->grant_tx_ref[id], GNTMAP_readonly); gnttab_release_grant_reference( &queue->gref_tx_head, queue->grant_tx_ref[id]); queue->grant_tx_ref[id] = GRANT_INVALID_REF; -- 2.20.1