From: Juergen Gross <jgross@suse.com>
Date: Thu, 5 May 2022 06:35:31 +0000 (+0200)
Subject: xen/grant-table: never put a reserved grant on the free list
X-Git-Tag: v6.1-rc5~1139^2~26
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=8c9eb0e3731d7140abc77cd80aeeeea8c2ff325e;p=platform%2Fkernel%2Flinux-starfive.git

xen/grant-table: never put a reserved grant on the free list

Make sure a reserved grant is never put on the free list, as this could
cause hard to debug errors.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
---

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 6ea31ea..1a1aec0 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -207,6 +207,10 @@ static inline void check_free_callbacks(void)
 static void put_free_entry(grant_ref_t ref)
 {
 	unsigned long flags;
+
+	if (unlikely(ref < GNTTAB_NR_RESERVED_ENTRIES))
+		return;
+
 	spin_lock_irqsave(&gnttab_list_lock, flags);
 	gnttab_entry(ref) = gnttab_free_head;
 	gnttab_free_head = ref;