--- /dev/null
+From b7649f4e1d73402aaf46cb8260df6161b101b593 Mon Sep 17 00:00:00 2001
+From: Jan Beulich <jbeulich@suse.com>
+Date: Fri, 26 Mar 2021 16:28:57 +0100
+Subject: xen-blkback: don't leak persistent grants from xen_blkbk_map()
+
+From: Jan Beulich <jbeulich@suse.com>
+
+commit a846738f8c3788d846ed1f587270d2f2e3d32432 upstream.
+
+The fix for XSA-365 zapped too many of the ->persistent_gnt[] entries.
+Ones successfully obtained should not be overwritten, but instead left
+for xen_blkbk_unmap_prepare() to pick up and put.
+
+This is XSA-371.
+
+Signed-off-by: Jan Beulich <jbeulich@suse.com>
+Cc: stable@vger.kernel.org
+Reviewed-by: Juergen Gross <jgross@suse.com>
+Reviewed-by: Wei Liu <wl@xen.org>
+Signed-off-by: Juergen Gross <jgross@suse.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/block/xen-blkback/blkback.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/drivers/block/xen-blkback/blkback.c
++++ b/drivers/block/xen-blkback/blkback.c
+@@ -937,7 +937,7 @@ next:
+ out:
+ for (i = last_map; i < num; i++) {
+ /* Don't zap current batch's valid persistent grants. */
+- if(i >= last_map + segs_to_map)
++ if(i >= map_until)
+ pages[i]->persistent_gnt = NULL;
+ pages[i]->handle = BLKBACK_INVALID_HANDLE;
+ }