The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 166d3863231667c4f64dee72b77d1102cdfad11f Mon Sep 17 00:00:00 2001 From: Demi Marie Obenour demi@invisiblethingslab.com Date: Sun, 10 Jul 2022 19:05:22 -0400 Subject: [PATCH] xen/gntdev: Ignore failure to unmap INVALID_GRANT_HANDLE

The error paths of gntdev_mmap() can call unmap_grant_pages() even though not all of the pages have been successfully mapped. This will trigger the WARN_ON()s in __unmap_grant_pages_done(). The number of warnings can be very large; I have observed thousands of lines of warnings in the systemd journal.

Avoid this problem by only warning on unmapping failure if the handle being unmapped is not INVALID_GRANT_HANDLE. The handle field of any page that was not successfully mapped will be INVALID_GRANT_HANDLE, so this catches all cases where unmapping can legitimately fail.

Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()") Cc: stable@vger.kernel.org Suggested-by: Juergen Gross jgross@suse.com Signed-off-by: Demi Marie Obenour demi@invisiblethingslab.com Reviewed-by: Oleksandr Tyshchenko oleksandr_tyshchenko@epam.com Reviewed-by: Juergen Gross jgross@suse.com Link: https://lore.kernel.org/r/20220710230522.1563-1-demi@invisiblethingslab.com Signed-off-by: Juergen Gross jgross@suse.com

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 4b56c39f766d..84b143eef395 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -396,13 +396,15 @@ static void __unmap_grant_pages_done(int result, unsigned int offset = data->unmap_ops - map->unmap_ops;

for (i = 0; i < data->count; i++) { - WARN_ON(map->unmap_ops[offset+i].status); + WARN_ON(map->unmap_ops[offset + i].status != GNTST_okay && + map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE); pr_debug("unmap handle=%d st=%d\n", map->unmap_ops[offset+i].handle, map->unmap_ops[offset+i].status); map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE; if (use_ptemod) { - WARN_ON(map->kunmap_ops[offset+i].status); + WARN_ON(map->kunmap_ops[offset + i].status != GNTST_okay && + map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE); pr_debug("kunmap handle=%u st=%d\n", map->kunmap_ops[offset+i].handle, map->kunmap_ops[offset+i].status);