[PATCH 5.4 09/13] xen-blkback: dont "handle" error by BUG()

Greg Kroah-Hartman
2021-02-22T12:33:52Z

From: Jan Beulich <jbeulich@suse.com>

commit 5a264285ed1cd32e26d9de4f3c8c6855e467fd63 upstream.

In particular -ENOMEM may come back here, from set_foreign_p2m_mapping().
Don't make problems worse, the more that handling elsewhere (together
with map's status fields now indicating whether a mapping wasn't even
attempted, and hence has to be considered failed) doesn't require this
odd way of dealing with errors.

This is part of XSA-362.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/block/xen-blkback/blkback.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -867,10 +867,8 @@ again:
break;
}

- if (segs_to_map) {
+ if (segs_to_map)
ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
- BUG_ON(ret);
- }

/*
* Now swizzle the MFN in our domain with the MFN from the other domain
@@ -885,7 +883,7 @@ again:
pr_debug("invalid buffer -- could not remap it\n");
put_free_pages(ring, &pages[seg_idx]->page, 1);
pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
- ret |= 1;
+ ret |= !ret;
goto next;
}
pages[seg_idx]->handle = map[new_map_idx].handle;