From: Jan Beulich jbeulich@suse.com
commit 871997bc9e423f05c7da7c9178e62dde5df2a7f8 upstream.
The function uses a goto-based loop, which may lead to an earlier error getting discarded by a later iteration. Exit this ad-hoc loop when an error was encountered.
The out-of-memory error path additionally fails to fill a structure field looked at by xen_blkbk_unmap_prepare() before inspecting the handle which does get properly set (to BLKBACK_INVALID_HANDLE).
Since the earlier exiting from the ad-hoc loop requires the same field filling (invalidation) as that on the out-of-memory path, fold both paths. While doing so, drop the pr_alert(), as extra log messages aren't going to help the situation (the kernel will log oom conditions already anyway).
This is XSA-365.
Signed-off-by: Jan Beulich jbeulich@suse.com Reviewed-by: Juergen Gross jgross@suse.com Reviewed-by: Julien Grall julien@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 | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-)
--- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -843,8 +843,11 @@ again: pages[i]->page = persistent_gnt->page; pages[i]->persistent_gnt = persistent_gnt; } else { - if (get_free_page(ring, &pages[i]->page)) - goto out_of_memory; + if (get_free_page(ring, &pages[i]->page)) { + put_free_pages(ring, pages_to_gnt, segs_to_map); + ret = -ENOMEM; + goto out; + } addr = vaddr(pages[i]->page); pages_to_gnt[segs_to_map] = pages[i]->page; pages[i]->persistent_gnt = NULL; @@ -928,17 +931,18 @@ next: } segs_to_map = 0; last_map = map_until; - if (map_until != num) + if (!ret && map_until != num) goto again;
- return ret; - -out_of_memory: - pr_alert("%s: out of memory\n", __func__); - put_free_pages(ring, pages_to_gnt, segs_to_map); - for (i = last_map; i < num; i++) +out: + for (i = last_map; i < num; i++) { + /* Don't zap current batch's valid persistent grants. */ + if(i >= last_map + segs_to_map) + pages[i]->persistent_gnt = NULL; pages[i]->handle = BLKBACK_INVALID_HANDLE; - return -ENOMEM; + } + + return ret; }
static int xen_blkbk_map_seg(struct pending_req *pending_req)