Patch-mainline: v5.12-rc1
Git-commit: 871997bc9e423f05c7da7c9178e62dde5df2a7f8
References: XSA-365 CVE-2021-26930 bsc#1181843
From: Jan Beulich <jbeulich@suse.com>
Date: Mon, 15 Feb 2021 08:56:44 +0100
Subject: [PATCH 9/9] xen-blkback: fix error handling in xen_blkbk_map()
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>
---
drivers/block/xen-blkback/blkback.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 1558f68512de..a703f365b5b1 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -843,8 +843,11 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
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 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
}
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)
--
2.26.2