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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>
This commit is contained in:
Jan Beulich 2021-02-15 08:56:44 +01:00 committed by Juergen Gross
parent 7c77474b2d
commit 871997bc9e
1 changed files with 16 additions and 10 deletions
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26
drivers/block/xen-blkback/blkback.c
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@ -794,8 +794,13 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
pages[i]->persistent_gnt = persistent_gnt;
} else {
if (gnttab_page_cache_get(&ring->free_pages,
&pages[i]->page))
goto out_of_memory;
&pages[i]->page)) {
gnttab_page_cache_put(&ring->free_pages,
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;
@ -880,17 +885,18 @@ 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__);
gnttab_page_cache_put(&ring->free_pages, 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)