git: dfb372f5d38c - stable/12 - xen-blkback: fix leak of grant maps on ring setup failure

[Ed Maste]

The branch stable/12 has been updated by emaste:

URL: https://cgit.FreeBSD.org/src/commit/?id=dfb372f5d38c302953a6a4e2838179cd0a1a6438

commit dfb372f5d38c302953a6a4e2838179cd0a1a6438
Author:     Roger Pau Monné <royger at FreeBSD.org>
AuthorDate: 2021-01-20 18:40:51 +0000
Commit:     Ed Maste <emaste at FreeBSD.org>
CommitDate: 2021-02-23 00:57:03 +0000

    xen-blkback: fix leak of grant maps on ring setup failure
    
    Multi page rings are mapped using a single hypercall that gets passed
    an array of grants to map. One of the grants in the array failing to
    map would lead to the failure of the whole ring setup operation, but
    there was no cleanup of the rest of the grant maps in the array that
    could have likely been created as a result of the hypercall.
    
    Add proper cleanup on the failure path during ring setup to unmap any
    grants that could have been created.
    
    This is part of XSA-361.
    
    Sponsored by:   Citrix Systems R&D
    
    (cherry picked from commit 808d4aad1022a2a33d222663b0c9badde30b9d45)
---
 sys/dev/xen/blkback/blkback.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/sys/dev/xen/blkback/blkback.c b/sys/dev/xen/blkback/blkback.c
index d935ba965b00..b98ccb6e2595 100644
--- a/sys/dev/xen/blkback/blkback.c
+++ b/sys/dev/xen/blkback/blkback.c
@@ -2912,10 +2912,31 @@ xbb_connect_ring(struct xbb_softc *xbb)
 	     ring_idx < xbb->ring_config.ring_pages;
 	     ring_idx++, gnt++) {
 		if (gnt->status != 0) {
+			struct gnttab_unmap_grant_ref unmap[XBB_MAX_RING_PAGES];
+			unsigned int i, j;
+
 			xbb->ring_config.va = 0;
 			xenbus_dev_fatal(xbb->dev, EACCES,
 					 "Ring shared page mapping failed. "
 					 "Status %d.", gnt->status);
+
+			/* Unmap everything to avoid leaking grant table maps */
+			for (i = 0, j = 0; i < xbb->ring_config.ring_pages;
+			    i++) {
+				if (gnts[i].status != GNTST_okay)
+					continue;
+
+				unmap[j].host_addr = gnts[i].host_addr;
+				unmap[j].dev_bus_addr = gnts[i].dev_bus_addr;
+				unmap[j++].handle = gnts[i].handle;
+			}
+			if (j != 0) {
+				error = HYPERVISOR_grant_table_op(
+				    GNTTABOP_unmap_grant_ref, unmap, j);
+				if (error != 0)
+					panic("Unable to unmap grants (%d)",
+					    error);
+			}
 			return (EACCES);
 		}
 		xbb->ring_config.handle[ring_idx]   = gnt->handle;