[SRU][Bionic][Cosmic][PATCH 1/1] xen-netback: fix input validation in xenvif_set_hash_mapping()

Kleber Sacilotto de Souza kleber.souza at canonical.com
Fri Oct 19 09:46:04 UTC 2018


From: Jan Beulich <JBeulich at suse.com>

Both len and off are frontend specified values, so we need to make
sure there's no overflow when adding the two for the bounds check. We
also want to avoid undefined behavior and hence use off to index into
->hash.mapping[] only after bounds checking. This at the same time
allows to take care of not applying off twice for the bounds checking
against vif->num_queues.

It is also insufficient to bounds check copy_op.len, as this is len
truncated to 16 bits.

This is XSA-270 / CVE-2018-15471.

Reported-by: Felix Wilhelm <fwilhelm at google.com>
Signed-off-by: Jan Beulich <jbeulich at suse.com>
Reviewed-by: Paul Durrant <paul.durrant at citrix.com>
Tested-by: Paul Durrant <paul.durrant at citrix.com>
Cc: stable at vger.kernel.org [4.7 onwards]
Signed-off-by: David S. Miller <davem at davemloft.net>

CVE-2018-15471
(cherry picked from commit 780e83c259fc33e8959fed8dfdad17e378d72b62)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
---
 drivers/net/xen-netback/hash.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/xen-netback/hash.c b/drivers/net/xen-netback/hash.c
index 3c4c58b9fe76..3b6fb5b3bdb2 100644
--- a/drivers/net/xen-netback/hash.c
+++ b/drivers/net/xen-netback/hash.c
@@ -332,20 +332,22 @@ u32 xenvif_set_hash_mapping_size(struct xenvif *vif, u32 size)
 u32 xenvif_set_hash_mapping(struct xenvif *vif, u32 gref, u32 len,
 			    u32 off)
 {
-	u32 *mapping = &vif->hash.mapping[off];
+	u32 *mapping = vif->hash.mapping;
 	struct gnttab_copy copy_op = {
 		.source.u.ref = gref,
 		.source.domid = vif->domid,
-		.dest.u.gmfn = virt_to_gfn(mapping),
 		.dest.domid = DOMID_SELF,
-		.dest.offset = xen_offset_in_page(mapping),
-		.len = len * sizeof(u32),
+		.len = len * sizeof(*mapping),
 		.flags = GNTCOPY_source_gref
 	};
 
-	if ((off + len > vif->hash.size) || copy_op.len > XEN_PAGE_SIZE)
+	if ((off + len < off) || (off + len > vif->hash.size) ||
+	    len > XEN_PAGE_SIZE / sizeof(*mapping))
 		return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
 
+	copy_op.dest.u.gmfn = virt_to_gfn(mapping + off);
+	copy_op.dest.offset = xen_offset_in_page(mapping + off);
+
 	while (len-- != 0)
 		if (mapping[off++] >= vif->num_queues)
 			return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
-- 
2.17.1





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