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authorIan Campbell <Ian.Campbell@citrix.com>2012-01-04 09:34:49 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2012-01-25 16:13:19 -0800
commitee1f334f2f580ff09f7c1f83be46aa2bbb4d5f6a (patch)
treedf6b0f0406f99d140edbfb6dc179ddc30d7ee69e /include
parent312544d8eac340d3ada92dbd2c60c63d229fbcf6 (diff)
xen/xenbus: Reject replies with payload > XENSTORE_PAYLOAD_MAX.
commit 9e7860cee18241633eddb36a4c34c7b61d8cecbc upstream. Haogang Chen found out that: There is a potential integer overflow in process_msg() that could result in cross-domain attack. body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH); When a malicious guest passes 0xffffffff in msg->hdr.len, the subsequent call to xb_read() would write to a zero-length buffer. The other end of this connection is always the xenstore backend daemon so there is no guest (malicious or otherwise) which can do this. The xenstore daemon is a trusted component in the system. However this seem like a reasonable robustness improvement so we should have it. And Ian when read the API docs found that: The payload length (len field of the header) is limited to 4096 (XENSTORE_PAYLOAD_MAX) in both directions. If a client exceeds the limit, its xenstored connection will be immediately killed by xenstored, which is usually catastrophic from the client's point of view. Clients (particularly domains, which cannot just reconnect) should avoid this. so this patch checks against that instead. This also avoids a potential integer overflow pointed out by Haogang Chen. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Cc: Haogang Chen <haogangchen@gmail.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'include')
-rw-r--r--include/xen/interface/io/xs_wire.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/xen/interface/io/xs_wire.h b/include/xen/interface/io/xs_wire.h
index f6f07aa35af5..7cdfca24eafb 100644
--- a/include/xen/interface/io/xs_wire.h
+++ b/include/xen/interface/io/xs_wire.h
@@ -87,4 +87,7 @@ struct xenstore_domain_interface {
XENSTORE_RING_IDX rsp_cons, rsp_prod;
};
+/* Violating this is very bad. See docs/misc/xenstore.txt. */
+#define XENSTORE_PAYLOAD_MAX 4096
+
#endif /* _XS_WIRE_H */